Journal of Engineering Geology

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Introduction
Improving the mechanical behavior of clay soil by stabilization agents is a mean of fulfilling geotechnical design criteria. The method of stabilization can be divided into chemical, mechanical, or a combination of both methods. Chemical stabilization is performed by adding chemical agents such as cement, lime or fly ash to the soil (Bahar et al., 2004). Soil reinforcement is one of the mechanical methods that is used for improving the behavior of soils (Tang et al., 2007). Reinforcement of soil achieved by either inclusion of strips, bars, grids and etc. within a soil mass in a preferred direction or mixing discrete fibers randomly with a soil mass.
Mixing of cement with soil is made a production that is called soil-cement and results in chemical reaction between soil, cement, and water. The compressive strength of soil-cement is increased by increasing the cement content and this leads to brittle behavior or sudden failure. On the other hand, by increasing the cement to soil ratio for cohesive soils, shrinkage micro-cracks may develop in the soil as a result of the loss of water content during drying or hydration of cement. Therefore, if the tensile strength of these materials is not sufficient cracks will develop under loading and damage will be resulted (Khattak and Alrashidi, 2006). Consoli et al. (2003) and Tang et al. (2007) indicated that adding the fiber to soil can prevent from occurrence of these cracks and increases the tensile strength of the soil.
The focus of this paper is on the statistical analysis of the results and development of regression models. Regression relationships are developed based on the experimental results that were presented by Estabragh et al. (2017). These relationships relate the compressive and tensile strengths of the soil to percent of used fiber, cement and curing time.
Material and methods of testing
Unconfined compression and tensile strength tests were carried on unreinforced and reinforced soil, soil cement according to ASTM standards. Samples of soil-cement were made by mixing a clay soil and two different weight percent of cement (8 and 10%). Reinforced soil samples were also prepared by mixing 0.5 and 1 weight percent of Polypropylene fibers with 10, 15, 20 and 25 mm lengths. The dry unit weight and water content of prepared samples were the same as optimum water content and maximum dry unit weight that were resulted from standard compaction test. The compressive and tensile strength tests were conducted on the samples by considering the curing time according to ASTM standards until the failure of the sample is achieved.
Results and discussion
The experimental tests showed that reinforcement of the soil and soil cement increase the peak compressive and tensile strength. The peak compressive strength of reinforced soil is increased by increasing the fiber content at a constant length of the fiber. It can be said that by increasing the percent of fiber, the number of fibers in the sample is increased and contact between soil particle and fibers is increased which result in increase in the strength (Maher 1994). However, by increasing the length of the constant fiber inclusion there will be no significant increase in strength because the number of shorter fiber is more than longer fiber in a specific sample (Ahmad et al., 2010). Inclusion of fibers can greatly increase the tensile strength of clay soil. In addition to reinforcement of soil cement showed the same trend. When fiber is added to soil cement, the surface of fiber adheres to the hydration products of cement and some clay particle. Therefore, this combination increases the efficiency of load transfer from the composition to the fibers which increase the peak strength (Tang et al., 2007). In addition, the tensile strength shows the same trend.
Based on the experimental data on the behavior of a randomly reinforced clay soil and soil cement multiple regression models (linear and non-linear) were developed for calculating the peak compressive and tensile strength (dependent variables) based on the value of the coefficient of determination (R²). The proposed regression models were functions of independent variables including weight percent of fiber, length of fiber (length/diameter of fiber), weight percent of cement, and curing time. Finally, the comparison is made between the predicted results from proposed models and experimental results. In order to investigate the model accuracy, the Root Mean Square Error (RMSE) and Normalized Root Mean Square Error (NRMSE) are used.
 The Multiple Linear Regression models (MLR) was very suitable for the study of the effect of independent variables on the quantitative analytic dependent variable. The NRSME for peak compressive and tensile strength is was 3.59% and 5.11% respectively for these models. Also, the Multiple Nonlinear Regression models (MNLR) had a much lower error than the linear model because of the quadratic equation, the equation will be able to predict the increase and decrease of the output variable in terms of the increase of the independent input variable. Therefore, The NRMSE for peak compressive and tensile strength was 1.02% and 4.04% for MNLR models respectively.
Conclusion
The following conclusions can be drawn from this study:
- The strength of reinforced soil and soil cement is increased by increasing the fiber content.
- Increasing the length of the fibers in the soil and soil cement has no significant effect on increasing the peak compressive strength, but it will be effective in increasing the tensile strength.
- The Multiple Nonlinear Regression models (MNLR) have more accuracy for prediction of output variable (peak strength) because of lower normalized root mean square error../files/site1/files/131/7Extended_Abstract.pdf


 

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Introduction
In regard to consumptions of oil materials by human, soil contamination causes worriness in environment and geotechnics areas in previous years, such that studying of soils lead to soil refine, soil bearing capacity and soil changing by infiltration of contamination. The rates of problems on environment are different and it depends on soil types and its structure, organic materials values, soil permeability, climate and type of contamination. In viewpoint of geotechnics, many investigations have been done on various contaminated soils that their result leads to optimum application of those as road construction and decrease of costs. In this research, with adding of different percentages of gasoil into the soil, engineering properties of contaminated soils were investigated and its effect on the erodibility of soils was studied. Regarding to the Hamedan oil storages complex extension and lateral installations, the study of contaminated soils are essential. Also, because the location of that complex is at urban area, the environmental risk of leaking of oil materials is available. Thus, the goal of this research is to investigate the erodibility of contaminated soils at the studied area.     
Material and methods
Hamedan oil storages complex is located about 17.7 km far from Hamedan city. In order to study engineering geological properties and erodibility of three layers of soils in studied area, the soil samplings were done from three soil layers. Based on the field and laboratory results, all of three soil layers were classified into SM class and had too much lime (Table 1). Testing program is divided into engineering geological tests and erodibility tests. All of the engineering geological tests on the uncontaminated and contaminated soils were undertaken according to ASTM (2000) (Table 2). In order to prepare the contaminated soils and to determine the maximum absorbable gasoil, the soil samples were contaminated by gasoil and some standard compaction tests were undertaken on the soils. According to the test results, upper and lower layers were saturated by 19% of gasoil and middle layer was saturated by 15% of gasoil. After determination of gasoil saturations percentages for studied soil layers, the 7, 13 and 19 percentages of gasoil were added into the upper and lower layers and the 5, 10 and 15 percentages of gasoil were added into the middle layer. Thus, for engineering geological tests, 9 samples of contaminated soils were prepared.   
Table 1. Soil properties of studied area

Lime percentage	Soil type	PI%	PL%	LL%	Sample	Layer
85.15	SM	8.99	40.65	49.64	L1	Upper
62.16	SM	15.49	32.12	47.61	L2	Middle
88.72	SM	15.46	27.14	42.60	L3	Lower

Table 2. Engineering geological tests according to ASTM (2000)

Standard No.	Test type
ASTM-D422 (2000)	Soil classification
ASTM-D4318-87 (2000)	Atterberg limits
ASTM-D698 (2000)	Standard Compaction
ASTM-D3080 (2000)	ِDirect shear
ASTM-D2166-87 (2000)	Uniaxial Compressive Strength

To prepare the sample for direct shear test, a mould with dimension of 10 cm *10 cm *2 cm was used. Then, the prepared sample was set inside the shear box and vertical stress was applied. All of direct shear tests were done in unconsolidated-undrained condition (UU), in maximum dry unit weight _dmax) and in optimum water content _{( opt})of soil samples.
All of the soil samples for uniaxial compressive strength tests were prepared in maximum dry unit weight and optimum water content. To prepare the soil samples, a split tube mould with 5*10 cm of dimensions was used. Based on that test, the soil samples are set under axial load and failure occurred at the end of the test.
To investigate the effect of gasoil on soil erodibility, first the erodibility tests by using rainfall simulator were done on uncontaminated soils and then, on contaminated soil with different percentages of gasoil. All of soil samples for erodibility test were prepared into the pans with 30*30*15 cm of dimensions and in maximum dry unit weight and optimum water content. The thickness of soil samples were 5 cm and the gravelly drainage layers were 10 cm. The rainfall intensity was equal to rainfall intensity of sampling area (29 mm/hours) and the steepness of soil samples were equals to sampling area steepness (10 to 40 degrees). After catching of runoff and drained water, the eroded soils were weighted and the weight loss of soil samples was calculated.   
Results and discussion
All of the engineering geological tests results are shown in Table 3. With increasing of the gasoil percentages, dry maximum unit weights of all three layers have decrease trends while the optimum water contents have increase trends. Surrounding of the soil grains by gasoil and water causes the easy sliding of grains and more compaction. The Atterberg test results shows that liquid and plasticity limits of soil had increase trend with increasing the gasoil. In the middle layer its trend is more than the others. Because the viscosity of gasoil is more than the water viscosity, the adhesion of contaminated soil would be more than the uncontaminated soil and then, the liquid and plasticity limits of contaminated soils are more than the others. The uniaxial compressive strength results show that the undrained strength of contaminated soils would be decrease with increasing the gasoil content. This behavior is the result of sliding of the contaminated soil grains on each other.
The results of erodibility tests results are shown in Table 4. The erodibility would be increase with increasing the gasoil percentages. Also, it would be increase with steepness dips degrees. In compare to the uncontaminated soils, the maximum weight loss of the contaminated soil is 608.3 kg/m².hr in 15% of gasoil and 40 degrees of steepness in L2 layer. The minimum weight loss of the contaminated soil is 13.33 kg/m².hr in 0% of gasoil and 10 degrees of steepness in L3 layer. Thus, the assessment of gasoil effect on erodibility of soils is very important.
Table 3. Results of the engineering geological tests on the uncontaminated and contaminated soil samples

Layers	Gasoil percentage	Liquid limit (%)	Plasticity limit (%)	Plasticity Index (%)	Maximum  dry unit  weight  (g/cm3)	Optimum water content (%)	Internal friction angle (ɸ)	Cohesion (kPa)	Uniaxial compressive strength (kPa)
L1	0%	49.64	40.65	8.99	1.65	22	4.6	7.4	18.4
	7%	54	40.13	13.87	1.87	10.5	4.04	6.6	8.7
	13%	55.67	43.71	11.95	1.88	8.5	3.26	3.7	7.8
	19%	55	40.65	14.34	1.96	3	2.3	2.75	3.5
L2	0%	47.61	32.12	15.49	1.87	14	6.97	6	9.6
	5%	64	40.39	23.61	2.08	9	5.73	5.5	7
	10%	66	46.63	19.37	2.11	6	5.15	4	6.1
	15%	68	49.09	18.91	2.14	3.5	4	2	1.25
L3	0%	42.6	27.14	15.46	1.62	22.3	2.6	10.7	22.6
	7%	56	39.27	16.72	1.92	9.5	2.41	8.5	10.5
	13%	57.18	41.66	15.51	2.01	6	2.17	7/3	7.8
	19%	63	42	20.99	2.03	3	1.45	6.9	4.4

 
Table 4. Results of the uncontaminated and contaminated soils in different steepness*

Layer	Gasoil percentage	Dip of 10◦	Dip of 20◦	Dip of 30◦	Dip of 40◦
L1	0%	56.4	70.4	73.2	111.06
	7%	149.6	178.8	248.4	202.53
	13%	166.53	227.2	241.6	278.93
	19%	227.86	256.66	419.86	334.66
L2	0%	30.8	102.53	156.53	317.73
	5%	58.66	142.66	151.2	324.8
	10%	74.93	168.66	244.53	365.73
	15%	105.73	283.73	359.86	608.13
L3	0%	13.33	75.06	79.46	86.26
	7%	55.2	98.53	78.13	81.06
	13%	124.13	176.8	145.73	140.06
	19%	196.4	279.46	200.93	210

Conclusion
1. According to the grain size analysis test results, all of three layers of soils around the Hamedan oil storage are SM with too much lime.
2. With increasing the gasoil, liquid and plasticity limits of three soil layers had increase trend. its trend in the middle layer is more than the others.
3. According to the erodibility results of contaminated soils, the weight loss of middle layer was more than the other layers because of the middle soil layer had lower percentages of lime.   
4. The gasoil causes decrease of soil strength and increase of weight losing. Thus, the uniaxial compressive strength and weight losing have reverse correlation.  
5. With increasing of the contamination, the cohesion and internal friction angle of soils would be decrease and then, the erodibility would be increase.
6. Maximum of erosion of contaminated soils was in 15 and 19 percentages of gasoil and it was three times more than that of uncontaminated soils.
7. The critical steepness of uncontaminated soil layers was 40 degrees for all three layers, but it was different for contaminated soils, 
8. Regarding to the location of Hamedan oil storages, the environmental risk of oil leakages and erodibility of contaminated soils are certain.  
./files/site1/files/132/5Extended_Abstracts.pdf

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Introduction
The dispersivity phenomenon occurs due to the dissolution of some of the ions in clay soils or against the shear stress of normal water flow in cohesion-less soils. Water surface flows in low slopes cause surface erosion of dispersive soils. Dispersivity in the soil starts from a point and gradually expands; the starting point can be the holes from the activity of the animals, the existing cracks or the growth path of the roots of the plants. There is a lot of field evidence to recognize the dispersivity of the loess soils. In field investigations, soil dispersivity can be detected according to the following parameters: geological origin of the loess soil, mineralogical composition, gradation, drainage pattern, slaking of agglomerates, specific morphology, high permeability, geographical area (length and width relative to origin), soil color, relationship between slope and soil erosion, precipitation, erosion of column cracks, heeling, mud flowing runoff and the presence of salt crystals in loess soils. In terms of sedimentological characteristics and engineering geological properties, Golestan loesses have been dispersed in three areas 1, 2 and 3, which are consistent with the loesses of clay, silt, and sand types, respectively.
Material and methods
Loess soils in three regions of east and northeast of Golestan province were sampled. Sampling was conducted in two forms of wax-coated agglomerates and metallic cylindrical tubes. Depth of sampling follows the foundation of the buildings located on the Mehr Housing site and the Cheshme Lee village, varying from 0.5 to 2 meters. On the path of the Beqqeje Bala village, sampling was carried out from the path trench. After transferring to the laboratory, samples were subjected to gradation testing, Atterberg limits test to determine the unit weight of the volume and density.
The pinhole test was done on samples with the unit weight of normal volume (g_n) and maximum volume (g_dmax) and its rate of dispersion was determined. The research background, field evidence and the results of laboratory experiments indicate the dispersion of soil sampling areas. The results show that soil compaction reduces the severity of dispersion and decreases the flow rate, so that the flow rate has decreased in the Maravehtapeh sample by 38%, in the Cheshmeli sample by 13% and in the Beqqeje Bala sample by 43%. Compaction cannot eliminate the dispersion of soil. Adding nanoclay decreases the severity of soil dispersion and eliminates its dispersion properties in most cases.
In order to evaluate the effect of nanoclay on severity and to decrease the dispersion property of soil with ratios of 0.5, 1, 2, 3, 4 and 5 wt%, of Montmorillonite Nanoclay was added.
The nanoclay used in the present research was selected from the Sigma-Aldrich America Company called montmorillonite nanoclay and was purchased from its domestic representative, i.e. Iranian Nanomaterials Pioneers Company. The product has a density of 300 to 370 kilograms per cubic meter and a particle size of between 1 and 2 nm. The specific surface area of the nanoparticle is about 250 square meters per gram. Its color in normal light and in 1 to 2% moisture is yellow to yellowish buff.
Results and discussion
The rate of dispersion of samples with nanoclay was measured in Pinhole Test Apparatus. Also, the method of mixing nanoclay with dispersive soil shows different behaviors in severity of dispersion and its reduction. Given that the specific surface of nanoclay is high and this property can include the whole surface of soil grains as a sticky coating and increase soil cohesion, the mixing method is practically one of the most important steps in examining the effect of nanoclay on soil stabilization. At ratios of 0.5, 1, 2, 3, 4 and 5 wt% of nanoclay, nanoclay was mixed with soils of sampling regions by four methods:
In the method A, they were completely mixed with the preparation of a homogeneous mud from soil and nanoclay via an electric mixer.
In the method B, mixing of loess soil with nanoclay was performed in optimum water content.
In the method C, mixing of loess soil with nanoclay was conducted in the form of dough by hand mixer. In the method D, mixing of loess soil with nanoclay was carried out in the form of vibration dry by grading sieve shaker.
After mixing with nanoclay in the desired method (four methods A, B, C, D), the samples were first stored in sealed plastic containers for 24 hours. Then, the samples containing nanoclay were reconstructed in cylindrical mold of the pinhole device with the unit weight of maximum dry volume and moisture of two percent higher than the optimum moisture content and a hole was created in the middle of it. The samples remained in this position for 24 hours, and then the test was performed. Testing was carried out on each sample according to the standard D4647-93, and flow rate reading was done over a period of two minutes to 18 minutes.
Conclusion
The conclusion of this study shows that the three loess samples taken have a dispersivity potential and the flow rate is low in the unit weight of maximum volume, but the dispersivity potential does not eliminate. Adding nanoclay with any weight ratio reduces the flow rate and eliminates the soil dispersivity potential.
The results of this survey showed that 1% nanoclay weight ratio is technically and economically the most appropriate mixing ratio. With this weight ratio, the method of preparing homogeneous mud with an electric mixer (method A) produces the lowest flow rate, so that the flow rate from 1.3 ml per second in pure soil to 0.3 ml per second in the soil containing nanoclay is reduced by 50 mm. Therefore, it can be said that this method is more suitable, but it is not operationally efficient and the method B is more appropriate. In the method B, the flow rate reaches from 1.3 to 0.55 ml per second.

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Introduction
Estimation of Liquefaction is one of the main objectives in geotechnical engineering. For this purpose, several numerical and experimental methods have been proposed. An important stage to predict the liquefaction is the prediction of excess pore water pressure at a given point. In general, there are two important methods for soil dynamics analyses, fully coupled effective stress and uncoupled total stress analysis. The main purpose of this study is to evaluate the model capacity of the finite difference software, FLAC, based on effective stress analysis methods to predict the excess pore water pressure during seismic loading. A level ground centrifuge test conducted during the VELACS project on the Nevada sand with a density of 40%, was utilized to calibrate the numerical model. After the validation of the numerical model, a model was conducted to predict excess pore pressure and consequently the liquefaction for the site of Bandar Abbas Mosque.
Theoretical bases
A fully coupled u–P formulation, where pore pressures and displacements are computed simultaneously and interactively at each time step, is used in FLAC software. This feature is used to simulate the excess pore water pressure time histories during cyclic loading.
The finite difference based software, FLAC, used the Finn model that incorporates two equations correlating the volumetric strain induced by the cyclic shear strain and excess pore water pressure produced during cyclic loading. As mentioned above, the pore water pressure generation can be computed from two sets of equations: Martin et al. (1975) and the Byrne (1991) formulations in which the volumetric strain that was produced in any cycle of loading is depended on the shear strain that was formed during that cycle as well as the previously accumulated volumetric strain.
Modeling and Results
The VELACS model # 1 centrifuge test representing a level ground site constituted of the Nevada sand at 40% relative density has been numerically simulated in the current study to validate the numerical model. The centrifuge model contains a laminar box with slipping “rings” that allows differential horizontal displacements. This was simulated in the FLAC model by free-field boundary conditions which prevent reflection of the waves in the side walls. Figure 1 shows comparison of EPWP time histories ratio of numerical modeling and centrifuge test. Static analysis was carried out before dynamic analysis in order to find initial stress and strain state. At the next stage, the dynamic loads were applied at the base of the model and dynamic analysis was performed. The Bandar Abbas mosque project is located approximately 500 meters from the coast. In the project, due to the groundwater level and the existence of loose layers of silt, investigating the potential of liquefaction is necessary.
For numerical modeling the results of the general soil mechanics test on soil samples and standard penetration test performed on the site were used to calibrate the parameters and select the model constants.
Conclusion
The results of numerical modeling have been matched to experimental results of the centrifuge test using both Martin and Byrne formulations, except for the case of 5 m the numerical model has predicted lower excess pore water pressure values than the experimental values. This may be originated from the fundamental assumption of the Martin et al. (1975) EPWP theory, in which excess pore water pressure is directly related to the relevant volume changes. On the other hand, the Martin et al. (1975) model was adopted for one-dimensional measures of shear strain, while, in a 2D analysis under both horizontal and vertical shakings, there are three strain rate measures. FLAC uses some assumptions to solve this problem and it can affect the results.
The results of the numerical model showed liquefaction to a depth of about 5 meters that is almost compatible with the results from the lab, which has declared that the depth 2 to 5 m is liquefiable.
With careful selection of numerical model parameters one can generally use the simulation results to have a general sense on the pore water pressure generation and liquefaction prediction.
./files/site1/files/134/5.pdf

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Introduction
The geotechnical engineering problems involving unsaturated soils are included water flow, shear strength and volume change. Soil-water characteristic curve (SWCC) describes the constitutive relationship between soil suction and soil water content. SWCC may be determined directly or indirectly in the laboratory. Because of the various difficulties involved in the direct measurements, a simple and economical laboratory method namely filter paper method is of considerable value. The filter paper method is a laboratory technique that has recently been accepted as a standard method of measuring soil potential, reaching far higher ranges of water potential in comparison to other techniques, and is based on the principle of moisture absorption by filter paper until there is a balance in potential between filter paper and soil.
This paper presents an experimental investigation performed to evaluate the soil water characteristic curves of dune sand stabilized with SBR polymer and MICP processes (Sporosarcina pasteurii bacteria with CaCl2 and urea) with contact filter paper method in the Jabal Kandi area.
Material and methods
The dune sand used in this study was obtained from the surface (0–10 cm depth) of Jabal kandi area, located on the south-west of Urmia Lake. SBR polymer is prepared from Paya Resin Company in Esfahan. In the MICP processes, S. pasteurii from Persian Type Culture Collection (PTCC 1645) was used as the urease positive bacterium. Cultivation of the microorganism was conducted in a medium containing 20 g l^-1 yeast extract, 10 g l^-1 NH₄Cl at a pH value of 8. Sporsarcina pasteurii was grown to late exponential phase to final concentration of 1.5 g dry weight l^-1 and urease activity of 2.2 mM urea min^-1 under aerobic batch conditions. Broth cultures were incubated in a shaker incubator operated at 120 rpm. Cementation solution of MICP consisted of CaCl2 and urea. All experiments were performed at an ambient temperature of 25^oC ± 2.
For the tests with Whatman No. 42 filter paper, three different soil samples were prepared (dune sand, dune sand stabilized with (5-10-15) % SBR polymer and dune sand stabilized with (5-10-15) % MICP process). Residual water content is 2.5% and the residual dry density is 15 kN/m³. The soil is mixed with the right quantity of water and placed in a sealed plastic bag for 24 hours to allow the hydric equilibrium to establish. The contact filter paper tests were carried out on soil specimens stabilized with SBR polymer and MICP process to the residual water content (2.5%) and nearly residual dry density (15 kN/m³). The soil specimen sizes were 50 mm in diameter and 20 mm height. The test procedure involves placing a piece of initially air dry filter paper against the soil specimen whose matric suction is required and sealing the whole to prevent evaporation. The filter paper was wetted to water content in equilibrium with the magnitude of the soil matric suction, and careful measurement of the water content of the filter paper enables the soil matric suction to be obtained from a previously established correlation. This provides a measure of the matric suction. ASTM D-5298-93 standard is used for the filter paper method.
Results and discussion
The SWCCs for dune sand stabilized with SBR polymer and MICP process under different SBR polymer and MICP process contents are illustrated in this study. Gradual transition from a unimodel SWCC to a bimodal SWCC was observed as SBR polymer and MICP process content increases. The unimodel SWCC is characterized by having two bends defining the air entry value and residual water content. The air entry value is defined as the matric suction above which air commence to enter the soil pores. The residual water content is defined as the water content beyond which no significant decrease in water content occurs. The bimodal SWCC is characterized by having four distinct bindings: two air entry values and two residual water contents. For SBR polymer and MICP process content equal to or less than 5 percent, the SWCC shows a unimodal form of SWCC. With the increase of SBR polymer and MICP process content greater than 5%, the SWCC indicate a bimodal form. It is further observed that the residual water content and the air entry value increases with the increase of SBR polymer and MICP process content. These observations are attributed to the presence of smaller pore size developed as a result of SBR polymer and MICP process particles filling the voids between sand particles. Bimodal SWCC are generally observed for gap-graded soils as well as soils that include two levels of pore sizes defined as macro pores and micro pores. Therefore, it can be inferred that the increase of SBR polymer and MICP process content, resulted in the formation of micro pores within the dune sand stabilized with SBR polymer and MICP process. The portion of the soil water characteristic curves representing macro pore sizes range between matric suction of 0.1 to 100 kPa. Whereas, the portion of the SWCC representing micro pore sizes lies between matric suction of 200 and 1500 kPa.
Summary and Conclusions
In this study, the effect of SBR polymer and MICP process content on the soil water characteristic curves of dune sand was evaluated. SBR polymer and MICP process contents considered include 0%, 5%, 10% and 15%. Results from this study indicated that, as the SBR polymer and MICP process content increased, the shape of the SWCC transforms from a unimodal form to a bimodal form. Furthermore, the air entry value and residual water content were observed to increase with increase in SBR polymer and MICP process content signifying increase in water retention capacity. The bimodal form of the SWCC indicates the presence of two levels of pore sizes; namely macro pores and micro pores. For 10% and 15% SBR polymer and MICP process content, the macro pores are considered the dominant pore size covering a broad range of the SWCC from 0.1 to 100 kPa. Therefore, it is inferred that the SWCC of dune sand stabilized with SBR polymer and MICP process are strongly related to the texture and pore size distribution of the dune sand stabilized with SBR polymer and MICP process which in turn, has a significant impact on its hydraulic characteristics.
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Introduction
Urban development and rapid extension of cities have been accompanied by a considerable growth in mechanized tunneling. The abrasivity of rock and even soil is a factor with considerable influence on the wear of tools. Soil abrasion and the resulting tool wear has a major impact on machine operation, utilization, and tunneling costs and time. One of the problematic aspects of working in abrasive grounds is the frequent need for the replacement of cutting tools, especially in pressurized face tunnel boring machines (TBMs). The effect of worn and damaged TBM cutter heads has been documented for numerous tunnel projects around the world. However, the lack of a standard or universally accepted test for soil abrasivity in geotechnical investigations has made the prediction of tool wear a difficult task.
Material and methods
A reliable prognosis of the abrasiveness of soils on a project would be of great benefit for designers, clients, and contractors. Many abrasion tests exist for rocks, and some have been proposed for soils; however, there is no universally accepted or international standard test for soil abrasivity testing. One of the most important and available tests in this field is LCPC abrasivity test which was developed by the Laboratoire Central des Ponts et Chaussées in the 1980’s. The LCPC Abrasivity Coefficient (ABR or LAC) can be used as a measure for both the abrasivity of the soil material and the influence of the grain size. The  abrasivity  testing  of  rock  is  controlled  by well-known parameters, whereas in soils many factors are influencing the abrasivity such as in-situ soil conditions, sedimentary petrology and technical   properties.
Tabriz metro line 2 Project about 22 km in length that will connect eastern part of the Tabriz city to its western part, considered as a case study. The project comprises a single tunnel which has been constructed using two earth pressure balance EPB-TBM with a cutting-wheel diameter of 9.49 m. In this study, based on geological and geotechnical properties, the tunnel route was divided into four parts and the abrasion and brittleness coefficients of alluviums determined by LCPC test. Besides that, the influences of some factors such as moisture content, mineralogy, grain size and shape, type and amount of foam have been studied.
Results and discussion
Based on more than 130 LCPC test results, in general, the Tabriz Metro’s line-2 route alluviums have the abrasion in the range of low to very high and the brittleness in the range of high to very high. In order to measure the effect of moisture content on abrasion and brittleness coefficient, the LCPC test was done on some samples related to the tunnel route in dried and moistened modes (5%, 0%, 15%, 20%, 25%, and 30%). Three types of sandstone, andesite, and conglomerate of the route were used to test the effect of moisture and petrology on abrasion. In a moisture range of 0 to 5%, in all types of materials, abrasion was increased. In a moisture range of 5 to 10%, abrasion was decreased in all three types, and this shows that a moisture level of 10% is a normal moisture content to create minimum abrasion. The behavior of sandstone and conglomerate is similar at higher moisture contents, and an increase in moisture content to 30% can increase abrasion of materials in both types. In conglomerate, abrasion at higher moisture levels is significantly more than in other modes. In andesite, an increase in moisture content to 20% can increase abrasion, although the abrasion is decreased with a moisture content of over 20%. In most samples, increase in moisture content led to decrease in brittleness of materials. In general, the highest abrasion level was related to conglomerate and the lowest level was related to sandstone. Moreover, andesite was at a lower level than conglomerate and a higher level than sandstone in terms of abrasion. Also, the results show that increased grain size led to increased abrasion, and the changes in andesite were greater than in sandstone.
In order to test the effectiveness of foam on abrasion, the foam used in workshops (A 168) made by Komeil Company Kashan was used for four types of petrography: conglomerate, andesite, sandstone, and silica. This test was conducted in the range of dried to 100 ml foam. In all types, decreased abrasion is observed from 0 to 20 ml and increased abrasion is observed from 20 to 100 ml.
Conclusion
The following conclusions are drawn from this research.
- With regard to the effect of grain size, increased size of grains could lead to more abrasion and less brittleness
- In terms of the effect of mineralogy, the conglomerate had the most effect on abrasion. In terms of brittleness, andesite was the most brittle.
- When the foam is moisturized in the sample, minimum abrasion is observed and above this level, the abrasion is increased.
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In recent years, with the growing use of the nailing method for stabilizing excavation walls, there has been a need for a comprehensive investigation of the behavior of this method. In the  previous studies, the behavior of nailed walls has been investigated in static and dynamic states and under different conditions. However, due to the different feature of near-field ground motions, it is  necessary to study the effect of these motions on the behavior of the nailed walls. Near-fault ground motion is significantly affected by the earthquake record direction and the rupture mechanism. So, in this study, to compare the effects of near-field and far-field ground motions, a two-dimensional (2D) soil- nailed wall was considered. PLAXIS 2D was used for the modeling of the soil-nailed wall system. An excavation with a dimension of 10 meters in height was taken into the account. In this study, 10 records (Five fault-normal near-field ground motion records and five far-field ground motion records), were recorded  on the rock and  applied to the model. These ground motion records were derived from the near-fault ground motion record set used by Baker. These records were scaled to the Peak Ground Acceleration (PGA) of 0.35g and then applied to the bottom of the finite element models. Mohr-Coulomb model was then used to describe the soil behavior, and Elasto-plastic model was employed for the nails. A damping ratio of 0.05 was considered at the fundamental periods of the soil layer. The results showed that the  generated values of bending moment, shear force and axial force in nails under the effect of the near-fault ground motions were  more than those in the far-ault ground motions. These values were  almost equal to 23% for the maximum bending moment, 30% for the  shear force,  and 22% for the axial force. The created displacement under the effect of near-fault ground motions was  more than that in the far-fault since a higher energy was  applied to the model in the near-field ground motions during a short time (pulse-like ground motions). In contrast, in the far-fault ground motions, due to the more uniform distribution of energy during the record, such pulse-like displacements were not observed in the system response. Increasing in nail length and soil densification, decreases the displacement of the soil-nailed wall but does not change the general behavior of the soil under the effect of near-field ground motions. Based on the obtained results, for a constant PGA, there were  positive correlations between the values of the  maximum displacement on the top of the wall and  the PGV values of near-fault ground motion records. However, the mentioned correlations were  not observed in the case of far-fault ground motions.

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The increasing rate of construction activities in urban areas is accompanied by excavation in the vicinity of existing structures and urban utilities. This issue has highlighted the importance of constructing protecting structures in order to control displacements and prevent damage to structures and their neighboring area. Among the important widely used wall stabilization techniques, one can name nailing and grouted anchors. However, these methods suffer some drawbacks such as annoying noise and vibration during the drilling, implementation difficulties below the water table, grouting problem, installation of strands and bars in the borehole in porous and collapse soils, and long curing time for the grout of post-tension anchors. Since the helical anchor method lacks many of the mentioned problems, it is now widely used in many applications.
In the present work, a laboratory model of helical anchor stabilized wall is presented and evaluated. For this purpose, four types of anchors at 20° back slope are designed in a sandy soil and the effect of helix configuration (in term of its diameter and number of blades) is investigated. Considering the laboratory scale of the designed model, the results obtained using helical anchor were compared with numerical results of soil nailing wall by applying the particle image velocimetry (PIV) analyses.
Material and methods
The test box designed in this work is made of a metal plate with a thickness, length, width, and depth of 1.5 mm, 100 cm, 60 cm, and 30 cm, respectively, and a Plexiglas in its opposing side with a thickness of 50 mm. The soil used in the experiments was the dry sand of Soufian region in east Azerbaijan province of Iran. The soil is classified as SP according to USCS classification. The helical anchors were fabricated by welding the helical pitches to a metal shaft. The end part of the shafts is screw threaded such that to fasten a bolt to them.
To start the experiment, the empty box was completely cleaned using the detergents to remove any pollution or soil on the Plexiglas and metal surface. Afterward, the sandy soil was poured on the wall floor and the facing was placed inside the box vertically. Again, the sandy soil was poured from both sides of the facing up to the installation height of the helices. Helices were installed in the assigned holes and their angle was adjusted through the pre-fabricated stencils. The soil height was increased up to the next row assigned for helices installation. These steps were repeated until reach the wall crest. After preparation of the physical model, its behavior during the preparation must be modeled. We first filled both sides of the model and then modeled the stability behavior of the helical anchor wall through excavating its facing opposed side. Overall, the wall was built through eight excavation steps.
Results and discussion
The maximum displacement is related to the anchor type 1, which does not have enough bearing capacity under surcharge conditions. By changing the anchor type and increasing the number of helices, shear strains and their expansion in the wall back decline. The decrease in displacement rate by changing the anchor from type 1 to type 2 is 18%, which is due to the low bearing capacity of type 2 anchor compared to the type 1 anchor. Increasing the number of pitches from one to two (changing the type 1 anchor to type 3 anchor) showed a considerable decrease (i.e., 43%) in displacement rate. Increasing the number of pitches from 1 to 3 (changing the anchor from type 1 to type 3) resulted in a 62% decrease in wall crest displacement. This displacement decrease rate seems to decline with an increase in the number of helixes.
The displacement rate for all four anchors is almost similar in two excavation steps, which probably is because of the need for displacement for activation of the anchors. One strategy to deal this issue in the sensitive projects and control the displacement is to apply post-tension helical anchors. Then, in stages 4 to 6, the displacement was almost constant due to four main reasons including wall rigidity, the presence of reinforcements, formation of pre-step displacement-induced tension force, and enough capacity of anchors to face with more displacement. In stages 6 to 8, type 1 and 2 anchors showed growing displacements due to the reduction and ending the wall rigidity and lower bearing capacity. In type 3 and 4 anchors, the maximum displacement was related to 4 initial stages. In type 1 and 2 anchors, which have two helical plates, almost a similar behavior was observed until stage 6 of excavation, but eventually type 3 anchors showed better performance because of higher bearing capacity to overall displacement.
Conclusion
In the present study, a physical model was designed to investigate the effect of helical anchors’ geometry on displacement rate of helical anchor wall and compare it with a nail wall. Overall, comparing the results obtained by conducting these experiments on a helical anchor stabilized wall and a nail wall revealed that:
- Wall crest displacement is affected by the diameter and number of helices and decreases by an increase in bearing capacity.
- The increase in the number of pitches from one to two (single-pitch to double-pitch anchor) has a higher effect on displacement control compared to the case of changing the double-pitch to triple-pitch anchor. So, it can be stated that a further increase in the number of anchor pitches results in a declined performance of the anchors.
- All anchors need a slight displacement for activation. This issue cannot be resolved by changing the type of helical anchors. Hence, when the displacement required for activation of the anchors exceeds the allowable wall crest displacement, use of post-tensioned helical anchors is recommended.
- A comparison between nailing and helical anchor results revealed that the relative density of the wall stabilized with the helical anchor is less than that of the nail wall; and wall crest displacement in the helical anchor wall was very lower than that of nail wall. Thus, the helical anchor wall stabilization is preferred when other economic and technical requirements are met.

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Introduction
Dispersive soils are problematic and they cause a great many of local damages and destructions in hydraulic structures such as dikes and irrigation channels. The correct identification and recognition of divergence are fundamental measures taken in line with preventing the early destruction of the hydraulic structures. The soil improvement using lime, especially in clayey soils (CL), brings about an increase in the optimum moisture percentage, reduction of the maximum dry unit weight, reduction of swelling potential, increase in the strength and elasticity module. The effect of lime on soil can be classified into two groups, namely short and long-term stabilization. Raise of the soil’s workability is counted amongst the short-term modification measures and it is the most important factor in the early improvement stages. The increase in the strength and stability can be considered as the lime utilization on long-term results occurring during curing and afterwards. Also, according to the reports, swelling and damages occur in the lime-stabilized soil containing sulfate. The effective role of the iron furnace slag has been well recognized in increasing the strength against sulfates and corrosive environment conditions of the mortar containing lime and sulfates.
Material and methods
Adding the slag products of the melting furnaces and lime is a method used to stabilize dispersive soils. The present study makes use of a mixture of clay featuring low plasticity with 1% and 2% lime and slag, for 0.5%, 1%, 3% and 5% of the weight, to improve dispersivity, shear strength and plasticity. The samples were kept in constant temperature and humidity for a day and then were subjected to direct shear, uniaxial strength and pinhole tests.
Results and discussion
It was observed based on pinhole experiment of the initial dispersive soil sample, denoted as D1, that the sample, shown by ND2, containing lime, for 2% of the weight, and slag, for 5% of the weight, turned out to have become non-divergent. The results of the direct shear test showed that the adhesion coefficient of the slag-free samples stabilized using 1% lime has been increased from 0.238 kg/cm² to, respectively, 0.251 kg/cm², 0.373 kg/cm², 0.41 kg/cm² and 0.48 kg/cm²  per every 0.5%, 1%, 3% and 5% slag added. The adhesion of the samples stabilized using 2% lime as determined in the direct shear experiment were 0.615 kg/cm², 0.671 kg/cm², 0.724kg/cm² and 0.757kg/cm² per every 0.5%, 1%, 3% and 5% slag added. Also, the internal friction angle of the samples stabilized using 1% lime was found an increase from 14.3° for slag-free samples to 18.11°, 21.3°, 21.86° and 21.92° per every 0.5%, 1%, 3% and 5% added slag. As for the samples stabilized using 2% lime, the internal friction angles were found in direct shear test equal to 23.15°, 23.53°, 23.76° and 24.12° per every 0.5%, 1%, 3% and 5% slag added. The uniaxial strength of the slag-free samples stabilized using 1% lime was found an increase  from 1.0014 kg/cm² to, respectively, 1.0616 kg/cm², 1.0782 kg/cm², 1.2127 kg/cm² and 1.2246 kg/cm² per every 0.5%, 1%, 3% and 5% slag added. The uniaxial strength rates has been determined in the direct shear test of the samples stabilized using 2% lime were 1.1367 kg/cm², 1.1885 kg/cm², 1.2322 kg/cm² and 1.2872 kg/cm² per every 0.5%, 1%, 3% and 5% slag added. The amount of axial strain of the slag free samples stabilized using 1% lime was found decreased from 9.6842% to, respectively, 9.3333%, 9.2683%, 9.6364% and 8.4444% per every 0.5%, 1%, 3% and 5% slag added. Moreover, the axial strain amounts obtained for the samples stabilized using 2% lime were 7.7333 kg/cm², 7.6316 kg/cm², 7.1517 kg/cm² and 4.7619 kg/cm² per every 0.5%, 1%, 3% and 5% slag added.
The study results indicate that slag and lime have the capacity of improving the studied soil’s dispersivity. Furthermore, it was figured out that adding slag to the soil causes an increase in the soil strength and improves the shear strength parameters. It can be stated according to the observed results that the use of slag, a byproduct of iron smelting industry, as a substitute for a given percentage of lime is effective on the reduction of the clay soil’s divergence potential. The results of the experiments carried out to determine Atterberg limits are suggestive of the idea that the increase in the slag and lime fractions brings about a decrease in the liquid limit and plasticity and improves the plasticity properties of the soil. The reason why the soil plasticity has been reduced after being mixed with lime and slag is the cationic exchange and coarsening of the soil texture. Addition of lime to the soil causes an increase in the plasticity limit and a reduction in the liquid limit. Therefore, the plasticity index is decreased and the plasticity characteristics of the soil are improved. Adding 1% lime to the dispersive soil leads to small reduction of the liquid limit from 32.43% to 31.73%, a small increase in the plasticity limit from 13.42% to 14.66% and a insignificant decrease in the plasticity index from 19.01% to 17.07%.

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Introduction
The discussion of modeling the interaction of soil-pile groups due to a large number of parameters involved in is one of the complex topics and it has been one of the interests to researchers in recent years and has been dealt with in various ways. In recent years, the artificial neural network method has been used in many issues related to geotechnical engineering, including issues related to piles.. In this study, firstly it was tried to explain the importance of soil - structure interaction in calculating the dynamic response of bridges. Then, the effect of different effective parameters in calculating the interaction stiffness of the pile - soil group using artificial neural network was studied.  For this purpose, firstly, Sadr Bridge ( The intersection of Modarress and Kaveh Boulevard because the presence of tallest piers ) in the transverse direction, considering and without considering of the effect of soil - structure interaction was analyzed. The analysis was carried out in which the substructure soil was replaced with a set of springs and dashpots along the piles. Considering the fact that many factors are involved in determining the equivalent stiffness of springs, in the second stage, the effect of different factors on the stiffness of spring equations using artificial neural network was investigated. Finally, the artificial neural network method was used as a suitable method in order to estimate the equivalent stiffness values, the equivalent stiffness of the pile - soil group was introduced for different input values. equivalent stiffness of the substructure soil using the artificial neural network ,has not been used by researchers yet, so estimation of the optimal length and diameter of piles used in constructions and estimating the seismic performance of the bridge system after its implementation could be effective .
Material and methods
In this paper, spring-dashpot method is proposed to the non-uniform analysis of single-pier bridges which led to a 5-degree freedom model in the case of Sadr Bridge. This study also endeavors to investigate the SSI effect in dynamic analysis of bridges. This method is based on the traditional spring-dashpot method but in this method, non-linear stiffness is used along the piles, instead of linear stiffness and upgraded shape functions and coefficients are applied to make more precise mass, stiffness and damping matrices. Then the seismic responses of Sadr Bridge are compared in different conditions including or excluding the SSI effects. Considering the fact that in the present study to calculate the stiffness of the soil-pile group at depth, due to the effect of soil - structure interaction, the recommended method by API is used, the study of neural network analysis was used and the effect of different parameters used to determine the complexity of the soil-pile group system has been evaluated. The multi-layer feeder network, which has the most application in engineering issues, has an input layer, an output layer and one or more layers of hidden content, has been used for this purpose.  The best model of the neural network with a topology of 1-20-6 was provided using the hyperbolic sigmoid activation function, and the Levenberg Marquardt model and the training cycle 84, which had the least error mean square and the best regression coefficient. The effect of internal friction angle, soil density, pile diameter and the resistance per unit length has been evaluated with this method.
Results and discussion
[8] ارائه شده است صورت می پذیرد In this study, the importance of considering the effect of soil - structure interaction on the dynamic response of the Sadr Bridge was studied. Dynamic stiffness of the soil around the pile group was calculated based on the equivalent linear method and using the p-y springs. So, the effect of substructure soil was considered in dynamic analysis of the system . The artificial neural network was used to predict the stiffness of the soil - pile group, based on various input parameters and the stiffness sensitivity analysis of the calculated output values was conducted. In hard soils, the stiffness of the pile - soil group increases with increasing the diameter of the pile in the range of 1 to 1.5 m in diameter. However, in the range of 0.5 to 1 m in diameter, the diameter of the pile does not have much effect on the stiffness of the system and also stiffness decreases in the range of 1.5 to 2 m in diameter by increasing the pile diameter. Soil specific weight and angle of internal friction can change the system stiffness but the effect of the soil specific density is much greater on the stiffness of the soil-pile group system. Generally, the specific density in the range of 1000 to 2300 (kg/m³) will increase the stiffness of the system. In general, the ultimate strength of the soil among 100 to 550 (kN/m) affects the system stiffness. This effect within the ultimate strength between 100 and 220 (kN/m) causes increasing in the interaction stiffness value of the system and in the range of 220 to 550 (kN/m) causes reducing the stiffness of the system . The ultimate strength values ​​in a unit of length outside of the above range have little effect on the system interference stiffness. Despite the fact that the problem of calculating the soil - pile interaction stiffness is a direct solution, the use of the proposed neural network model can help in predicting optimal values ​​of diameter and length of the pile to achieve maximum soil- pile stiffness and especially for long bridges it will has a significant impact on reducing cost and seismic design of the bridge.
Conclusion
The results of this study are as follows:
The results showed that considering the interaction effect, although it increases the relative displacement of the deck, reduces the maximum base shear and moment. This suggests that considering the maximum base shear and moment in the interaction conditions may not lead to a seismic design for certainty, although closer to reality.
Artificial neural network is an efficient way and new method to predict the stiffness of the soil-pile group system based on different input values that have not been used yet. So that with the physical and mechanical properties of the soil as well as the geometric properties of the piles, it is possible to predict the interaction stiffness values with the proper precision.
According to the results and diagrams obtained from the neural network model, which are mainly sinusoidal, the optimal values ​​of the interaction stiffness can be obtained by obtaining the pile diameter, specific gravity, the internal soil friction soil to achieve optimal interaction strength. It is also possible for each site to estimate the depth of the piles in order to achieve optimal hardness. 
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Introduction
Expansive soils are a very common cause of extreme damages because they are susceptible to volume change due to a change in water content. Geotechnical problems associated with the expansive soils are well documented in different literature. As a result, a clear understanding of the behavior of such soils is required for the effective design of structures and infrastructures on these soils. The effects of hydrocarbon pollutants as a flooding fluid on the swelling potential of an expansive soil during wetting and drying cycles have not been considered in the previous researches. The aim of this research is to study the properties of an expansive soil with different flooding fluids, i.e. distilled water and solutions of glycerol with 10 and 20% through a number of cycles of wetting and drying tests under constant surcharge pressure.
Material and methods
The soil that was used in this work was a highly expansive clay soil (according to the classification by McKeen (1992)). It was prepared by mixing 20% bentonite and 80% kaolin. This soil was classified as a clay with high plasticity according to the Unified Soil Classification System (USCS). The optimum water content in the standard compaction test was 18.11% and the maximum dry unit weight was 16.27 kN/m³.
Distilled water and solutions of glycerol with concentrations of 10 and 20% were used for flooding the samples. To prepare the glycerol solutions, the required amount of glycerol was mixed with distilled water.
For making compacted samples for testing, the needed air-dried soil was weighed and the required water was added to it to reach the desired water content (4% below the optimum water content according to the compaction curve). The soil and water were mixed by hand and then was kept in a plastic bag for 24 hours to allow the uniform distribution of moisture in the soil. Samples were prepared by static compaction of the moist soil in a special mould.
A conventional oedometer was modified to allow the wetting and drying tests to be conducted under controlled surcharge pressure and temperature. During wetting and drying, the vertical deformation of the sample was measured by using a dial gauge. The variation of water content with void ratio during wetting and drying cycles was determined by using the information from the duplicated samples.
Results and discussion
Fig. 1 shows the variations of vertical deformation during wetting and drying cycles for samples that were flooded with distilled water and solutions of 10 and 20% glycerol. This figure illustrates that by increasing the number of cycles the amount of irreversible deformation is reduced until the equilibrium condition is achieved where the deformation due to wetting and drying is nearly the same. These results indicate that by increasing the concentration of glycerol the equilibrium condition with reversible deformation is reached in a fewer cycle of wetting and drying than the sample that was flooded with distilled water.

Figure 1. Wetting and drying cycles for different quality of flooding fluids
The results of void ratio versus water content at the equilibrium conditions for the samples flooded with distilled water and solutions of 10 and 20% glycerol (that were obtained from duplicated samples) are shown in Fig. 2. This figure displays that the paths of drying-wetting for different flooding fluids are nearly S-shaped curves. It is also seen in this figure that the order of the curves in this space is dependent on the percent of glycerol, the curves for the sample flooded with distilled water and 20% glycerol are located at the top and bottom of the space of void ratio against water content.

Figure 2. Water content-void ratio paths for different quality of flooding fluids
The change in the thickness of the diffuse double layer (DDL) affects on the swelling behavior of soil. The thickness of DDL is dependent on factors such as valency and concentration of cations, temperature, and dielectric constant. The value of dielectric constant for water is 80 and for solutions of 10 and 20% glycerol are 74.9 and 71.8, respectively. The magnitude of the attractive and repulsive forces between clay particles are inversely and directly depended on the value of the dielectric constant. The reduction in the value of the dielectric constant causes an increase in the attractive forces and leads to a reduction in the thickness of DDL. When the flooding fluid is a solution of glycerol, the initial chemical composition of pore fluid in the sample is changed. The chemical composition of pore fluid has different effects on the structure of clay soil such as changes in the thickness of DDL. When the flooding fluid is distilled water the pore fluid of samples has a dielectric constant of about 80. Therefore, the values of attractive and repulsive forces are not changed because of the same dielectric constant of flooding fluid and pore fluid. The results of tests on these samples (flooded with distilled water) show that by repeating the wetting and drying cycles the potential of swelling is reduced and after several cycles a reversible equilibrium condition is attained as depicted in Fig.1. When the pore fluid is the solution of glycerol, the attractive forces are increased due to the reduction of the dielectric constant of pore fluid and causes a reduction in the thickness of DDL. The shrinking of DDL is led to the formation of flocculated structure in the soil and results in pasting of particles together leading to the reduction potential of swelling. When the concentration solution of glycerol is increased the dielectric constant is decreased, the magnitude of attractive forces is increased and the degree of flocculation of the soil structure is increased that is yielded to a reduction of swelling potential.
Conclusion
Effect of different flooding fluids on the properties of an expansive soil during wetting and drying cycles were studied. The following conclusions can be drawn from the present research:
-After a number of wetting and drying cycles, the observed irreversible          deformation was diminished and equilibrium was achieved. The solution of glycerol causes more reduction in the potential of swelling than distilled water.
-The wetting and drying paths in the space of void ratio and water content are S-shaped curves. The variations in the void ratio of samples flooded with the solution of glycerol are smaller than distilled water../files/site1/files/142/babaei.pdf
 
 

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Introduction
Improving the geotechnical characteristics of soils including superficial or deep soils has always been a challenge to geotechnical engineers. Therefore, various physical and chemical methods are used to improve different types of soils. In general, any physical, chemical, biological or combination of methods are used to change the characteristics of natural soil mass in order to achieve engineering goals which is defined in the "soil stabilization." Among different types of additives for soil stabilization, the use of pozzolans has been investigated by researchers because of their chemical compatibility with the environment and the cementation products due to chemical reactions. Todays, a lot of researches has been done on the use of natural or artificial zeolites as pozzolanic materials for the production of cement mixtures. This material, as a pozzolan, increases the speed of the pozzolanic reactions and reduces the density of cement products. However, many studies have been done to investigate the effect of zeolite and sepiolite on the resistance of cement products such as concrete, but so far, the use of these additives has been less considered for soil improvement. On the other hand, because of the compatibility of zeolite and sepiolite with the environment and their unique physiochemical properties, it is necessary to pay attention to these additives in order to improve the soil. Therefore, in this research, the effect of zeolite and sepillot additives with different percentages at different treatment times have been investigated to determine the elasticity modulus and hydraulic conductivity with focus on soil microstructure behavior.
Materials and methods
1. The properties of the soils
In this research, two types of soil including clayey sand (with 20% clay) and sandy clay (with 51% of clay) were used. The studied soils were a mixture of clay and sand of Firoozkouh (a typical type of sand located in north of Iran). Some physiochemical properties of zeolite and sepiolite are presented in Table 1.
Table 1. Physiochemical properties of zeolite and sepiolite used in this study

L.O.I.	Na2O	K2O	MgO	CaO	Fe2O3	Al2O3	SiO2		Chemical component
25.11	0.02	0.01	15.73	0.01	o.61	0.3	55.3		Sepiolite (%)S
11.94	0.13	-	0.87	2.45	1.26	13.54	69.74		Zeolite (%)

2. Experiments
The uniaxial compressive strength tests were performed at 0.1 mm/min according to ASTM D2166 standard. The stabilized soil samples were compacted at percentages of 0, 5, 10, 15, 20 and 25 in cylindrical molds (38mm × 76mm) in five layers to achieve the desired density. In order to investigate the effect of curing time, the samples were placed inside sealed containers and underwent the test at instantaneous, 7, 14, and 28 days and at the desired additive percentages. To investigate the effect of additives on the soil hydraulic conductivity, clayey sand soil with additives 5, 10, 15, 20, and 25% was prepared using dry mixing method. Then, the prepared mixture was poured from a specific height into the permeability mold with a height of 8.65 cm and diameter of 5 cm. In this way, the specific dry unit weight of all samples was obtained as 1.47 g/cm³, close to the minimum specific dry unit weight. In this research, concerning the considerable effect of fine-grained soils on hydraulic conductivity, falling head test was used to determine the permeability coefficient.
In order to the morphology of the clayey sand soil without additives and stabilized with additives 15% was examined through SEM test.
Discussion and results
1. Modulus of elasticity
In this study, after uniaxial tests in different percentages and ages, the stress-strain graphs were plotted and then the elasticity modulus was calculated. The results showed that, with increasing zeolite content, the modulus of elasticity has been increased and, with increasing curing time, except for a slight decrease, after 7 days, the modulus of elasticity increased. During the initial treatment (7 days), the hardness of the sandy clay soil decreased and then increased with increasing time. In general, hardness in both soils in the high percentages of zeolite is significantly is increased.
Also, the effect of sepiolite on the modulus of elasticity has been studied. The results indicate that with the increase in the percentage of additive and lengthening the curing time, the modulus of elasticity is increased. This increase in the stabilization of both sandy clay and clayey sand soil is almost the same. In addition, in the case of sepiolite modification, the elasticity of sandy clay and clayey sand is approximately equal to 5 times in comparison to the initial value of unstabilized soil. However, in zeolite, the modulus of elasticity in clayey sand soils is almost 2 times, and sandy clay is nearly 5 times higher.
2. Permeability
To investigate the effect of additives on the soil hydraulic conductivity, clayey sand soil with additives 5, 10, 15, 20, and 25% was prepared using dry mixing method. The samples were saturated in a short period and permeability test was carried out immediately. Permeability coefficient changes were mostly influenced by physical factors. Therefore, due to the fineness of both types of additives, the hydraulic conductivity decreases with increasing additive content. The amount of reduced hydraulic conductivity in sepiolite stabilization is greater than zeolite due to the structure of the sepiolite (fiber-shaped) compared to zeolite.
 
 
3. SEM imaging
In this study, attempts were made to examine the reasons behind the obtained results more carefully through SEM imaging.

c                                     b                              a
Figure 1. SEM image of non-stabilized clayey sand soil (a) soil stabilized with zeolite 15% (b) soil stabilized with sepiolite 15% (c) during the curing time of 28 days at magnifications 10000X
Figure 1a displays the SEM image of non-stabilized clayey sand soil. As can be seen in the figure, the soil structure is clear as layered and clay scales can be seen as laminated. Figure 1b demonstrates the SEM images of clayey sand soil stabilized with zeolite 15% during the curing time of 28 days. The sample has lost its layered structure in response to stabilization with zeolite during the curing time and changed into an integrated structure. This can be due to incidence of chemical reactions such as ion exchange and pozzolanic reactions in response to adding zeolite. Figure 1c demonstrates the SEM images of clayey sand soil stabilized with sepiolite 15% during the curing time of 28 days. As shown in the figure, the sepiolite has a fibrous-shaped structure that is longitudinally twisted. Also, with  curing time increase, complex structures have emerged that could be due to the occurrence of chemical reactions.
Conclusion
This study examined the effect of zeolite and sepiolite additives on strength parameter of clayey soils. Accordingly, uniaxial compressive strength test was performed on clayey sand and sandy clay soil at percentages of 0, 5, 10, 15, 20 and 25% of zeolite and sepiolite with instantaneous curing times of 7, 14 and 28 days. Further, permeability test was conducted at different percentages on stabilized clayey sand soil. Also, to investigate the effect of these materials on soil microstructure, SEM imaging was performed at 28 days. The results show that both additives increase the elastic modulus of clayey sand and sandy clay soils. Also, the results indicate a steady increase in the stiffness of the cured soil with sepiolite during processing time. However, reducing soil hardness can be seen in stabilizing with zeolite at lower rates and lower percentages. In permeability test, hydraulic conductivity decreases with increasing additive content. The rate of permeability reduction in sepiolite is higher than zeolite. SEM images show that chemical reactions create an integrated structure that ultimately increases uniaxial compressive strength and modulus of elasticity. Also, SEM imaging depicts physical changes along chemical reaction in soil stabilized with sepiolite. Ultimately, increasing soil strength resulting from additive alongside environmentally friendliness is recommended in superficial and deep improvement of soil../files/site1/files/144/Rajabi.pdf
 

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Introduction
The existence of problematic soils due to their geotechnical properties, such as low strength and stability, high compressibility, and swelling, is one of the most important issues and challenges that geotechnical and civil engineers are faced in urban environments, especially in metropolises. Various methods are used to stabilize and to improve the behavior of problematical soils such as compaction, consolidation, stone columns, jet grouting, biological procedures, and additive materials including nanomaterials. Because of their high specific surface, the use of nanoparticles is very effective to increase the shear and mechanical strength parameters of soil. Mashhad city is located on alluvial deposits of Mashhad Plain. A wide area of this city, especially the central and eastern areas where the Imam Reza holy shrine is located, has been built on weak and fine-grained deposits. Considering constructing high-rise buildings such as hotels and commercial complexes in these areas, as well as the need for restructuring the urban decay, the soil improvement will be inevitable. Given the significant application of these nanoparticles, the purpose of this study is to investigate the effects of nanoclay and nanosilica on each other and to find their optimal composition as a suitable alternative for traditional materials to improve the weak and problematic soils. This not only increases the bearing capacity and strength properties but also reduces the cost and time of project implementation.
Method and Materials
To achieve a hybrid with maximum strength and bearing capacity in executable projects, laboratory tests were performed on the soil picked up from the vicinity around Razavi holy shrine in Mashhad mixed with nanoclay and nanosilica. The type of soil is classified as CL-ML based on sieve and hydrometer tests. The nanoclay used in this research is the type of montmorillonite- K10, and the nanosilica is as a powdered shape with 99% purity.
At first, nanoclay and nanosilica were mixed independently with soil in six different weight ratios (0%, 0.1%, 0.5%, 1%, 2.5%, & 5%) and (0%, 0.1%, 0.25%, 0.5%, 0.75%, & 1%). Soil mechanical and strength properties, including compressive and shear strength, settlement, plasticity index, and swelling, were studied by standard laboratory tests on all specimens. After determining the optimum ratio of each nanoparticle, four hybrids consisting of nanosilica and nanoclay were made in four different combinations and then the effects of these four hybrids were investigated on the soil in the laboratory scale (Table 1).
Table 1. Composition of hybrids made with different percentages of nanomaterials

Nanomaterials composition	Hybrid Name
5% Nanoclay + 0.25% Nanosilica	5NC + 0.25NS
5% Nanoclay  1% Nanosilica	5NC + 1NS
2.5% Nanoclay + 0.25% Nanosilica	2.5NC + 0.25NS
2.5% Nanoclay + 1% Nanosilica	2.5NC + 1NS

Conclusion
The results of the Atterberg limit test on improved and pure soil indicate that the addition of nanoclay and nanosilica and the optimized ratios of these nanoparticles hybrid to increase the soil resistance parameters did not change the soil swelling index.
Evaluation of shear strength test results showed a significant synergistic effect of these nanoparticles on increasing the shear strength parameters. The nanoparticles hybrid of 2.5% nanosilica and 1% nanosilica increased the cohesion up to 106% and also hybrids of 5% nanosilica and 1% nanosilica increased the internal friction angle of soil up to 32%.
Examination of unconfined compressive strength tests presented a 134% increase in the compressive strength of the specimen improved with 2.5% nanoclay and a 620% increase in soil improved with 1% nanosilica. The optimum hybrid compositions of 5% nanoclay and 1% nanosilica increased significantly the compressive strength of the studied soil up to 785% and reduced the settlement of the soil by 60% compared to pure soil.

1. Laboratory studies of electron microscopy examination on ​​pure and improved soil samples with nanoparticle hybrid revealed the presence of these particles in pores of the improved soil. On the other hand, the high specific surface area of ​​the nanoparticles increased the interaction of the soil particles, and the effect of adding these nanoparticles on the refining process is observed in compressive strength increase.

As the nanoclay, nanosilica, and hybrid of nanoparticles are the results of soil processing, these particles are very effective to solve the environmental problems because of good compatibility with soil environments. In addition, low volumes of nanoclay, nanosilica, and hybrid in these nanoparticles are necessary to increase the compressive strength and decrease the settlement of soil. Therefore, using these nanoparticles at the project site reduces significantly the cost and execution time of the project.
 
 

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We collected soil samples at 23 sites from the petroleum contaminated soils (PC) in the west of Kermanshah province to investigate the sources and ecological risk of polycyclic aromatic hydrocarbons (PAHs). In this study, source apportionment has been carried out using Positive Matrix Factorization (PMF).The total PAHs concentration, have a mean value of 92.79 mg/kg, ranging from 7.37 to 609.67 mg/kg in PC soil samples. The average abundance order of different PAH ring compounds are 3 rings > 5+6 rings > 4 rings> 2 rings. The ecological risk assessment of PAHs revealed that all of the PAHs levels were higher contents than the effects range low (ERL) value and show higher concentrations than the ERM values, except for Pyr, Chr, BaA, BbF, BkF and BaP in the soil samples. The result of benzo (a) pyrene equation (BaP_eq) values indicates that the carcinogenic potency of PAHs should be given more attention due to the impending environmental risk in the study areas. Based on the PMF analysis four sources of PAHs are identified including coal combustion (21.48%), vehicular source (13.74%), unburned petroleum (20.84%) and creosotes (43.92%).Therefore, it was concluded that petroleum activities were major sources of PAHs in west of Kermanshah province.

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The present work is conducted to investigate the effect of texture and carbonate content on internal friction angle of carbonate soils. Carbonate soils are majorly found in the bed of shallow waters and also offshores in tropical regions. Recently there is a huge construction projects including oil and gas extraction platform and facilities, harbors, refineries, huge bridges and other big construction projects in many offshore and onshore areas around the world. One of these area is located on southern part of Iran. We collected soil samples from different parts of northern coasts of Persian Gulf, then the following experiments were performed, carbonate content, three-dimensional grain size, angularity, relative density & direct shear. The results showed that the average of internal friction angle of carbonate soil is higher respect to known silicate sands. This angle is affected by effective grain size, grain angularity, and calcium carbonate content. Based on the experimental results of this study, one of the results was that the internal friction angle of carbonate soils decreases as their effective size of soil aggregates increases.
 

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This paper investigates response of triangular shell strip footings situated on the sandy slope. A series of reduced-scale plate load tests were conducted to cover different parameters including three shell footing types with different apex angles in addition to a flat footing, four different distances for strip footings from the crest of the slope namely “edge distance” and reinforcement status (unreinforced and geotextile-reinforced statuses). Bearing capacity of shell footings adjacent to crest of the slope, bearing capacity ratio, shell efficiency factor, influence of apex angle on settlement of footings and the mechanism of slope failure are discussed and evaluated. Also, empirical equations for determination of the maximum bearing capacity of triangular shell strip footings are suggested. As a whole, it has been observed that decrease of shell’s apex angle as good as increase of edge distance could significantly improve the bearing capacity. However, as the edge distance increases, the effect of apex angle on the bearing capacity got decreased. Also, it was found out that the beneficial effect of reinforcement on the bearing capacity decreased with increase of the edge distance. Furthermore, the efficiency of shell footings on bearing capacity was attenuated in reinforced slopes compared to the unreinforced status.

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The use of piles, helical anchors and, in general, helical foundations has considerably increased in the last 30 years. The adoption of this technology in the international and domestic codes of each country, as well as in research and studies, and, finally, the publication of numerous books and papers in this area, and the existence of manufacturers’ products, committees, and contractors of this technology has contributed to its expansion and development. However, such methods have progressed at a very slow pace in many countries, especially in developing countries. This paper attempts to assess the global advancement of the helical foundations by reviewing 292 papers from 1990 to 2020 and comparing the related research findings. This will help clarify the issue and determine the scope of technological progress. On the other hand, collecting valuable papers in this area will make it easier for researchers to make further research. Subsequently, the characteristics of this technology are highlighted and the reasons for its lack of progress in the developing countries are addressed. For this purpose, a questionnaire is sent to researchers, developers, designers, and contractors of the geotechnical projects. The purpose of this questionnaire is to specify the type of existing projects, the soil type of project site, the degree of familiarity with the helical foundation technology, the reasons for not using this method and the solutions available to expand and develop this method. Finally, there are suggestions to develop this approach and the issues that need further research.

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The soil of the Arvand free zone in the north of Khorramshahr is fine cohesive and cannot be used in earth works. On the other hand, suitable materials for this purpose (coarse-grained soils) are located at the farther distances which a considerable cost requires. In this regard, it is trying to improve the soil with lime and furnace steel slag. This study is focused on improvement of the fine-grained soil by adding various contents of lime and furnace steel slag. For this purpose, after sampling and performance of compaction tests, different amounts of slag (10, 20 and 30% by weight of dry soil) and lime (2, 4 and 6% by weight of dry soil) were added to the soil and after curing for 28 days, the effect of additives on the physical and mechanical properties of soil was investigated by using several tests such as Atterberg limits, compaction, uniaxial compressive strength (UCS) and CBR as soaked and unsoaked. Based on USCS classification the study soil is CL, its plasticity index is about 25% and sulphate ion content is more than 0.5%. Experimental results show that by adding slag and lime at different contents to soil, mechanical properties of soil improve dramatically, so plastic index of soil decreased and UCS and CBR has been increased. Also, the maximum dry unit weight of soil increases and the optimum moisture content decreases. The test results also indicate that the effect of lime on soil is higher than slag and the effect of slag for less than 35% is not considerable, however the test result of unsoaked CBR show that the bearing of soil increase in the more than slag content 20% is significant. According to the previous studies, due to the relatively high sulphate ion content in the soil, the use of lime alone is inappropriate and the slag can only physically improve soil conditions but also chemically prevent the formation of large volume minerals (like Ettringite) by the reaction of lime with soil sulphate ion../files/site1/files/152/%D8%AD%D8%B3%DB%8C%D9%86_%D8%B2%D8%A7%D8%AF%D9%87.pdf

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Expansive soils contain clay minerals such as compacted kaolin which are widespread in nature. Displacements of this type of soils are associated with matric suction and degree of saturation. To determine the in-situ characteristics, necessary measures may be required to deal with the possible failure related to this type of soil. Different constitutive models of unsaturated soils have been considered the subject of many recent researchers (Sheng et al. 2004; Wheeler et al. 2003; Nuth and Laloui 2008; Zhang and Lytton 2009 a, b 2012). However, those constitutive models are generally complicated that are not properly implemented in computer programs for practical applications. The Barcelona Basic Model (BBM) is one of the geomechanical constitutive models to capture the elastoplastic behavior of unsaturated soils../files/site1/files/152/%D8%B5%D8%A7%D8%AF%D9%82_%D8%A2%D8%A8%D8%A7%D8%AF%DB%8C.pdf

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In coastal industrial areas, in addition to the presence of loose soil, sulfate attack on soil improvement elements, such as soil-cement, is a double problem. Generally, the use of type V cement is recommended as one of the methods to reduce the detrimental effects. Considering the limited resources of this type of cement, firstly to determin the relationship between the cement content and the strength obtained in sulfated environments is one of the important engineering question in this field and secondly, as an alternative option, the use of type II cement which is more available, is suggested to use in combination with suitable additives. The present study pursues the above two goals by making cylindrical soil-cement specimens with sand, water and Portland sulfate resistant cements. Sodium sulfate is used as the sulfate in soil and water. In the research, first of all, the relation between type V cement content and unconfined compressive strength of soil-cement is obtained at 0% to 5% sulfate concentration, which results in a cement content of 400 kg/m³ completely limited the sulfate attack effects in a sulfate concentration of 2%. Secondly, the combination of type II cement with barium chloride and hydroxide was tested. The related results show that the combination of type II cement with barium chloride and hydroxide had higher strengths, about 2.7 to 3.3 times, respectively (in 362 days), than the soil-cement containing type V cement../files/site1/files/152/%D8%A2%D8%AA%D8%B4_%D8%A8%D9%86%D8%AF.pdf