Journal of Engineering Geology

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Tunneling in complex geological and geotechnical conditions is often inevitable, especially in urban areas. The stability analysis and the assessment of ground surface settlement of a shield tunneling are of major importance in real shield tunneling projects. The objective of this research is to determine the collapse pressure of a shallow circular tunnel driven by a Tunnel Boring Machine (TBM) of the Earth Pressure Balance (EPB) type.  In this study, analytical methods and three-dimensional numerical modeling with ABAQUS software were implemented to examine the effect of face pressure on the behavior of the tunnel. The parameters were calculated using data from Karaj subway-line 2 as a case study. The analytical method used in this study is Leca-Dormiex which is based on limit analysis theory.  The method is based on a translational multiblock failure mechanism.  Also, elastic and Mohr-Coulomb constitutive model have been used for soil behavior. The results of analytical method and numerical modeling were then compared. Based on the obtained results, face pressure assessed from the analytical method of Leca-Dormiex (upper bound) is the minimum pressure that can be implemented on the face tunnel. It also indicates that with implementation of suggested pressure of analytical method, Karaj subway face tunnel is stable and consequently execution of pre-consolidation methods in this section of the tunnel does not seem to be necessary

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Determination of stress in earthfill dams is one of the most important parameters in dam safety studies. Stress monitoring can be done using total pressure cells which are typically installed during construction. The cell is installed with its sensitive surface in direct contact with the soil to measure total stress of soil and in combination with piezometers to measure pore-water pressure acting in the soil mass. Total pressure cells needs to be installed with care to get reasonable measurements. However, measurements are often incompatible with the theoretical predictions such that pressure cell results usually have some inaccuracies. There are several parameters effecting pressure cell errors. However, in the present paper it is only focused on the height of embankment and the duration of dam construction. For this purpose, a case study, namely Alborz embankment dam located in northern part of Iran was studied. It is an earth dam with clay core with a height of 78 m. Using the monitoring data and considering the effect of embankment height and construction period parameters, a model is presented to predict the pressure cells error with Gene Expression Programming (GEP) procedure by GeneXProTools 4.0 software. The computed coefficient of correlation (R²) for the proposed model is 0.98 showing a good agreement with the monitoring data. The obtained results indicate that the ratio of height difference to time difference for Alborz dam has a significant role in dam pressure cells errors

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Subsurface flow contributes considerably to river flow and plays an important role in river sediment loads. This research has been focused on investigation of soil properties and bankstream slope on seepage erosion. For this purpose a series of lysimeter experiments were performed for four different slopes of bankstream by varying the soil grain sizes. The obtained results indicate that Reynolds number in porous medium plays an effective role in depth of scour hole in noncohesive layer. It was observed that the time of beginning of sediment motion decreases with an increase in the soil grain size.

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Introduction
Pressure tunnels in hydroelectric plants are used to convey water to powerhouses. These tunnels are the sources of seepage flow to the rock formation, thus, during the water filling, they will have a low resistance to seepage and, by increasing the internal water pressure of the tunnel, the inflow force will be transferred to the rock mass. In these conditions, the cracks, pores and all other elements of the rock mass are affected by the seepage forces in all directions. This hydro-mechanical interaction affects changing the stresses and displacements of the rock mass around the tunnel and causes modifications in the permeability of rock elements during the water filling. Therefore, changes in stress distribution lead to alterations in the permeability coefficient and redistribution of the seepage field. In these conditions, since the analytical solution of the problem is not possible, the numerical analysis based on the finite element method has been used in this study.
Material and methods
In this approach, the rock mass is considered as an equivalent continuum in which the effects of discontinuities are taken into account in its material behavior. High-pressure tunnels under internal water pressure requires reinforced concrete lining to prevent hydro-fracturing. The ABAQUS software is capable of analyzing such as seepage from the tunnel, modeling of the steel bars in concrete, and taking into account hydro-mechanical interaction. Thus, the software is used for numerical analysis.
The pressure tunnel of the Gotvand dam and hydroelectric power plant (HPP) scheme is taken as a case study for the numerical simulation. Pressure tunnel of the Gotvand dam located in the southwest of Iran is taken as a case study for the numerical simulation. Among behavioral models in the software, Mohr-Coulomb failure criterion is considered to describe the rock mass, but the principle of effective stress determines the rock mass behavior. Since the concrete lining of the pressure tunnel will undergo two mechanisms of the cracking due to tension and the crushing due to compression, concrete damaged plasticity model is used to predict the response of the concrete elements. The evolution of the yield surface of the concrete lining is also controlled with tensile and compressive equivalent plastic strains, correspondingly.
In this study, the hydro-mechanical interaction is implemented based on the analysis of the pore fluid/deformation analysis, and the direct-coupled method is used to solve the governing equations of the problem. To verify the proposed model, the elastic behavior of the media is simulated to compare the numerical and the analytical solutions and good agreement is obtained. The numerical analyses are carried out the hydro-mechanical interaction with constant permeability coefficient. When cracks develop in the concrete lining at high water pressure, the properties of the concrete lining change and as a result, the stress dependent permeability of the lining and surrounding rock mass in pressure tunnels should be considered. The coefficient of permeability controls the rate of seepage flow in porous and fractured media. Although permeability represents an original property of the porous media, it can be modified when subjected to the stress variations. Instead of changing aperture, the change in the void space or volume is the typical consequence that results to change the permeability coefficient. In order to bring the model closer to the real conditions and in the validation of the new model, the influence of the permeability coefficient variations of the concrete and rock mass on the deformations and stresses of the model has been added to nonlinear analysis by USDFLD code. Increasing the water head in the tunnel during water filling is also considered with the combination of DLOAD and DISP codes in the model.
Results and discussion
Since the lining and rock mass have nonlinear properties and complex behavior, for verification of the model in ABAQUS software, the model is simulated with homogeneous, isotropic and elastic behavior. The results of seepage flow on the interface of the concrete lining and rock mass obtained by analytical and numerical solutions indicate that there is a ±5 % difference between them. Then, the results of the elastic behavior of the model show a good agreement with the results of analytical solutions. Therefore, this numerical model has been employed for the nonlinear analyses.
Finally, the optimal thickness of the concrete lining with the appropriate arrangement of the reinforcement in the reinforced concrete linings is utilized to minimize water losses from the tunnel based on the new model. Thus, the results of the analysis with the aim of reducing the water losses from the tunnel indicate that the suitable arrangement of the steel bars in the concrete lining leads to the distribution of micro cracks in the lining, and the reinforcement stress stays at a lower value with high internal water pressure. Based on the new numerical model, it is suggested that the lining should be designed with the thickness of 40 cm and the reinforcement with the diameter of 16 mm and the spacing of 20 cm.
 Conclusion
The results of the numerical model indicate that to control the seepage outflow from concrete-lined pressure tunnels, the thickness of the lining and the suitable arrangement of the steel bars in the concrete lining play a significant role in preventing excessive seepage from the tunnel./files/site1/files/124/3dadashi%DA%86%DA%A9%DB%8C%D8%AF%D9%87.pdf

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Aggregates are one of the high demand building materials in construction of structures and their characteristics have important effects on durability and permanence of projects. Abrasion resistance is one of the important features of aggregates that their utilization in concrete and asphalt are affected by texture and lithology of them. As rock consisted of harder minerals have higher abrasion resistance like igneous rocks, due to more siliceous minerals. More varieties in mineralogy compound usually lead to increase in aggregate abrasion. Aggregates that are contained of different minerals usually have less abrasion resistance. Porosity usually decreases the resistance abrasion. In addition to lithological properties, the environment where aggregates are deposited is important in determining resistance-related parameters of aggregates.
Rivers, alluvial fans, and taluses are the main environments where aggregates are deposited. Geological processes, such as weathering and particle movement may cause changes in natural aggregates, hence affecting their abrasion and impact resistance. Rock weathering can results in increasing porosity, producing minerals that are weaker in comparison to their original rock.
In the process of particles transport by stream water, weak parts of aggregates will be omitted. The present study is focused on the relationship between geology medium and the weight loss of aggregate in Los Angeles test. 
Methodology
Considering that lithology features in aggregates resistance against abrasion have an important role, in order to examine the effect of various geology environments in abrasion resistance of aggregates, the medium should be chosen having similar lithology. Therefore, the north of Damavand and the south of Daneh Khoshk anticline (north of Dire plain) were firstly chosen by using geology map, satellites images and field study. Damavand zone consists of trachyte and trachy-andesite volcanic rocks. These rocks cover the whole area around the Damavand peak. Also, Daneh Khoshk anticline is covered by thick Asmari formation. The selected environment are in the length of each other. Such that taluses feed alluvial fan and alluvial fans feed rivers. Samples were collected from different area of southern part of anticline. 10 river area, 12 alluvial fan and 6 taluses in the south-west area of Daneh Khoshk anticline (north of Dire plain) were chosen. Los Angeles test has been done according to standard A method ASTM D2216-10, 1990 on samples and the results were analyzed by analogous analyzer.
Results and discussion
Results show that porosity and micro-crack percentage increase, respectively in accumulated aggregate in river, alluvial fans and taluses areas. Also, porosity and micro-crack in various alluvial fans is different and is influenced by the area and length of main channel of alluvial fans’ catchment. The porosity decreases by the increase in the length of channel and area of alluvial fans’ catchment.
The percentages of aggregate weight loss in talus, alluvial fan and river areas decreases, respectively. Based on the obtained results, the lowest rates of weight loss belong to river environments (23.7 % in Daneh Khoshk and 42% in Damavand) whereas the highest rates of weight loss belong to taluses (49.3% in Daneh Khoshk and 48% in Damavand). The alluvial fans have an average state. Another noticeable point is the high weight loss in Los Angeles test in Damavand aggregate. Due to having harder mineral, igneous aggregate have more abrasion resistance, but this research illustrates that the weight loss resulting from Los Angeles test in these aggregates is high. This is because of virtues texture that weakness against the impact as well as their high porosity.
Conclusion
The result of this research indicates that the volume of aggregate weight loss in Los Angeles test is related to aggregate accumulation environment. The extent of aggregate abrasion resistance is lowest in talus medium and increases in alluvial fan and river environment, respectively. The difference in aggregate abrasion resistance in various areas result from geology process differences that applies to aggregates in various environment. The extent of caring particles in talus environment is very low and the type of movement is mass or sliding type in these media, micro-crack and weak parts remains within aggregates. The surface of micro crack is weak such that breaks easily in Los Angeles test due to the pressure results from the impact of aggregate, as well as the impact of steel ball on aggregate leading to aggregate breakages. Aggregates move more distances in alluvial fan and river. Aggregate strike together in riverbed and alluvial fan yielding to aggregates breakages from micro-cracks. As the movement distance increases, aggregates approach more to intact rock. During the particles move, the weathered and weak parts are damaged by aggregate abrasion to riverbeds and alluvial fan, and more resistant and harder aggregates remain. As the water current increases, the aggregates impact each other harder, more resistant micro-crack breakages and this change leads to decrease the weight loss in Los Angeles test.
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Slope stability could be a major concern during the construction of infrastructures. This study is focused to analyze the slope stability of Manjil landslide that was located 41+400 to 42+200 km along Qazvin-Rasht freeway, Iran. The Manjil landslide, which had 168 m long and approximately 214 m wide, was occurred due to inappropriate cutting in June 2013 and led to destructive and closure of freeway. Slope stability analysis was carried out using a finite element shear strength reduction method (FE-SRM). The PHASE^2D program was utilized in order to model the slope cutting and stability of landslide. Slope angle was flatted with 3H:2V geometry and stabilized with piling. The results indicated safety factors of 1.95 and 1.17 in the static and pseudo-static states, respectively, while the maximum bending moment with single pile (SP) in the pseudo-static state was 5.69 MN. Maximum bending moment of the pile around the slip surface was significantly large and more than the bending moment capacity of the pile. Due to the large bending moment on the pile, pile-to-pile cap connections (two pile group: 2PG) should be designed at the toe of the slope. The obtained results showed reduction of this parameter to 2.48 MN. Thus, it can be concluded that 2PG is a suitable stabilization method for the Manjil landslide.

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Introduction
The use of various additives to improve the properties of soils from past years have been studied by different researchers. Such additives are lime, cement, fly ash and fiber which have been used frequently in combination with soil. Lime is one of the oldest additives that it is utilized with different types of soils. Lime has positive impact on geotechnical properties of soil that alter some of the soil characteristics. Adding lime causes to reduce plasticity ranges, enhanced efficiency, strength and shrinkage of the soil. Extensive researches in the field of sustainability of clay with lime indicate that the optimum percentage of lime in the soil modification is between 1 to 3% by weight of the soil. But some researchers believe 8% by weight of lime are effective for soil stabilization. The presence of lime in clay soil yiels to occur some reaction, that it improves the soil properties. Reactions are included cation exchange flocculation, carbonation and pozzolanic reactions. Cation exchange between the clay cations and calcium cations takes place in lime. Cation exchange causes clay particles to get closer to each other creating complex structures in the clay soil and this improves the   clay soil features. In recent years the use of nanoparticles is considered in civil engineering field. The investigations have demonstrated that the use of nanomaterial increases cement reactivity and also improves density because it is filled with particles. Recent research has shown that the use of montmorillonite nano-clay soils to control swelling and to reduce failure potential in the soil. A number of researchers have expressed the use of nanoparticles causes to decrease the hydraulic conductivity of soils. In this paper, the effect of nano-clay and lime on the important soil parameters is evaluated. For this purpose, lime at 2 and 4 percentage and nano-clay at 0.5, 1 and 2 percentages have been added to clay soil and their impact on parameters such as optimized moisture, Atterberg limits, unconfined compressive strength and self-healing properties of soil is evaluated. Self-healing properties is one of the features, to repair damages due to internal erosion in the clay which is very efficient and important.
Materials and experimental methods
In the present research, the effect of lime and montmorillonite nano–clay to soil strength is evaluated. For this purpose, samples of clay soil (CL) has been used. In the experimental study, the percentages of additives mixed with the dry soil and then the optimum moisture and maximum specific weight of soil are determined with different percentages of additives. Soil Atterberg limits based on the ASTM D4318 standard have been determined.   Dry samples have been mixed together and then the water is added and mixed well with each other. Then the sample has been prepared in the form of a steel cylinder (cylindrical specimens) with a diameter of 50 mm and a height of 100 mm. Specimens were molded immediately and the weight and dimensions were carefully measured and then placed in plastic to prevent moisture loss and put them at 20 °c and 90%  moisture curing room.
Results and discussion
In this study, the percentage of lime is between 0, 2, 4 percent by weight and nanomaterials percentage is between 0.5 and 1 and 2 percent that can be varied in order to analyze the effect of various additives on the properties of the soil samples. The results indicate that increasing the nano-clay and lime percentage can enhance the optimum specific gravity of soil. The optimum moisture content of sample without any additive is equal to 19.5%. However, samples contain 2% nano-clay and 4% lime, the optimum moisture content increases to 23.5%. But the presence of lime reduces the maximum dry density of soil while adding nano-clay increases this amount. In samples with 4% lime and with no nano-clay, maximum dry density is 17  but in case of lime with 4% and nano-clay with 2% it is increased to 17.5 . In addition, adding lime without the presence of nano-clay only increases strength of soil. When 2 percent of lime is added, the strength of soil increases about 39 percent. As mentioned before, the effect of lime and nano-clay on increasing of unconfined compressive strength is almost the same which means by adding 2% of lime or nano-clay the strength of the soil increases about 40 percent. Using both lime and clay nanoparticles simultaneously (each 2%), a significant increase in strength of soil occurs in approximately 77 percent.
Conclusion
The use of nano-clay and lime improves soil strength parameters. But economically lime is more affordable than nano-clay. Therefore, if you need to increase only unconfined compressive strength, then the nano-clay is not recommended.
When it comes to self-healing in clay, the nano-clay can improve resistance rupture of the soil. By adding 2% of nano-clay in soil, healing of soil resistance after the break and after 24 hours can reach up to 60% of the ultimate strength of the soil. This property can be used to repair of locations that are subjected to internal erosion and scouring.
 
 

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Introduction
Landslides have an effective role in the destruction of freeways and railroads, which have been caused to many human and financial losses. Understanding this phenomenon and its effective factors can be important in planning for development projects and away from landslide prone areas. Based on extensive field in the Qazvin-Rasht freeway that the authors carried out in various researches in 2014-2017, it was found that the freeway was threatened by the type of instabilities due to variety of lithologies  and tectonic structures exploitation phase and needs to be stabilized. The purpose of this study is to determine of the distribution of landslides in different types of lithologicalunits of the Qazvin-Rasht freewaythat shows the role of geology and differences in geotechnical characteristics and tectonic structures in the creation and distribution of landslides on the road.The role of geology on the difference in geotechnical properties and tectonic structures in the creation and distribution in the road. Geological engineering properties and appropriate stabilization methods is the other goals of this study.
Material and Methods
In the study, the locations and the type of landslides are distinguished and the information were plotted on geological map. Then by the ARC GIS 10.2 program, and the use of area density method, the percentage of landslide events in each geological formation was identified. In order to study the role of lithology (type of rock, texture, mineralogy, weathering, alteration and erosion), sampling were carried out from rocks of Karaj formation, Shemshak formation, Cretaceous orbitalolina limestone and Fajan conglomerate. Geotechnical characteristics of the samples were determined by performing laboratory tests such as dry weight, porosity, uni-axial compressive strength according to ISRM standard (1979). For determining the role of tectonic structures (number of joints, dip and dip direction, length (m), spacing (cm), filling percentage, opening (mm), roughness, weathering, water, friction angle) were performed. Then, the results obtained from relative density and frequency were matched with the geological, geotechnical characteristics and tectonic structures of each formation.
Results
In order to separate different types of landslides on various kinds of rocks, area density and frequencyof  landslides were determined by Eqs 1 and 2. Graph of frequency and area density are presented in Fig. 6 and Table 2, respectively. As can be seen in this figure and table, in Karaj formation, the percentage of rock fall, toppling, avalanche, scree slope and combined slip are the highest. In the rocks belonging to the Shemshak formation, the susceptibility of the debris flow and landslides has been increased. In Fajan conglomerates and limestones of the Ziarat and Cretaceous formations, the rockfalls is more formed.
where L_I: area density, A_L:  area of landslides in each lithological unit, A_T: area of landslides in total area.
where L_F: frequency of landslide, N_L:  number of landslides in each lithological unit, N_T: number of landslides in total area.
Conclusion
Result showed that despite significant heterogeneity in lithology, geotechnics, engineering geology and tectonic structures, there are similarities between the types and distribution of landslides. Four of the identified landslides consist of rock fall, toppling, avalanche in the resistant and medium strength rocks such as andesite, trachy-andesite and basalts of Karaj formation, Cretaceous orbitalolina limestone and Fajan conglomerate with regard to the dominant direction of the joints in relation to the slope, the shear strength of the joints and their weathering, falling and scree slope in thesiliceous zone and composite landslide in the argilite-alounite zone due to the high alteration and groundwater level and water retention by the presence of clay minerals, landslide in the sequence of loose and resistant rocks, debris flow and landslides in the soils of Shemshak formation due to the lepidoblastic texture of the slate and their high erosion potential due to the weather climate along the Manjil-Rudbar freeway../files/site1/files/151/4.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