Journal of Engineering Geology

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Introduction
Series A of coarse-grained alluvial deposits of Tehran are extended in eastern and north-eastern areas of Tehran. Analyzing and studying of these alluvial deposits from a geological point of view as well as their creation time and general characteristics such as the deposits’ mineral types, their source, and formation conditions, gives a better point of view to geotechnical engineers about exploring their characteristics as well as geotechnical aspects in underground structure design, excavations, and foundation design processes. On the other hand, in order to analyze stability, estimating the factor of safety and the seismic design of these structures, considering their location, which is in Tehran with a high seismic hazard area, the necessity of knowing the exact mechanical and dynamic properties of Tehran's alluvium is felt more than ever.
Material and methods
Due to the grain size of Tehran’s coarse-grained alluviums (series A) as well as high level of cementation of them, it is impossible (or maybe so difficult) to make undisturbed samples in order to do experiments. Such that it is excavated 23 boreholes with 30 to 140 meters depth as well as 17 test wells with 20 meters depth in an area which was extended in 10 kilometers in long which were located in Tehran’s No. 13 and No. 14 districts (as it can be seen in Figure 1). During the excavation of the entrance ramp and tunnel of eastern highway of Tehran, in-situ tests have been done in different sequences. Since it was important to investigate real behavior of these alluviums, different in-situ tests such as plate load test, in-situ shear test, pressuremeter test, and downhole test have been done as well as many laboratory and field tests. Furthermore, (1) X-Ray Diffraction (XRD) and (2) X-ray Fluorescence (XRF) as well as (3) Scanning Electron Microscopy (SEM) methods, have been used to explore the type of minerals and those used in cementation.
 
 
 
 

(ب)
 
 
 
Figure 1. a) Geological plan and the location of boreholes and test wells in the alignment of East Tehran Freeway
Results and discussion
Based on the results of XRD tests, it is quite clear that the largest weight percentages of tested samples are lime and silica.
Calcium and magnesium levels-as the high-power cations in flocculation process-in soil sample No. 1 (soil with high cementation level) are much more than soil sample No. 2 (soil with moderate cementation level).
This is the cause of high cementation level of soil sample No. 1 comparing with soils sample No. 2. A rapid increase in stress level can be seen in in-situ shear test results, in low shear displacements, up to reaching a maximum of τ_p (peak point) and afterwards reduction in shear stress with softening behavior.  
Cohesion and shear strength levels also increase by increasing the depth. According to the plate load tests results, an increase in soil modules changes can be seen in different depths by depth increasing.
Large tendencies to increase in volume and dilation can be seen in under shear load cemented soils, after applying a primary compression on them. A brittle behavior with the occurrence of a certain peak can be seen in cemented samples. The significant increase in strength is directly related to the severe dilation rate, which can be seen in cemented samples results.  The shear strength would be decreased, if this cement is broken during the particles’ displacements.
The results of downhole tests are shown in Figure 2. According to this figure, it has been explored that V_s,30 is about 600 m/s in moderate cemented soils while it is about 850 m/s in highly cemented soils.  Because of the homogeneity and uniformity of sedimentary deposits, shear wave velocity is increasing due to the higher density of the layers and high level of cementation in both of the soil types. However, this increase is not significant at depths above 25 meters.
Conclusion
Based on the results, cementation level of the eastern coarse-grain-alluvium of Tehran is moderate to high and minerals used in cementation of this type of soil are generally carbonated and especially calcite.
Investigating the level of cementation of soil as well as the results of chemical analysis and in-situ tests, it can be found that the strength and deformation parameters of the soil are directly related to the degree of its cementation.
Based on the obtained results, the deformation modulus increases by about 25%, the cohesion by about 55% and the shear wave velocity by about 30% with increasing the degree of cementation (Table 1).
Increases of these parameters are directly related to depth. However, the cementation level does not significantly affect the internal friction angle of the soil.
Table 1. Average results of in-situ shear tests

Deformation Modulus (MPa)	Peak Friction Angle (deg.)	Cohesion (kPa)	USCS	Depth (m)	Sample
50-60	39	30-35	GW-GM	5	Moderately Cemented Soil (M.C. Soil)
75-85	41	50-60	SP-SC	10
85-90	41	50-60	GW-GC	15
95-105	41	50-60	GW-GC	20
60-70	39	35-40	GW-GM	5	Highly Cemented Soil (H.C. Soil)
75-85	39	50-60	GW-GC	10
110-120	42	65-75	GW-GC	15
125-140	41	110-120	GC	20

 
 

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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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Introduction
Grouting is one of the most widely used methods of soils improvement in which pressurized grout penetrates in the voids, of the soil. In the grouting method, in addition to reducing the permeability, shear strength and stiffness of the soil increase significantly. However, application of this method in projects such as dam construction and soil improvement requires the use of a large volume of grouting materials in order to satisfy the design criteria. In more recent years, due to the economic and environmental issues, in the case of cement-based grouts, replacing the whole or a portion of Portland cement with other materials has been experimentally investigated. A special type of kaolinite clay called metakaolin has recently been used in concrete, which has yielded interesting results. However, few studies has been conducted on the use of metakaolin in cement-based grouts. Such that, its effect on the mechanical behavior of the grouted soil are not well understood. Accordingly, in the present study, the mechanical behavior of a type of sandy soil grouted with different combinations of Portland cement and metakaolin was experimentally investigated in laboratory scale.
Material and methods
Different materials used in the present study including sand, cement, metakaolin, bentonite and water were selected based on the standard criteria and with the aim of better interpreting the test  result and their differences due to considered influencing factors. Sand was obtained from Malayer Shushab river bed. According to the Unified Soil Classification System (USCS), it is classified as SP. Ordinary Portland cement was used in this study regarding to its widespread application in the practical works. The metakolin is classified as class N pozzolan according to the ASTM C618. Another constituent material of grout is bentonite which is produced by Iran Barit factory as sodium-calcium bentonite. Its liquid limit and plastic index are 296 and 262 percent, respectively. The water used to prepare the grouts was provided from Hamedan drinking water, which according to ASTM C94 has the required quality for grouting operations in laboratory.
The device for grouting specimens was developed at the Soil Mechanics Laboratory of Bu-Ali Sina University during the present study. It equipped with grouting pressure control system and tool for keeping grout in homogeneous conditions during the grouting operation into specimen. The samples were prepared with 0, 5, 10, 15, 20 and 25 percent substitution of cement with metakaolin. Curing time of grouted samples was considered as14 and 28 days.
In order to investigate the factor affecting stress-strain behavior of the grouted sand, the samples were sheared using advanced triaxial apparatus. After passing considered curing time, the samples were sheared considering three levels of confining pressures of 50, 100 and 200 kPa and by applying axial strain rate of 1 mm per minute. For each test, the maximum deviator stress and its corresponding axial strain were recorded. In addition, for studying post peak behavior of grouted soil, for every one of tests, average ratio of deviator stress to the axial strain as softening modulus, was calculated from the deviator stress-axial strain curves.  The moisture content of the samples was also measured according to ASTM D2216 at the end of tests. In the following, the role of different factors influencing stress-stain behavior of grouted sand including; confining pressure, ratio of water to the mix of cement and metakaolin, percentage of metakaolin, curing time and moisture content were investigated.
Results and discussion
Figure 1 shows the effect of metakaolin as alternative of a portion of cement on maximum confined compressive strength and its corresponding axial strain.
For the samples confined by pressure of 50 kPa the maximum confined compressive strength is almost constant by replacing cement with metakaolin up to 10%. However, the amount of axial strain corresponding to the maximum compressive strength of the specimens increases by 6% (Figure 2). For 25% replacement, the maximum confined compressive strength of the samples decreases by 17% compared to the initial state (pure cement). In contrast, the axial strain value related to peak state of most samples has been increased by 4% in comparison to the initial state.
 
In the case of confining pressure of 100 kPa, by replacing up to 10%, the mean confined compressive strength of the specimens was almost constant. However, the amount of axial strain corresponding to the peak state of the specimens has been increased by a maximum value of 18%. For 20% replacement percentage the compressive strength of the specimens has been decreased by about 15% compared to the initial state. However, in the range of 20 to 25 percent, the reduction process has slowed down, which can be due to various factors such as the effects of sample densification during further increase of metakaolin. According to Figure 1, it can be seen that in the range of 20 to 25% substitution, the amount of strain at failure state increased by an average of 40%, which indicates that the sample is more deformable.
In the case of confining stress of 200 kPa, by replacing 10% of the cement with metakaolin, maximum confined compressive strength and its corresponding axial strain, has been increased by approximately 5 and 14%, respectively. With increasing cement substitution up to 25%, the resistance of the specimens decreased by 8% compared to the result of sample grouted with pure cement. Although, axial strain at peak state has been increased by 28%. From the Figure 1, it is obvious that increasing in confining pressure yeilds a considerable increase in the maximum compressive strength of grouted soil. Besides, post peak behavior of grouted soil is also affected significantly by confining pressure. Such that an increase in confining pressure leads to decrease in softening modulus. On the other word, grouted soil displays a more deformable behavior. It should be noted that these aspects of grouted sand cannot be described by unconfined test. However compressive strength of the grouted soils in the majority of case, has been evaluated based on the unconfined test results. 
Conclusion
The aim of this study was to investigate, in laboratory scale, the mechanical behavior of sand grouted with cement-based grout and considering different percentage of metakaolin as an alternative for a portion of cement. The soil samples were grouted using a specific device developed during present study. After passing curing time the samples were sheared using triaxial apparatus by considering three levels of confining pressures. The main findings of this experimental research are as follows:
- Replacing 10% of cement with metakaolin, increases deformability of grouted soil, without reducing compressive strength. Deformability of grouted soil increases with adding more percentage of metakaolin however, in this case compressive strength decreases.
- By increasing confining pressures, more values of metakaolin can be used instead of cement in the grout.
- Increasing confining pressure, increases compressive strength, increases deformability and deceases softening modulus at post peak behavior.
- Shear strength parameters of grouted sand is affected by adding metakaolin into the grout. Increasing the percentage of metakaolin results in small changes in the internal friction angle of the grouted sand, however, the amount of cohesion decreases.

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