Journal of Engineering Geology

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The ever increasing growth and development of the metropolitan city of Karaj in recent years has placed implementation of basic studies on Alluvium of Karaj Plain on the top of significant priorities of the region’s development projects. Therefore, in the present paper, the alluvium of South Karaj was studied based on relevant numerous geotechnical laboratory and field tests. In this regard, an area from Pol-e Fardis to Serāh-e Andishe with a length of 10 km is selected and the geotechnical engineering features of this area were taken into careful consideration and study. The carried out studies divide South Karaj Alluvium into five independent parts whose engineering description are presented. On the other hand, since the results of most of relevant laboratory and field tests have been collected, some relations for calculating Elasticity Modulus, Soil Inner Friction Angle as well as other geotechnical parameters in South Karaj Alluvium are introduced. Finally, the process of soil classification in South Karaj Alluvium is compared with the same process in other regions of Karaj, and, given the soil engineering features of Southern part of South Karaj Alluvium, some suggestions are presented for optimization and facilitation of future development projects in south Karaj Alluvium. Geotechnical studies.

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Determining the precise shear strength parameters of the fine grained soils is always a difficult task. In order to conduct the shear strength tests and determine the mechanical parameters of the soil, achieving an untreated high quality sample is a problem with a high degree of importance. Therefore, during the recent decades many researchers have attempted to provide relations between strength parameters and soil physical characteristics in a specific structure and so to provide the possibility of estimating the strength parameters based on these characteristics. The aim of this research is to estimate the shear strength parameters of a wide region of fine grained alluvial soil located in southern Tehran, Iran. In this regard, the geotechnical data including physical and shear strength parameters of 294 boreholes were firstly collected from the site. Then, the obtained data were statistically and independently analyzed. Based on the results of analyzes, the soil geotechnical parameters were presented for various depths with an acceptable level of reliability. Moreover, they were considered as a basis for providing a nonlinear regression model to estimate the soil shear strength parameters and based on the index physical characteristics of the fine grained soil (water content and plasticity index). The developed model is capable to predict the soil drained shear strength parameters and also other similar soil properties with a very good accuracy

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Subsurface dams is accordant with nature structure which is useful for water resources management, especially for preventing unused underground water. Regarding to reservoir alluvium, geological and geotechnical characteristics of this type of dam is important. Therefore, in present study, characteristics of the underground reservoir alluvium in Mastbandy area (South of Ardestan-North East of Isfahan) has been investigated. In this regard physical and mechanical properties of reservoir alluvium has been determined, using in situ and laboratory tests. Test results show that the type of alluvium is mostly non uniform dense granular soils without plasticity. Also its permeability is medium to high. Due to the porosity obtained from tests and the depth of the reservoir sediments (5 to 12 meters), in the case of subsurface dam construction, its volume would be about 200000 cubic meters. In general, due to full and empty of reservoir, loading and unloading cause the settlement. Since almost reservoir sediment are gravel and sand, the settlement is mainly immediate settlement. Due to obtained mechanical parameters, the amout of immediate settlement is equal to 16 milimeter

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Soil classification is one of the major parts of geotechnical studies. So assessment of existing methods for soil classification in different areas is important. For soil classification is used in situ and laboratory test results. Sampling and identification tests are laboratory methods for soil classification. CPTu test is in situ method for soil identification and classification, due to accuracy and speed, this test is used widely in geotechnical study today. Many researchers are proposed some charts for soil classifications based on the parameters measured in CPTu test. In this paper for evaluation the performance of these methods, 58 CPTu test results have been used. These tests are related to four areas in southern Iran. The soils are classified by CPTu methods and then they are compared with 372 laboratory soil classification. Research results show the chart proposed by Robertson (1990) which based on Qt, Ft and Bq variables has the best adaptation with the laboratory soil classification in these studied areas. Then according to data obtained from research, proposed a modified charts based on Rf, qt-u0/σ΄ v , that show 90% adaptation with laboratory soil classification.

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Free vibration of soil often occurs during earthquakes. Since the vibration caused by earthquake does not have (steady state harmonic vibration) continuity, the alluvium vibrates with its natural frequency between two natural seismic waves. This study evaluates the effect of piles on the period of free vibration of a soil layer using numerical method. In the first stage, using analytical equations for calculation of vibration period of a soil layer and a column with continuous mass, the results were analyzed by the software. In the second step, piles with the same dimensions and distance were added step by step, and the vibration period for the soil layer with piles was calculated. The friction or floating effects of the piles on alluvial soil vibration period was also examined. The results show that as the number of piles increases, the differences between the results of one dimensional analysis of alluvium soil and the results of the software become different, and this creates the need for specific arrangements for seismic analysis of this kind of alluvium (with inserted piles). The results also suggest that end-bearing piles have a greater effect on alluvial soil vibration period, and with increased amount of the floating of these piles, these effects decline.

 

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In this research, the relationship and reaction between quantitative and qualitative Shahre Rye spring’s karstic water (Cheshme Ali) and spring’s adjacent alluvium aquifer have been considered to determine the relationship between alluvial and karstic aquifers and to study the connections between the two different groundwater environments. The results of the present research suggest geological conditions, hydrogeology and different hydraulic condition between Cheshme Ali karstic water with its surrounding alluvium’s aquifer. However the study results show the lack of a hydraulic connection between the two different groundwater environments (karst and alluvium) that are formed by north Rye fault.
Introduction
There have been many studies in the field of the present research, some of which are mentioned below.
(Tobarov, 1966). The N. Massei et al. (2002). (Robert E. 2005). (Ezatollah Raeisi 2008). (Cholami et al. 2008). (N. Goldscheider and C. Neukum 2010). (Dusan Polomcic et al. 2013).
The aim of this research is to identify the hydraulic relation between the alluvial aquifer and the karstic aquifer of the Cheshme Ali, during which the geographic, topographic and geologic situations and the changes in water discharge of Cheshme Ali and the changes in water table of the observation wells of the aquifer to the north of the spring have been reviewed simultaneously.
The results indicate a lack of relation between the alluvial aquifer and the karstic aquifer of the Cheshme Ali in Shahre Rye.
The general specification of the study area
The surface area of Shahre Rye equals to 2,293 km² and the city is limited to the north by Tehran, to the south by Qom, to the east by Varamin and Pakdasht and to the west by Islamshahr, Robat Karim and Zarandieh (Fig. 1). The Cheshme Ali is located in the eastern parts of the city and southeast of Tehran. From a geographic point of view, the Cheshme Ali spring is situated in the southern part of the Cheshme Ali hill, and after leaving the ground, the spring's water flows to the south of Shahre Rye.
Methodology
1. Topography
The topographic specifications of the Cheshme Ali and its surrounding are as follows:
The highest points of the Cheshme Ali's surroundings are the Sepaye Hills with an altitude of 2,085 m above the sea, which are located to the east of Cheshme Ali. The height of Bibi Shahbanoo hill to the southeast of Cheshme Ali is about 1,498 m. The altitude of the northern hill of Cheshme Ali, where the spring is located is about 1,077 m and the lower sloped land surrounding it have an altitude of 1,072 m above the sea. This means that the opening of the Cheshme Ali spring is located at 1,072 m above the sea.
2. Geology
From the geological point of view, the existing units around Cheshme Ali of Shahre Rye consist of Precambrian, Mesozoic and Cenozoic sediments and rocks as geological specifications of Cheshme Ali and its surroundings are shown in Fig. 2.
From the structural geology, and geological specifications two geological sections AB, CD Were prepared and presented in Figure 3.
The Figure 3 shows, Cheshme Ali spring appears from Cretaceous thick layered limestone (Tizkooh formation Kt1) and the shahre Rye fault mechanism on either side of layering. However the water flow of cheshme Ali is nearly east – westerly after spring’s openings (A) and then spring water flow direction is to the south (Fig. 4).
The hydrogeology of the spring and the wells
1. The Cheshme Ali in Shahre Rye is a karstic spring, with few hydrogeological specifications that are concluded from the result of geological and hydrogeological review and analysis of the spring’s water quality.                                                           
Therefore, the karstic Cheshme Ali spring has a varied range of discharge which is from medium (25 to 100%) to high (>100%). Moreover in the curves of the spring’s discharge and simultaneous rainfall, shown in figure 5, the peak volume of water discharge of the spring corresponds fully with the peak rainfall, underlining the influence of simultaneous rainfall on the spring.                
The study of the hydrographic makeup of the spring (curve 2) shows the difference in the period between the upward curve (seven and a half months) and the downward curve (four and a half months) underlining the lower permeability of the spring’s intake area versus the grounds conducting spring water to the openings.
2. The hydrogeology of the surrounding wells:
For the purpose of studying the fluctuation of water tables of the observation wells around the spring and in its adjacent alluvial aquifer, the isobaths maps of groundwater level and groundwater table of the spring’s surrounding areas were drawn ( Fig.6). The level of groundwater table to the north of spring is 5.9 m and 6.6 m to the south of it, while the spring water is at ground level. In order to have a better understanding of the potentials of groundwater table in Shahre Rye’s Cheshme Ali and its surrounding environments from south to north, the potential profile is provided in figure 7 using the potential figures of witness wells and the Cheshme Ali spring. In the potential profile, the groundwater level of the Cheshme Ali is higher than the groundwater potential level of the witness wells, which seems to suggest the recharge of the plain by the spring.
The review of the groundwater quality in wells and the Cheshme Ali spring
The groundwater quality characters of the Cheshme Ali and the wells to the north and south of the spring are presented in table 2,that shows three differences and similarities in the results of the chemical analysis of water from Cheshme Ali and from wells located to the north and the south of the spring. The difference between the chemical composition of water from the spring and the chemical composition of the well located to the north is considerably more than the difference between the chemical compositions of the spring and the well located to the south.
Summary and conclusion
Based on the geological studies of this research, the Cheshme Ali spring in Shahre Rye appears from the Karstic Tizkooh formation (Fig. 2) and the geological structure shows a northerly direction for the slopes of the layers in Tizkooh formation, and an east-westerly direction for the appearance of the spring water (Fig. 3 and Fig. 9). The spring’s flow is disseminated and the spring is of Karstic - fault type (table 1). The discharge of Cheshme Ali corresponds entirely to rainfall and is influenced a lot by it (Fig. 5). The condition of groundwater table of the well and the spring (Fig. 6, A) and the water level potential of the spring and its surrounding wells underlines the existence of two different hydraulic environments (Fig. 6, B). Moreover, from the aspect of potential groundwater column, there is a large difference between the groundwater table potential of the spring and the potentials of the two wells to the north and south of the spring (Fig. 7and8). From a qualitative aspect, the quality of spring water differs greatly from the quality of water from the wells located to the north and south (table 2).
The results of this research are as follows:
1. The study of geologic, structural geology and the geological section shows the water in the Cheshme Ali of Shahre Rye is originating from the Karstic formation of Tizkooh that layers sloping are to the north, the spring water appears from the site of the Rye fault and then flows to the west.
2. The studies have proven that Cheshme Ali to be a Karstic – fault spring with disseminated flow, whose discharge is influenced by rainfall and condition of groundwater level and the table which underlines the alluvial aquifer shows lack of relation between two alluvial and karstic aquifers.
3. The water quality analyses show a great difference between the specifications of the spring water and its surrounding wells groundwater.
4- The north Rye fault mechanism are formed two different groundwater environment ( Karstic and alluvium) and however different groundwater conditions between north and south of alluvium.

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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