Journal of Engineering Geology

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Carbonate soils are different from silicate soils respect to their origination and engineering behavior. Particles of these soils are mainly residual or debris of sea animals or plants with large amount of calcium carbonate. They also may be chemical sedimentation of calcium carbonate over other soil particles in specific region of seas and oceans. The most important characteristic of these soils is the crushability of their aggregates under loading which is mainly due their shape and also small voids inside of them.  Crushability and subsequent volume changes in carbonate soils have caused many engineering problems in some geotechnical structures such as ...../files/site1/files/0Extended_Abstract5.pdf

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Introduction
Study on the main characteristics of strong ground motions, has relatively long history. The observations and investigations on the structural damages after strong earthquakes such as Northridge 1994 in California, Kobe 1995 in Japan, Tabas 1978 and Bam 2003 in Iran, are representatives of the destructive effects of strong near-field records. The most important specification of the near-field records which distinguish them from far-field records, is their ability to generate energized and relatively short-duration acceleration spikes as well as high amplitude and long-domain velocity pulses. Moreover, according to the lack of accurate statistical profiles as well as many deficiencies, processing the spectral existent data is not able enough to fully explain the seismic tremors. Based on the fact that the great earthquakes have long recurrence interval and also many high seismic zones of Iran do not possess strong tremors, hence generating and simulating feasible great events is required by applying closed form models and analysis of available data. In this study, in order to simulate the existent pulses in the time history of near-field records, the developed mathematical configuration is presented by analytical comprehensive attitude on the closed form model by Mavroeidis and Papageorgiou (2003).
Material and methods
Simulation of strong ground shakings, especially in areas where there is limited recorded data, plays a key role in assessing dynamic behavior of structures. Owing to unique characteristics of strong near-field ground motions, it is not possible to determine exact effects of these strong records on structures using simplified mathematical models. It is feasible to develop more complicated models which represent much more characteristics of near-field ground motions. Mavroeidis and Papageorgiou (2003) studied the parameters affecting near-fault ground motions. Their studies resulted in introducing a mathematical model capable of interpolating velocity pulses of near-field earthquake records (MP model). This closed-form MP model interpolates long duration pulses using a set of input spectral parameters.
 The pulse period, the pulse amplitude, the number and phase of half cycles are the key parameters that define the shape of velocity pulse. Thus, a four-parameter model has been developed to describe velocity pulses which contain forward directivity effects. In this research, it was observed that by using a combination of cubic and exponential terms, an enhanced model for interpolating the pulses presented in near-field earthquake records could be achieved (EMP model). Figure 1 shows the analytical interpolation of acceleration and velocity time histories using MP and EMP models.
 
Figure 1. Fitting of acceleration time histories with MP and EMP models
 
Results and discussion
Based on the obtained results, it is observed that there is a striking similarity between analytical characteristics obtained by actual earthquake records and mathematical pulses. Moreover, using the enhanced closed-form model (EMP model) reduces discrepancy between the results obtained under actual and the synthetic earthquake records.
Conclusion
Findings of this research reveal that equivalent pulses could be a good representative of actual earthquake records analytically, in order to assess the seismological characteristics of these tremors. It is worth mentioning that modelization of forward directivity pulses displayed in time history of strong ground shakings, is an efficient measure in evaluating seismic response of structures. In addition, due to stochastic nature of earthquakes, computational uncertainties and descriptive limitations of analytical parameters, using closed-form models require a high level of accuracy../files/site1/files/124/8nazari%DA%86%DA%A9%DB%8C%D8%AF%D9%87.pdf
 

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Introduction
Stone column installation method is one of the popular methods of ground improvement. One of the common uses of stone columns is to increase slope stability. Several studies have been performed to examine the behavior of stone columns under vertical loads. However, limited research, mostly focused on numerical investigations, has been performed to evaluate the shear strength of soil reinforced with stone column. The study presented herein is an experimental program, aimed to explore the shear strength of loose sand bed reinforced with stone column. Direct shear tests were carried out on specimens of sand bed material, stone column material and sand bed reinforced with stone column, using a direct shear device with in-plane dimensions of 305*305 mm² and height of 152.4 mm. Experiments were performed under normal stresses of 35, 55 and 75 kPa . In this study, 4 different area replacement ratios (8.4, 12, 16.4 and 25%), and 3 different stone column arrangements (single, square and triangular) were considered for investigation. The obtained results from this study showed that stone column arrangement had an impact on improving the shear strength of stone columns. The most increase in shear strength and stiffness values was observed for square arrangement of stone columns and the least increase was for single stone columns. This study also compares the equivalent shear strength values and equivalent shear strength parameters (internal friction angle and cohesion) measured during experiments with those predicted by analytical relationships. Results show that shear strength values and shear strength parameters measured from experiments are higher than those obtained from analytical relationships. Accordingly, a corrective coefficient was calculated for each column arrangement to represent the correlation between experimental and analytical results.
Material Properties of Loose Bed and Stone Column
Fine-grained sand with particle size ranging from 0.425 to 1.18 mm was used to prepare loose sand bed, and crushed gravel with particle size ranging from 2 to 8 mm was used as stone column material. The sand material used as bed material had a unit weight of 16 kN/m³ and a relative density of 32.5%, and the stone material used in stone columns had a unit weight of 16.5 kN/m³ and a relative density of 80%. The required standard tests were performed to obtain the mechanical parameters of bed material and stone column material. As the diameters of model scale stone columns were smaller than the diameters of stone columns installed in the field, the particle dimensions of stone column material were reduced by an appropriate scale factor to allow an accurate simulation of stone columns behavior.
Testing Procedure
In this study, large direct shear device with in-plane dimensions of 305*305 mm² and height of 152.4 mm was used to evaluate the shear strength and equivalent shear strength parameters of loose sand bed reinforced with stone column. Experiments were performed under normal stresses of 35, 55 and 75 kPa.
Two class C load cells with capacity of 2 ton were used to measure and record vertical forces and the developed shear forces during the experiments, and a Linear Variable Differential Transformer (LVDT) was used to measure horizontal displacement. All achieved data from the experiments including data on vertical forces, shear forces and horizontal displacements were collected and recorded using a data logger, and an especial software was used to transfer data between the computer and the direct shear device. All specimens were sheared under a horizontal displacement rate of 1 mm/min.
Testing Program
Experiments were performed on single stone columns and group stone columns arranged in square and triangular patterns. The selected area replacement ratios were 8.4, 12, 16.4, and 25% for single stone columns, and 8.4, 12 and 16.4% for square and triangular stone column arrangements. To eliminate boundary effects, the distance between stone columns and the inner walls of the shear box was kept as high as 42.5 mm. In total, 12 direct shear tests were carried out, including 2 tests on loose sand bed material and stone column material, and 10 tests on stone columns with different arrangements. From the tests performed on group stone columns, 4 tests were performed on single stone columns, 3 tests on stone columns with square arrangement and 3 tests on stone columns with triangular arrangement. Hollow pipes with wall thickness of 2 mm and inner diameters equal to stone column diameters were used to construct stone columns. To prepare the specimens, first, the hollow pipes were installed in the shear box according to the desired arrangement. Then, bed material with unit weight of 16.5 kN/m³ was placed and compacted in the box in 5 layers, each 3 cm thick. Stone material was uniformly compacted to construct stone columns with uniform unit weight. The compaction energy was 67 kJ/m³ in all tests.
Results and discussion
In this paper, the behavior of stone columns under shear loading was experimentally investigated in large direct shear device by performing tests with different area replacement ratios (8.4, 12, 16.4, and 25%), different stone column installation arrangements (single, square and triangular), and different normal stresses (55, 75 and 100 kPa). The key findings of this study are as follows:
1. Shear strength increases with increase of area replacement ratio due to the higher strength of combined soil-stone column system, and due to the increase of stone column area effective in shear plane. The amount of shear strength increase with area replacement ratio is low for ratios lower than 15%. However, this amount is higher for area replacement ratios higher than 15%.
2. For stone columns with equal area replacement ratios, higher shear strength was mobilized in stone columns with square and triangular installation arrangements compared to single stone columns. Among the installation patterns investigated in this study, stone columns with square arrangement experienced the highest increase in shear strength value, while single stone columns experienced the lowest. One of the reasons of shear strength increase in square and triangular patterns is the increase of confining pressure applied by stone columns to the soil between them. Another reason is the increase the total lateral surface by changing the column arrangement from single column to square and triangular patterns. This increased lateral surface increases the lateral force imposed on the stone columns, resulting in higher shear strength mobilization of stone material.
3. The slope increase of shear strength-horizontal displacement curves shows that soil-stone column system has higher stiffness than loose sand bed, and this stiffness varies with area replacement ratio and installation pattern. The maximum stiffness values refer to stone columns installed in square pattern and the minimum values refer to single stone columns. In general, stone column installation pattern has an effective role in increasing stiffness.
4. Results show that shear strength parameters increase in soil reinforced with stone column. The maximum increase in internal friction angle refers to stone columns with square pattern and the minimum increase refers to single stone columns.
5. The equivalent shear strength values measured from experiments are higher than those obtained from analytical relationships. Accordingly, it is conservative to use analytical relationships to calculate shear strength parameters. It is worthy to mention that these relationships assume that the value of stress concentration ratio is equal to 1. Results from this study indicate that the value of stress concentration ratio should be accurately calculated and used in the relationships.
6. As discrepancy was observed between values measured from experiments and those obtained from analytical relationships, corrective coefficients were calculated to modify analytical relationships. These coefficients were computed and presented based on stone column installation pattern, area replacement ratio and the applied normal stress values../files/site1/files/133/2Extended_Abstracts.pdf 

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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
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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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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Introduction
Stone column installation method is one of the popular methods of ground improvement. Several studies have been performed to investigate the behavior of stone columns under vertical loads. However, limited research, mostly focused on numerical investigations, has been performed to evaluate the shear strength of soil reinforced with stone column. The stress concentration ratio (n) is one of the important parameters that uses in soil improvement by stone column method. Stress concentration ratio is the ratio of the stress carried by stone column to that carried by the surrounding soil. In this paper, the results of a laboratory study were used to examine the changes in the stress concentration ratio when normal and shear stress applied. Direct shear tests were carried out on specimens of sand bed material, stone column material and sand bed reinforced with stone column, using a direct shear device with in-plane dimensions of 305*305 mm and height of 152.4 mm. Experiments were performed under normal stresses of 55, 77 and 100 kPa. In this study, three different area replacement ratios (8.4%, 12%, 16.4%), and three different stone column arrangements (single, square and triangular) were considered for investigation. Loose sand and crushed gravel were used to make the bed and stone columns, respectively. In this study, the equivalent shear strength and equivalent shear parameters measured from experiments were also compared with those predicted by analytical relationships at stress concentration value of 1 and stress concentration value obtained from experiments.
Material Properties
Fine-grained sand with particle size ranging from 0.425 to 1.18 mm was used to prepare loose sand bed, and crushed gravel with particle size ranging from 2 to 8 mm was used as stone column material. The sand material used as bed material had a unit weight of 16 kN/m³ and a relative density of 32.5%, and the crushed stone material used in stone columns had a unit weight of 16.5 kN/m³ and a relative density of 80%. The required standard tests were performed to obtain the mechanical parameters of bed material and stone column material. As the diameters of model scale stone columns were smaller than the diameters of stone columns installed in the field, the particle dimensions of stone column material were reduced by an appropriate scale factor to allow an accurate simulation of stone columns behavior.
Testing Procedure
In this study, large direct shear device was used to evaluate the shear strength and equivalent shear strength parameters of loose sand bed reinforced with stone column. Experiments were performed under normal stresses of 55, 75 and 100 kPa. Two class C load cells with capacity of 2 tons were used to measure and record vertical forces and the developed shear forces during the experiments, and a Linear Variable Differential Transformer (LVDT) was used to measure horizontal displacement. The main objectives of this study was to calculate the stress concentration ratio of stone columns in different arrangement. Stress concentration ratio is the ratio of the stress carried by stone column to that carried by the surrounding soil, and can be calculated using Equation 1. For this purpose, the direct shear device was modified. Two miniature load cells with capacity of 5 kN were employed. The load cells were mounted on the rigid loading plate with dimensions of 305*305 mm² and thickness of 30 mm, as shown in Figure 1, All achieved data from the experiments including data on vertical forces, shear forces and horizontal displacements were collected and recorded using a data logger, and an especial software was used to transfer data between the computer and the direct shear device. All specimens were sheared under a horizontal displacement rate of 1 mm/min.
Experiments were performed on single stone columns and group stone columns arranged in square and triangular patterns. The selected area replacement ratios were 8.4, 12 and 16.4% for single, square and triangular stone column arrangements. To eliminate boundary effects, the distance between stone columns and the inner walls of the shear box was kept as high as 42.5 mm. In total, 11 direct shear tests were carried out, including two tests on loose sand bed material and stone column material, and 9 tests on stone columns with different arrangements. From the tests performed on group stone columns, 3 tests were performed on single stone columns, 3 tests on stone columns with square arrangement and 3 tests on stone columns with triangular arrangement. Hollow pipes with wall thickness of 2 mm and inner diameters equal to stone column diameters were used to construct stone columns. To prepare the specimens, first, the hollow pipes were installed in the shear box according to the desired arrangement. Then, bed material with unit weight of 16.5 kN/m³ was placed and compacted in the box in 5 layers, each 3 cm thick. Stone material was uniformly compacted to construct stone columns with uniform unit weight.
Results and discussion

1. The SCR value increases for settlement up to 3 mm and then decreases with increasing the horizontal displacement and then approaches almost a constant value. Results also show that stress concentration ratio decreases with increase of stone column diameter. Results show that the value of stress concentration ratio in square pattern is higher than that in single and triangular pattern. Moreover, results show that stress concentration ratio decreases with increase of normal stress.
2. The value of the internal friction angle in (peak) state, for loose bed increases from 33 to 40 degrees in square arrangement and in the corresponding state of displacement of 10 % from 30 degrees in a loose bed increase to 32 degrees, for loose sand reinforced with stone column. Shear strength increases with the increase of modified area ratio in all stone column installation patterns in both the peak and the corresponding state of the horizontal displacement of 10%.
3. For stone columns with the same modified area ratio, the installation pattern has an effective role in defining the shear strength. Group stone columns mobilize higher shear strength compared to single stone columns. Among the installation patterns investigated in this study, stone columns with square arrangement experienced the highest increase in shear strength value while single stone columns experienced the lowest.
4. The equivalent shear strength values measured from experiments are higher than those obtained from analytical relationships. Accordingly, it is conservative to use analytical relationships to calculate shear strength parameters. It is worth explaining that these relationships assume that the value of stress concentration ratio is equal to 1. Results from this study show that the value of stress concentration ratio should be accurately calculated and used in the relationships.
5. Comparison between shear strength parameters obtained from experiments and those predicted by analytical relationships shows that in single stone columns, the value of stress concentration ratio should be 3 to 4.5, and in square and triangular patterns, this value should be 6 to 7 and in triangular patterns 4.5 to 5, respectively, to achieve good agreement between experimental and analytical results in peak condition. In horizontal displacement 10% the value of stress concentration ratio should be 2.5 to 3, in single, square and triangular patterns, to achieve good agreement between experimental and analytical results../files/site1/files/151/2.pdf

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Chahar-Gonbad region of Kerman province is geologically located in the southern part of central Iran zone, dominantly in Uromieh-Dokhtar volcanic belt. In this region, many high potential prospects, specially Cu-Au mineralization, have been detected during large scale exploration and reconnaissance phases. In this paper, remote sensing and field geophysics were used for alteration mapping on the surface and ore body delineation on the subsurface, respectively. To this end, we used an ASTER satellite image and different maps were generated by spectral technics such as false color composites and spectral ratios. Results showed argillic (and phillic) alteration in Bab-Zangoeie area is surrounded by propylitic alteration, which could be a promising evidence for Cu mineralization. Integrating these results with previous exploration studies led to selecting target area selection for ground study and field geophysics. We used both induced polarization (IP) and resistivity (RS) methods as two powerful geoelectrical methods by a pole-dipole array along four profiles. After preprocessing analysis, forward and inverse models were constructed in 2D section and 3D overlay model of joint IP/RS anomalies were constructed. Based on the obtained results, the deposit in depth where we proposed drilling targets. Further drilling operation have proved the mineralization in our proposed targets../files/site1/files/152/%D9%86%D8%B8%D8%B1%DB%8C.pdf