محمدکاظم جعفری

The determination ofgeological subsurface strata and shear wave velocity profiles is one of the most important engineering measures for seismic design and site effects studies. Recently, the use of seismic geophysical methods in engineering geological studies for this purpose has become widespread. In this paper, the accuracy and efficiency of seismic geophysical methods with active and passive seismic source in determining the subsurface geological structure of a selected site in the city of Abasabad in northern Iran have been studied. To this end, first, by conducting several exploratory boreholes, the subsurface geological structure of the study site up to a depth of 70 meters was carefully determined using engineering geological experiments. The results of this section showed that the shallow sediments of Abasabad site are mainly composed of sandy soils with four separate geological layers. In the next step, in two other separate boreholes, seismic geophysical experiments with active source of down-hole test were performed in order to accurately determine the shear wave velocity profile in different layers. In addition, in the next phase, using the array microtremor recording method, which is a new seismic geophysical method of passive-source type, to determine the subsurface geological structure of the study site in the form of shear wave velocity profiles. It should be noted that the array microtremor recording was performed using fifteen different arrangements of receptors (with different numbers and distances of receptors) and by two analyzing methods including F-K and SPAC. The results of these studies showed that both active and passive seismic geophysical methods had acceptable performance in determining the subsurface geological stratification of the site. It also could be inferred that the down-hole test with high accuracy determines the shear wave velocity in each layer compared to the array microtremor method but requires artificial production of seismic waves and borehole drilling. Array microtremor method without the need for drilling and production of artificial seismic waves has high efficiency in determining the subsurface layering and estimating the shear wave velocity of each layer and in general the results of this paper showed that in estimating the shear wave velocity compared to down-hole method shows up to 10% error.

Earthquake ground motions are generally recorded by digital accelerometers in three orthogonal components (two horizontal and one vertical). The vertical component is typically ignored and two horizontal records are used for the response analysis of most structures. In two-dimensional time history analysis, a stronger horizontal component of the as-recorded ground motion is generally used to evaluate the structural responses. However, the horizontal strong ground motion depends on the orientation of the sensors as installed in the field. Simple trigonometric calculations demonstrate that by rotating the sensors, different waveforms are recorded for a specific ground motion. Considering that the orientation of the sensors is random compared to the orientation of the structures and causative fault, the question arises as to what percentage of confidence the use of as-recorded ground motions leads to the maximum desired responses.     To investigate this issue, based on the information and specifications of embankment dams in the earthquake-stricken areas of Kermanshah and considering the appropriate statistical distributions, 1000 numerical models of embankment dams were simulated using the Monte Carlo simulation method. In the next step, each of the 4 selected records of Sarpol-e Zahab, Kerand, Goorsfeid, and Javanrood were rotated in different angles from 0 to 180 degrees with 10-degree steps and applied to each of the numerical models of the dam. Equivalent linear time history analysis was performed for each of the simulated numerical models of the dam resulting in a total of 72,000 (18 * 4 * 1000) analyses. The values of maximum acceleration, velocity, displacement, and velocity-to-acceleration ratios of the dam crest (and the directions associated with each of these responses) were calculated for different stations. Using the simulation results, the probability that as-recorded accelerations would lead to critical responses was calculated. The results can be summarized as follow: Critical directions depend on the characteristics of the dam, input motions, and the type of the response; The probability of occurrence of critical responses in the case of using recorded accelerations depends on the input motion and the type of response considered; for example, the probability that the Sarpol-e-Zahab record would lead to critical displacement is close to 10%, while the same record with a probability of approximately 30% leads to a critical velocity or acceleration. In Javanrood station, the results are different from the previous results, and in the case of using the recorded acceleration, the probability of occurrence of critical displacement is close to 40%; Histograms of critical directions show that in general, no specific statistical distribution can be considered for critical directions; The higher the PGA value of the record, the lower the scatter of critical directions of the record.

In current modern cities, the use of buried pipelines in the conveying of vital fluids such as water, oil, and gas have become very important. Investigations on the behavior of the buried pipelines after the occurrence of the severe earthquakes have indicated that one of the primary sources of the failures of these kinds of linear structures were due to surface fault rupture. Therefore, if the buried pipelines are designed and implemented correctly, the permanent ground displacement due to the movement of the bedrock fault will not lead to such rupture of the pipes. On this basis, different researchers have concentrated their studies on investigating the interaction of pipe and soil during the permanent ground displacement. Due to the difficulty and cost of laboratory tests on this phenomenon, the number of available experimental data is very few. On the other hand, analytical studies have various limitations and complexities that have made it difficult for engineers to use these methods. In addition, numerical methods used to study the interaction of pipes and faults are mostly prepared for academic environments. These numerical approaches usually need the knowledge of soil or pipe advanced constitutive models and require the familiarity with mathematical parameters necessary for the convergence of the computational efforts.In order to investigate the behavior of buried pipes against faulting displacement, in this paper, a numerical method has been developed by combining finite difference and Newton multivariable techniques. The equilibrium equation of forces in x and y directions along with the equilibrium equation of bending moment for an infinite section of the pipe under the influence of the displaced soil pressure has been obtained first. Then the system of equations for all of the discretized nodes of a pipeline has been solved using the proposed hybrid method. The proposed method simultaneously considers the nonlinear behavior of pipes, soil equivalent springs, and large strains in the beam-spring model. In addition, to more precisely assess the shear factor in the beam behavior, the Timoshenko beam model has been applied to model the pipe.The validity of the proposed method has been performed using the results of a laboratory centrifuge test on HDPE pipe and 90° normal fault. In addition, this hybrid method is also validated with the results of a finite element numerical analysis on 70° normal fault and API5L-X65 oil transfer pipe. Comparison of the obtained results for different parameters such as longitudinal strains, settlement, and flexural bending of the pipes shows that the presented numerical method is very suitable in predicting the interaction behavior of pipes against dip-slip faults. At the same time, a lower computational effort has been required to arrive in the final answers. In addition, using the proposed numerical method, the effect of fault zone width with values equal to 0.001, 10, 30, 60, and 100 m on the behavior of a pipeline against a normal 70-degree fault has been investigated. The results of this study show that increasing the width of the fault zone significantly reduces the amount of tensile strain in the pipes. Also, increasing the width of the fault zone causes the pipe to rupture from two different points, while in the small fault width equal to 0.001 m, the pipe failure occurs only at one point. Maximum bending moment and pipe curvature also increased with decreasing fault width.

The artificial neural network (ANN), one of the most powerful tools of artificial intelligence, was used to control the seismic responses of the cross section, and to predict earth dam seismic responses rather than utilizing dynamic time-based analyses. In terms of the artificial neural network, apart from the aforementioned ANN-based applications in various engineering problems, an increasing number of articles have been published over the last decade where the efficient implementation of ANNs in geotechnical earthquake engineering is presented. Most of these studies focus on liquefaction potential under seismic excitations, which is an extremely computationally intensive issue and therefore suitable for ANNs. In some of the studies in this field, the applicability of ANNs in soil dynamic analysis was examined. In addition to the generation of spectrum compatible accelerograms, prediction of earthquake parameters, wave propagation approximations, estimation of peak ground acceleration using microtremors, and the detection of earthquake electric field patterns. Not much has been done into predicting the seismic responses of embankments and earth dams using artificial neural networks tools. The first study on the domain was carried out by Tsompanakis et al. [1] in 2009 in which using the artificial neural network, a seismic response (maximum horizontal acceleration) of homogeneous and symmetric embankment in different locations was predicted. Although being a case study on a simple embankment, earthquake records (accelerograms) were used, which contained a variety of frequency concepts, simplicity or complexity, and various PGA levels, in addition to a general neural network that could be used in all PGA levels the seismic response was not accurately predicted. The objective of the present study was to investigate the ability of the artificial neural network to reach the dynamic response of the embankment and earth dams under seismic loads and different levels of intensity. In other words, it was planned to reduce the heavy cost of calculating the applicable issue in seismic geotechnical engineering. To fulfill the aim, a comprehensive study was carried out and various parameters were evaluated. According to the results, the artificial neural network could reach a good approximation of the seismic response of embankments and earth dams. Although comparing the results of artificial neural networks segmented from generic artificial neural network showed the accuracy of the estimated artificial neural network structured for each PGA level, especially in the linear region, the study was successful in eliminating the defects of previous research, making a perfect arrangement for a generic artificial neural network to be used for this type of neural network to achieve a favorable estimation of all PGA levels. Finally, it can be concluded that considering the complexities of the problem and the performance of the artificial neural networks in solving them, as well as the history of successful performance reports on this tool in other similar applications, the application of Artificial Neural Networks proved useful for estimating and predicting seismic responses of embankments and earth dams. Using artificial neural networks to meet this purpose would reduce the cost of calculating the seismic response assessment of embankments and earth dams. Therefore, applying this tool in the complicated field of seismic geotechnical engineering may be highly promising. Overall, future developments in this research field and promotions in artificial neural network training in other situations by changing the dimensions and properties of materials and load conditions would realize this idea and create a more general neural network for this application. 

In most studies of faulting-soil-foundation-structural interaction, the structural effects is considered by modeling the equivalent hardness or adding equivalent overload to the foundation. Consequently, direct modeling of the structure is avoided in laboratory and numerical models. Based on the above-mentioned remarks, direct modeling of the structure seems to allow a better understanding of the structure-foundation effect on the distribution of surface fault rupture. In the current study, a 2D finite element numerical modeling of structure-foundation-alluvium interaction has been made by applying reverse surface faulting. The structures are modeled as two span frames with 3 and 7 floors with strip foundation. The effects of different factors on the interaction phenomenon including: location of the structure (Table 1), number of floors and foundation thickness have been studied parametrically. The results of the parametric studies indicated that the most critical situation of the structures occurs when it is located on the hanging wall with a 15 to 25 meters far from the free field fault outcrop. Related to the structural location, the effect of increasing floor number on structural deformation is not unique. Nevertheless, this phenomenon increases the internal forces of structural members. In fact during surface fault ruptures, greater amounts of shear forces and bending moments was created along the beam floors and foundation structures by incasing the floor numbers. Furthermore, increasing the foundation thickness reduces the induced shear forces and moments of the structural members. Consequently, it is recommended to use the foundations with a high thickness for improving the structural performance against surface fault ruptures.

Seismic loads may damage municipal solid waste landfills (MSWLF) through the relative movements within the waste, bottom lining system, cover system, foundation, and interfaces. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. In the present study, experimental investigations were conducted in order to evaluate role of in-soil base isolation on seismic response of the Kahrizak MSW landfill. Shaking table tests were conducted on the MSW embankment isolated by semi-elliptic shaped liners and subjected to harmonic sinusoidal base excitations. Furthermore, the shaking table model was simulated by numerical analysis. The results of the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. Subsequently, the behavior of the numerical model was evaluated for different parameters. A reasonable agreement was found between the results of the physical model and the numerical model in prototype scale. The efficiency of in-soil isolation increases with increasing the amplitude of input motion. The results show that increasing the shear modulus reduces the amount of spectral amplification and relative displacement. It was also observed that as the age of the MSW increases, base isolation increases the displacement and crack width. Moreover, employing flat liner facilitates the movement of the ridge to the sides; and the concave liner prevents the wedge to move and, hence the quantity of settlement is reduced.

Isolating the earth structures such as retaining walls, bridge abutments and buried pipes using the compressible materials is a novel solution to reduce the lateral earth pressure. In this technique, a layer of the compressible material with relatively small stiffness and limited thickness is implemented between the retaining wall and the backfill. This material acts as a seismic buffer due to its high compressibility, which absorbs the excess dynamic earth pressure significantly and attenuates the transmitted force to the retaining structure. Choosing the appropriate materials for construction of seismic buffers is based on their physical and mechanical properties as well as cost-effective considerations. Most of the previous studies were focused on some specific materials such as expanded polystyrene (EPS) foam blocks and tire chips. This paper investigated the performance of polymeric seismic buffers made from Polyurethane (PU) foam on seismic response of non-yielding retaining walls. PU foam has appropriate properties and eliminates some of limitations on materials used in previous studies. The purpose of current study was to evaluate the applicability of PU foam as a new option for construction of seismic buffers with regard to its benefits. Hence, the behavior of non-yielding retaining walls was investigated in two conditions of with and without presence of the seismic buffers by conducting of a series of 1g shaking table tests. Seismic buffers included PU foam blocks, which were prepared by injecting foam into the cubic molds and spraying a certain amount of water on the specimens. A total of 13 tests were carried out on two models (retaining wall with and without seismic buffer) with changing the input base acceleration from 0.07g to 0.46g. The input motion was a horizontal sinusoidal excitation with a constant frequency of 3.6 Hz, which was applied for 10 seconds to the longitude direction of the model. The model responses including wall force and backfill soil displacement were measured during the excitation in each test. The results showed that the implementing seismic buffers made from PU foam reduce the total and dynamic horizontal wall forces on average of 30% and 45%, respectively. The force attenuation and backfill soil displacement have an inverse relationship to each other. For an equal Normalized compressible inclusion stiffness, this type of foam has a better performance in comparison with similar materials such as expanded polystyrene foam (EPS). Moreover, it is identifying that the force attenuation is not uniform along the height and the maximum attenuation occurs at the top of the retaining wall. The force distribution is triangular for static conditions. As the peak base acceleration is increased and the contribution of dynamic loads on upper elevations is increased, the force distribution becomes nonlinear. Therefore, at earthquakes with moderate to high intensity, the point of application of total horizontal force is transferred to the upper elevations of the retaining wall. Moreover, it is revealed that the efficiency of this technique increases for moderate to high-intensity earthquakes (acceleration amplitude more than 0.24g).

Seismic loads may damage municipal solid waste landfills (MSWLF) through the relative movements within the waste, bottom-lining system, cover system, foundation, and interfaces. These movements can disrupt the performance of drainage and gas
collection systems, thereby resulting in environmental pollutions. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by absorbing the imparted energy of earthquakes through the sliding mechanism. It has been found that a high-strength geomembrane placed over the other smooth and lubricated geomembrane sheets (e.g., geomembrane/geomembrane) constitutes a liner that is well suited for this application. In the present study, experimental investigations were conducted in order to evaluate the role of in-soil base isolation on seismic response of the Kahrizak MSW landfill with more than 7000 tons waste disposal daily in Tehran, Iran.Results of geophysical and geotechnical investigations in the landfill site are presented in detail. Shaking table tests were conducted on the MSW embankment isolated by semielliptic shaped liners and subjected to harmonic sinusoidal base excitations. Two types of base isolation system were employed in the experiments. The results of the isolated and non-isolated cases are compared in terms of permanent displacement and seismic response. It has been observed that, at all elevations, the spectral accelerations within the waste decreased by base isolation, especially for the more intense excitations. Although the fundamental period of the embankments significantly increased by increasing the amplitude of input motion, the base isolation mechanism did not affect the system period. In fact, isolation liners can significantly reduce
the seismic shear forces and accelerations transmitted to the landfill crest. The sliding displacement that is required to provide efficient soil isolation is in the range of permissible displacements for MSW landfills. Results of the present study demonstrate a suitable application of geosynthetic liners for seismic retrofitting of landfills.

In this research, perfectly matched layer has been implemented in the finite element method to simulate the radiation damping for soil-structure interaction analysis application. The perfectly matched layer (PML) has the ability to absorb and attenuate scattered waves under any angle of incidence and frequency, such that with the minimum dimensions of the modeling and the minimum amount of calculations, high-precision responses can be achieved. In order to time domain dynamic analysis by finite element method, a program is written utilizing MATLAB mathematical language, which is capable of analysis of different geometries, layering and dynamic/seismic loading in models with linear elastic behavior. The present program uses four-noded quadrilateral elements and uses the implicit Newmark method to solve the dynamic equation. The feature of theprogram is the implementation of PML, which can address the simulation of radiation damping in the finite element method correctly. This is done by rewriting the PML formulation, implementation in the finite element method, and step-by-step verifying the analysis of dynamic problems. First of all, to verify the dynamic analysis performance of the program, three simple examples have been solved, and the results show that theyare consistent with existing theories and the literature. Next, using PML, the problem of a rigid massless foundation vibration has been studied. Computing the impedance/compliance functions and comparing them with analytical or semi-analytical approaches existing in the technical texts, the efficiency and the precision of PML for surface loading conditions has been evaluated. In the frequency domain, the results are in good agreement with the previous studies. Besides, comparing the response from the reduced model (using PML) with the expected response from the extended mesh indicates that there is a complete match in the time domain. It is worth noting that this match is achieved while the model dimensions and the volume of data storage have been drastically reduced, but the accuracy of the answers has not varied. This reduction of dimension is such that if PML is located at a distance of up to a quarter of the foundation width, similar responses to larger models can be achieved.

Intergranular water in granular soils, such as sands, can produce apparent cohesion in the soil that results in changing the behavior of soil while shearing. Apparent cohesion in wet granular soil arises from surface tension and capillary effects of the small water bridges between adjacent soil grains. This intergranular water exerts an attractive force between the grains and an apparent cohesion is produced. Induced cohesion in wet soil depends on the amount of intergranular water within the pores of soil.
In this investigation, the effect of water content on the sand strength parameters (such as cohesion and internal friction angle) and deformational parameter (such as failure strain) were studied. For this purpose, some series of direct shear tests were conducted in which soil water content and its vertical stress were widely changed. Samples with 0% (dry condition), 5%, 10%, 15% and 24% (saturated soil condition) were examined in nine vertical stress (that categorized into two fields: low and high vertical stress condition). The low normal stress condition contained 0.015, 0.03 and 0.045 kgf/cm2. Vertical stresses of 0.1, 0.25, 0.4, 0.6, 0.85 and 1.25 kgf/cm2 were determined as the high stress condition. The importance of low stress condition is to obtain the exact behavior of soil at low stress condition that corresponds to vertical stresses in small scale physical models.
In this research, the investigation is based on two points of view: 1) from deformational point of view, the most important result is the relationship between soil’s water content and its failure strain. Adding water to sandy soil decreases its failure strain and it has its lowest value at about 5% water. It means that wet soil behaves more brittle than dry one. In this point of view, also a good similarity can be observed between the results of direct shear tests and physical models results (D0/h parameter); 2) From strength point of view, in low vertical stress tests, with an increase in water content to about 5%, internal friction angle increased and beyond this limit decreased. As in this situation, almost a constant cohesion obtained from the data, it can be concluded that by an increase in water content to about 5%, soils shear strength also increases and then decreases (in low stress condition that it corresponds to physical modeling stress level). Besides, discussions were made on the behavior of sand at high stress level and in residual condition.
Above-mentioned results have been employed to interpret the result of some fault rupture physical modeling tests on wet sand. The pure sand was used with various water content (0% (dry), 5%, 10% and 15%). One of the important results that can be achieved in physical modeling tests is the normalized required fault displacement (D0/h) at the bedrock, in which the fault rupture trace reaches the ground surface. Obtained results show that as the water content increased up to a certain value (around 5%), the D0/h parameter decreases at first and beyond this limit it increases a little. Generally, it seems that soil behaves more brittle when it is wet. Besides, it is in its most brittle behavior when the water content of soil is around 5%. The observed trend of D0/h parameter is almost similar to what observed on failure strain of the wet sand that was achieved by direct shear tests.

Ports are very important nodes of national and international transportation networks and play a crucial role in economic activity of the nations. It is widely acknowledged that the port facilities should be designed carefully to tolerate against the strong earthquakes. On the other hand, uncertainty of structural and geotechnical parameters has a significant impact on seismic performance of the marine systems. In most engineering practices, however, this impact is ignored and the designers prefer to estimate and employ some representative parameters. Therefore, realistic estimation of seismic performance of port structures requires a probabilistic approach based on appropriate involvement of soil and ground motion variability.
In this study, the caisson-type quay wall of Rokko Island is considered for the numerical analyses. The foundation and the backfill soils of this well-documented quay wall were liquefied during the Kobe 1995 earthquake, as resulted in approximately 4 m seaward displacement. It settled about 1 m to 2 m and tilted about 4 degrees outward. For nonlinear dynamic analyses in FLAC 2D, the UBCSAND constitutive model was employed in order to account for liquefaction of backfill and foundation soil. Soil is variable in the nature and its geotechnical parameters are rarely constant in spatial directions. Since the parameters of the employed constitutive model (UBCSAND) were totally correlated to the corrected standard penetration resistance (N1,60), there would be an excellent chance to generate numerous series of random field data through the interpolation of the available boring log data around the quay wall. The covariance of these random data was considered 45% and the mean values were extracted from the interpolation results of the available boreholes. Subsequently, nonlinear dynamic analyses were carried out by the generated random field data. Numerical modeling based on the deterministic parameters resulted in horizontal and vertical displacements of 4.7 m and 1.9 m, respectively. By applying uncertainty of the standard penetration test parameter in nonlinear dynamic analyses, the resulted quay wall displacements vary in the ranges of 4.7-5.7 m and 1.2-1.8 m, respectively, in the horizontal and vertical directions. These impressive changes indicate that the involvement of spatial variability of soil parameter has significant effects on the assessment of permanent displacement in the quay wall systems. This paper presents a reliable and simple method for consideration of spatial variability of standard penetration test results in dynamic analysis of gravity quay walls. The resulting numerical displacements can be employed for probabilistic seismic design of the quay wall.

Study of the seismic response of a site, requires the accurate estimation of the Shear modulus (G) and damping ratio (D) of under ground layers in that area. According to the unsaturated condition of an extensive part of the earth surface, it is necessary to perform unsaturated tests to determine dynamic or cyclic parameters of these regions. On the other hand, because of inherent complications of unsaturated testing equipment, this field of experience has had less attention. But in recent years by development of advanced experimental equipment some studies have been developed based on the dynamic parameters of unsaturated soils.
A large amount of the researches related to cyclic and dynamic parameters of unsaturated soils are the studies about determination of these parameters in very small strain levels (initial shear modulus and initial damping ratio) and the effects of some factors such as suction, mean net stress, suction history, anisotropy and pre-consolidation on them, using bender element technique and resonant column torsional shear apparatus. But there is less attention in experimental studies in the strain ranges of medium to large and determination of the parameters G (shear modulus) and D (damping ratio), and also the normalized shear modulus reduction and damping ratio curves for unsaturated soils.
In this research, it is tried to determine the shear modulus and damping ratio parameters in medium to large strain levels using suction controlled cyclic triaxial apparatus and study the effect of changes in matric suction and mean net stress on these parameters in a kind of unsaturated clay with plasticity index of 24 under high loading rates. In this regard, some tests are performed on different paths including two suction levels (zero and 300 KPa), in mean net stress level of 200 KPa and three deviatoric cyclic stress ranges (18, 42 and 81 KPa) up to 60 loading cycles. Also a comparison is done between the results obtained from the current research and the results of another research which was performed in the same paths on a fine grained soil with plasticity index of 12 using the same equipment.
The results of this research show that increase in suction level results in raising shear modulus and decreasing in damping ratio values. In addition in the same strain level, by increasing the number of loading cycles, the shear modulus values are increased and the damping ratio values are decreased.
Considering the results of current research (unsaturated cyclic tests on unsaturated normally consolidated fat clay with plasticity index of 24) with the results of another experimental research in the field of unsaturated cyclic tests on unsaturated normally consolidated lean clay with plasticity index of 12, in the same sample preparation process and the same stress paths, is indicated that the changes of the shear modulus values of the high plasticity samples are in the lower level related to the values of the samples with plasticity index of 12. In the other word, the increase in plasticity index decreases the stiffness of the samples considerably. But the change in damping ratio values is shown relatively the same trend in both groups of the samples.

In many large magnitude earthquakes, the causative fault propagates all the way up through the soil and interacts with surface structures. Over the last four decades, earthquake engineering research and practice have emphasized the dynamic response of soil and structural systems to ground oscillations. Even so, recent strong earthquakes (i.e. the 1999 Chi-Chi Taiwan earthquake and the Landers 1992 California earthquake) have caused major collapse to structures from surface fault ruptures. Previous research has not concentrated on studying the response of soil-structure systems to large displacements induced by surface fault ruptures. Although piles are usually used for protecting structures by reducing total and dierential settlements, they are not an acceptable treatment in supporting structures from surface fault rupture. Previous research has shown that piles usually follow fault rupture deformation and transfer it to the structure. Therefore, this behavior is a reason for the unsuitable performance of a piles group against fault rupture. In order to study the interaction of the soil and the piles group during reverse fault rupture carefully, in the rst step, the propagation of fault rupture in free eld is modeled. For this purpose, a 2D numerical model is veried by reduced-scale experiment results. In the numerical models, a nonlinear nite element method, using an elastoplastic constitutive model with Mohr-Coulomb failure criterion and isotropic strain softening characteristics, is used. For the main analysis, the eects of the presence of a piles group on top of the outcropping fault are simulated. The analysis results indicate that the presence of the piles group slightly modi es the fault rupture path.

The construction of underground tunnel plays a more and more important role in the development of big cities. One of the most important problems caused by the construction of the tunnel is that underground excavation will cause large settlement of the ground and buildings. Previous studied showed the difference between numerical and experimental results. In this study the case study of Niyayesh-Sadr tunnel is selected and the conditions of this project were applied. This tunnel is located at north of Tehran with a span of 14 meters which constructing with the multi drift method. During construction، this tunnel should pass near some buildings near Mahyar Street then the settlement of surface should be considered. Numerical methods in this study was performed with the finite element code with PLAXIS 2D and the effect of tunnel-adjacent interaction is investigated. In addition the effect of foundation stiffness and weight of the structure is considered in these analyses and the results are compared to the emphasis on tunnel surface structure interaction. Results show that the settlements of foundation are increased 15% due to interaction analysis respect to green field one. Varieties of structures along the tunnel in surface، different overburden depth of the tunnel and also location of building respect to the axis of the tunnel need several numerical models in one project. In this study، one simple approach is suggested to control structures against settlement and prevent using several models.

T‌h‌i‌s s‌t‌u‌d‌y h‌a‌s i‌n‌t‌r‌o‌d‌u‌c‌e‌d, d‌e‌s‌c‌r‌i‌b‌e‌d a‌n‌d c‌o‌m‌p‌a‌r‌e‌d t‌h‌e p‌e‌r‌f‌o‌r‌m‌a‌n‌c‌e o‌f t‌w‌o p‌o‌p‌u‌l‌a‌r i‌n‌t‌e‌g‌r‌a‌t‌i‌o‌n m‌e‌t‌h‌o‌d‌s f‌o‌r i‌m‌p‌l‌e‌m‌e‌n‌t‌i‌n‌g c‌o‌m‌p‌l‌i‌c‌a‌t‌e‌d e‌q‌u‌a‌t‌i‌o‌n‌s o‌f s‌o‌i‌l m‌o‌d‌e‌l‌s. G‌e‌n‌e‌r‌a‌l‌l‌y s‌p‌e‌a‌k‌i‌n‌g, a‌l‌l m‌e‌t‌h‌o‌d‌s c‌a‌n b‌e c‌l‌a‌s‌s‌i‌f‌i‌e‌d i‌n‌t‌o t‌w‌o c‌a‌t‌e‌g‌o‌r‌i‌e‌s o‌f E‌x‌p‌l‌i‌c‌i‌t a‌n‌d I‌m‌p‌l‌i‌c‌i‌t a‌p‌p‌r‌o‌a‌c‌h‌e‌s. T‌w‌o f‌a‌m‌o‌u‌s m‌e‌t‌h‌o‌d‌s o‌f t‌h‌e i‌m‌p‌l‌i‌c‌i‌t a‌p‌p‌r‌o‌a‌c‌h, t‌h‌e C‌l‌o‌s‌e‌s‌t P‌o‌i‌n‌t P‌r‌o‌j‌e‌c‌t‌i‌o‌n M‌e‌t‌h‌o‌d (C‌P‌P‌M) a‌n‌d t‌h‌e C‌u‌t‌t‌i‌n‌g P‌l‌a‌n‌e M‌e‌t‌h‌o‌d, (C‌P‌M), w‌h‌i‌c‌h a‌r‌e d‌e‌f‌i‌n‌e‌d u‌n‌d‌e‌r t‌h‌e f‌r‌a‌m‌e‌w‌o‌r‌k o‌f t‌h‌e R‌e‌t‌u‌r‌n M‌a‌p‌p‌i‌n‌g a‌l‌g‌o‌r‌i‌t‌h‌m, a‌r‌e c‌o‌n‌s‌i‌d‌e‌r‌e‌d i‌n t‌h‌i‌s s‌t‌u‌d‌y. B‌o‌t‌h t‌h‌e C‌u‌t‌t‌i‌n‌g P‌l‌a‌n‌e M‌e‌t‌h‌o‌d a‌n‌d t‌h‌e C‌l‌o‌s‌e‌s‌t P‌o‌i‌n‌t P‌r‌o‌j‌e‌c‌t‌i‌o‌n M‌e‌t‌h‌o‌d a‌r‌e e‌m‌p‌l‌o‌y‌e‌d i‌n o‌r‌d‌e‌r t‌o i‌m‌p‌l‌e‌m‌e‌n‌t a‌n a‌d‌v‌a‌n‌c‌e‌d c‌r‌i‌t‌i‌c‌a‌l t‌w‌o-s‌u‌r‌f‌a‌c‌e m‌o‌d‌e‌l, p‌u‌b‌l‌i‌s‌h‌e‌d b‌y M.T. M‌a‌n‌z‌a‌r‌i a‌n‌d Y.F. D‌a‌f‌a‌l‌i‌a‌s, i‌n 1997, f‌o‌r s‌a‌n‌d. S‌i‌n‌c‌e t‌h‌e C‌P‌P‌M a‌n‌d C‌P‌M m‌e‌t‌h‌o‌d‌s a‌r‌e i‌m‌p‌l‌i‌c‌i‌t, i‌t h‌a‌s a g‌r‌e‌a‌t a‌d‌v‌a‌n‌t‌a‌g‌e, a‌s b‌o‌t‌h s‌i‌z‌e‌s o‌f s‌t‌e‌p‌s r‌e‌m‌a‌i‌n s‌t‌a‌b‌l‌e. A c‌o‌m‌m‌o‌n w‌e‌a‌k‌n‌e‌s‌s o‌f b‌o‌t‌h m‌e‌t‌h‌o‌d‌s c‌a‌n h‌a‌n‌d‌l‌e t‌h‌e c‌o‌m‌p‌l‌e‌x‌i‌t‌y o‌f n‌u‌m‌e‌r‌i‌c‌a‌l i‌n‌t‌e‌g‌r‌a‌t‌i‌o‌n m‌e‌t‌h‌o‌d‌s f‌o‌r o‌t‌h‌e‌r t‌y‌p‌e‌s o‌f i‌n‌t‌e‌g‌r‌a‌t‌i‌o‌n m‌e‌t‌h‌o‌d (e‌x‌p‌l‌i‌c‌i‌t) n‌a‌m‌e‌d. A‌s a r‌e‌s‌u‌l‌t, t‌h‌e c‌u‌r‌r‌e‌n‌t r‌e‌s‌e‌a‌r‌c‌h c‌o‌n‌f‌i‌r‌m‌s t‌h‌a‌t, a‌s c‌o‌m‌p‌l‌i‌c‌a‌t‌e‌d a‌s t‌h‌e C‌l‌o‌s‌e‌s‌t P‌o‌i‌n‌t P‌r‌o‌j‌e‌c‌t‌i‌o‌n M‌e‌t‌h‌o‌d i‌s, i‌t r‌e‌m‌a‌i‌n‌s s‌t‌r‌o‌n‌g‌l‌y s‌t‌a‌b‌l‌e i‌n o‌r‌d‌e‌r t‌o i‌n‌t‌e‌g‌r‌a‌t‌e e‌q‌u‌a‌t‌i‌o‌n‌s u‌n‌d‌e‌r c‌o‌n‌d‌i‌t‌i‌o‌n‌s o‌f l‌a‌r‌g‌e s‌t‌r‌a‌i‌n a‌n‌d d‌i‌s‌p‌l‌a‌c‌e‌m‌e‌n‌t, s‌u‌c‌h a‌s t‌h‌e l‌i‌q‌u‌e‌f‌a‌c‌t‌i‌o‌n p‌h‌e‌n‌o‌m‌e‌n‌o‌n. O‌n t‌h‌e o‌t‌h‌e‌r h‌a‌n‌d, c‌o‌m‌p‌a‌r‌e‌d w‌i‌t‌h t‌h‌e C‌l‌o‌s‌e‌s‌t P‌o‌i‌n‌t P‌r‌o‌j‌e‌c‌t‌i‌o‌n M‌e‌t‌h‌o‌d, t‌h‌e C‌u‌t‌t‌i‌n‌g P‌l‌a‌n‌e M‌e‌t‌h‌o‌d i‌s n‌o‌t o‌n‌l‌y m‌o‌r‌e p‌r‌e‌c‌i‌s‌e a‌n‌d a‌c‌c‌u‌r‌a‌t‌e, b‌u‌t a‌l‌s‌o m‌u‌c‌h f‌a‌s‌t‌e‌r. A‌d‌d‌i‌t‌i‌o‌n‌a‌l‌l‌y, t‌h‌e C‌u‌t‌t‌i‌n‌g P‌l‌a‌n‌e M‌e‌t‌h‌o‌d b‌e‌n‌e‌f‌i‌t‌s f‌r‌o‌m a‌n u‌n‌d‌e‌n‌i‌a‌b‌l‌e s‌i‌m‌p‌l‌i‌c‌i‌t‌y a‌g‌a‌i‌n‌s‌t t‌h‌e C‌l‌o‌s‌e‌s‌t P‌o‌i‌n‌t P‌r‌o‌j‌e‌c‌t‌i‌o‌n M‌e‌t‌h‌o‌d. S‌o‌m‌e‌w‌h‌a‌t i‌m‌p‌o‌r‌t‌a‌n‌t‌l‌y, t‌h‌i‌s s‌t‌u‌d‌y a‌i‌m‌s, b‌y p‌r‌e‌s‌e‌n‌t‌a‌t‌i‌o‌n o‌f b‌o‌t‌h t‌h‌e s‌t‌r‌o‌n‌g a‌n‌d w‌e‌a‌k p‌o‌i‌n‌t‌s o‌f e‌a‌c‌h m‌e‌t‌h‌o‌d s‌i‌m‌u‌l‌t‌a‌n‌e‌o‌u‌s‌l‌y, t‌o a‌i‌d r‌e‌s‌e‌a‌r‌c‌h‌e‌r‌s i‌n s‌e‌l‌e‌c‌t‌i‌n‌g a r‌e‌a‌s‌o‌n‌a‌b‌l‌e m‌e‌t‌h‌o‌d, w‌i‌t‌h r‌e‌g‌a‌r‌d t‌o s‌p‌e‌c‌i‌a‌l c‌o‌n‌d‌i‌t‌i‌o‌n‌s a‌n‌d t‌h‌e l‌i‌m‌i‌t‌a‌t‌i‌o‌n‌s o‌f e‌a‌c‌h p‌r‌o‌b‌l‌e‌m.

In this paper, different amplification patterns of 2-D semi-sine shaped valleys and their surroundings subjected to vertically propagating incident out-of-plane SH waves are presented. The half-plane time domain BEM approach proposed by the authors was used to obtain the results. Compared to the previous studies on boundary elements, avoiding a wide range of ground surface meshing and focusing the elements only on the valley surface were the obvious distinctions of the present study. In this regard, effects of key parameters such as shape ratio of the valley and wavelength of incident waves were considered. Evaluation of the results indicated significant influence of the mentioned parameters on the valley surface behavior. Also, the amplification potential of semi-sine shaped valley under vertically out-of-plane SH wave had a higher amplitude than in-plane SV wave. The obtained results can be used for seismic micro-zonation discussion in order to correct and complete the existing studies.

A series of microtremor array measurement was performed in a site of Tehran (shaghayeg park) with the aim of estimating the shear wave velocity (Vs) profile for near surface layers. The SPAC and f-k array processing technique were used and the results were compared with other information specially a 200 meters depth borehole and the down-hole and PS logging data have been done in this paper. The data of different time, day and night were processed and the results were compared with the actual Vs profile by definition the various criteria. We found that, the SPAC method is probably more convenient compared to the f-k method. SPAC method gives results as good as the f-k method while using smaller number of recording stations and shorter array dimensions.

There are many parameters that influence the dynamic response of structures in contact with fluid medium. One of these parameters is the direct effect of reservoir، especially for high structures during severe earthquakes، so there are an extensive amount of publications about the analysis of fluid-structure interaction systems in different engineering branches. In this research، studies in the field of civil engineering with an emphasis on dams will be considered. The different methods of analysis of the fluid-structure interaction problems are reviewed and then some case studies for structures such as retaining walls، concrete، CFR and embankment dams، are discussed. Due to the development of numerical methods in recent years، the studies done using such methods are considered with more emphasis. However، analytical methods such as Westergard and Chopra cases are presented and discussed in this paper. Studies in the field of concrete dams are presented in two divisions as modeling approaches and boundary condition effects. Then the studies about the seismic interaction of reservoir-CFR dams are presented in the related section. Also analysis of seismic coupled reservoir-structure systems for a concrete dam and a CFR dam، which have been conducted by the authors with ADINA software، are presented and compared with the results of the previous studies. This comparison shows the accuracy of the results of ADINA software in the field of dynamic coupling of water-structure systems for concrete and CFR dams. Finally، the previous studies for the dynamic interaction of embankment dam-reservoir system are presented and the related results are discussed. It is concluded from reviewing the previous study that the amount of hydrodynamic force in the fluid domain is a function of the frequency content of incident seismic wave and the ratio of the natural frequency of dam to reservoir one. Therefore، there is not a certain height restriction for unconsidering the effect of interaction of reservoir-dam. Also، if the frequency content of energy of seismic wave is less than the natural frequency of reservoir، the effect of considering the coupled water-structure system would be less. Consequently، the final results of such system would be less affected by the reservoir. As another result، if the ratio of the natural frequency of reservoir to dam is almost «2»، the interaction of reservoir-structure has no considerable effect on the final seismic response of coupled system. In the special case of CFR and embankment dams، there are fewer researches in comparison with concrete dams. The main reason can be related to the low slope of upstream face of the dam which reduces the hydrodynamic force of the reservoir. But there are not sufficient available researches that improve the accuracy of such arguments in many different conditions of incident wave (magnitude of PGA، the frequency content of seismic wave، spatial ground motion condition)، and variation of some parameters such as per- meability coefficient of shell materials، height of dam، and slope of upstream face. Therefore، it seems that in the future، more studies should be done in the field of embankment dam-reservoir coupled system.

There are different methods for seismic analysis of topographic features which include analytical، semi-analytical and numerical methods. In the analytical methods extracted from matched asymptotic expansion of wave and Bessel/Hankel functions، responses are presented in terms of summation limit as closed-form solutions. Based on the semi-analytical methods، the problem is decomposed into two primary and secondary parts، which can be solved analytically and numerically. According to what is observed in the nature، the responses of analytical or semi-analytical methods have high accuracy، various types of arbitrarily shaped topographic features cannot be applied for modeling in reality. It results in the development of numerical methods which have good flexibility. These methods can be divided into three types including volumetric، boundary and mixed methods، This paper presented the most important studies that have been conducted in the past half-century (1960-2011) on the mentioned topics. The above mentioned studies are classified based on the used methods، prepared model type and publication year. Despite the development of volumetric methods، such as finite element method (FEM) or finite difference method (FDM) and their simple formulations، the whole body including the inside and boundaries must be discretized in order to model the topography features. This process requires too much time and data. As a result، special attention has been given to the Boundary Element Method (BEM) among the various existing numerical methods during the recent two decades. In this method، only the boundaries of the media need to be discretized in order to analyze an elastic continuous media. Two BEM formulations have been proposed to be used in modeling، including full-plane and half-plane. First، the formulas are classified and the governing boundary integral equations are presented. Then، the related studies based on the full-plane and half-plane fundamental solutions are reviewed. It is worth mentioning that out-of-the-plane wave (SH wave) has been considered as the case study in all studies investigated in this paper.

It is well established that the seismic ground response of surface topographies may differ from those of free field motion during earthquakes. Complex nature of seismic wave scattering by topographical structures can only be solved accurately and economically using advanced numerical methods under realistic conditions. Among the numerical methods, the boundary element is a powerful numerical technique for analyses of linear and homogeneous materials for both bounded and unbounded domains. In this paper, the algorithm of seismic wave scattering by homogeneous media using time-domain three-dimensional boundary element method has been presented. Three-dimensional traction elastodynamic kernels for both cases of constant and linear variation of displacement have been presented. The convoluted kernel for constant time variation contains apparent singularities in the wave fronts, while in the linear time-convoluted elastodynamic traction kernel, apparent singularities in the wave's front disappear and a well-behaved kernel is resulted. Behavior of the constant and linear time-convoluted elastodynamic traction kernel have been investigated numerically. Kernel values were calculated at the central point of the three boundary elements considering different time steps. The boundary elements are in different condition of symmetry with respect to the source point. The kernel values in the case of constant time-convoluted elastodynamic traction kernel tend to the elatstostatic fundamental solution as expected, Whereas the kernel values in the case of linear time-convoluted elastodynamic traction kernel is equal to the elastostatic fundamental solution if the time step would be greater than time required to shear waves passed the receiver point on the element. Presented constant and linear time-convoluted elastodynamic traction kernels are casaul and have time-translation property which could be used for optimization of numerical algoritms. The presented elastodynamic kernels have been used instead of temporal integration for wave scattering analyses of homogeneous medium using BE algorithm. Seismic wave scattering by a semi-spherical canyon subjected to incident compressional and shear waves has been analyzed. The semi-spherical canyon has a radius of 200m, shear wave velocity of 800m/s, Poisson’s ratio of 0.25, and mass density of 2.00gr/cm3. The incident wave of the Ricker type has the predominant frequency of 3.0Hz. Calculated results in time-domain are presented as well as comparison of results with other transformed-domain methods in term of dimensionless frequency, which shows the efficiency of the presented boundary element algorithm for solution of seismic wave scattering by homogeneous media in time domain as well as the accuracy of elastodynamic kernels.

Studying the seismic behavior of earth dams is one of the most important problems in the geotechnical science. Using weak recorded responses on dam body is the most appropriate method in studying seismic behavior of dams. Available accelerograms on Masjed Soleiman dam body is a powerful tool to reach to this aim. Using recorded accelerograms in the gallery station as the input motion and also using different masses for foundation, 2D numerical analysis are performed and the dam-foundation interaction problem is studied. Recorded and calculated responses of dam body are compared with each other based on different approaches. It should be mentioned that the used earthquake records in this research are weak and linear behavior for dam body is assumed. The obtained results show that time-frequency distribution (TFD) is an appropriate method to process the recorded and calculated signals and also using below 50 per cent (20-30 per cent) for the mass of foundation is can lead to the nearest results to recorded responses.