Soil Dynamics and Earthquake Engineering

Five embankment dams with the height over 100m experienced the May 12, 2008 Wenchuan earthquake with a magnitude of Ms 8.0. Damages to the Bikou loam-core-wall earth-rockfill dam and especially to the Zipingpu concrete face rockfill dam (CFRD) were induced by the great earthquake, despite no significant damages to the other three dams. The Zipingpu CFRD with the maximum dam height of 156m is the highest embankment dam located in the high seismic intensity region during the Wenchuan earthquake and is also the first CFRD experiencing strong shallow earthquake of IX–X degrees in the world. In this paper, the engineering properties, earthquake-induced damages and monitoring results of the Zipingpu CFRD are described in details. Its aseismic characteristics are analyzed from the following aspects: 1) basic features of earthquake damages, 2) deformation characteristics, 3) evaluation of earthquake damages, 4) aseismic performance, 5) ground motion, 6) weak parts of seismic resistance, and 7) repairability performance. A brief introduction to the damage to the Bikou dam is also made. These are expected to be beneficial to the understanding of the seismic behavior of high embankment dams subjected to strong earthquakes.

In this paper, a simplified analytical method was developed for the axial harmonic response of partially embedded pile groups in layered soil. Based on pile-to—pile interaction factors, transfer matrix method was used to setup the dynamic model of partially embedded pile groups. A comprehensive parameter study focused on the influence of length ratio(L₁/L₂), pile spacing(s/d) and vibration frequency(f) on the dynamic response of pile groups, and following conclusions could be got: (1) the increase of length ratio(L₁/L₂) would reduce vertical dynamic impedance of single and pile groups; (2) the pile-pile interaction factors vary with the pile spacing and vibration frequency, and will be seriously weaken for length ratio (L₁/L₂); (3) the length ration (L₁/L₂) has evident influence on dynamic response of pile foundations with the rise of vibration frequency.

This article has accomplished the model test for 1:20 loess slope, investigated the law of similitude, boundary condition treatment and so on in the model test, studied the change rules of dynamic properties and dynamic response rules for loess slope in dynamic compaction. Results show that the amplitude of dynamic response for loess slope in dynamic compaction fades out rapidly with the impact loading effect; the vibration cycle is less than 1s and the major frequency is between 25~45 Hz that no superimposed vibration will occur. The amplification effect on radial acceleration is more obvious for loess slope in dynamic compaction, the vertical vibration prevails at lower part of slope while radial vibration prevails at upper part of slope. There is amplification effect for response amplitude on impact vibration of on the ridge of loess slope. There is obvious amplification effect on slope for input acceleration along the slope, especially the most obvious amplification effect at the top of slope. The test results have favorable influence on revealing the rules of dynamic response for loess slope in dynamic compaction, and provide instructive reference for the engineering design and construction for the loess region.

Horizontal vibration tests are performed on reinforced concrete single pile (L/d = 20) and group piles (L/d = 20 and s/d = 2, 3, 4) under varying levels of harmonic excitation acting above the center of gravity of the pile cap-loading system. The observed response curves display marked nonlinearity as the natural frequencies decreases with increasing intensity of excitation for both horizontal and rocking mode of vibrations. The measured response is compared with linear elastic and nonlinear solutions of Novak's continuum approach. To account for the nonlinear response of the piles, provisions are made for yielding of soil around the piles by introducing the weak boundary zone concept. Different separation length between the pile and top soil is also considered for different excitation intensities in the nonlinear analysis. It is found that a close agreement can be achieved between theoretical predictions and measured response curves by allowing for boundary zone and separation between pile and soil. It is also found that the boundary zone parameters, pile-soil separation, pile-soil-pile interaction and the embedded effect of the pile cap play a major role in the coupled dynamic response of pile foundation.

In order to insure the safety of pile groups on the inclined soils in the earthquake prone area, analysis of seismic performances of pile groups in the inclined soil layers is of prime importance. Centrifuge tests of 50g and responding numerical simulations are conducted to investigate the seismic performances of pile foundation under strong ground shaking conditions. Moreover, detailed discussions and comparisons between numerical modeling and centrifuge tests are included. These centrifuge test model consisted of a model pile foundation of 2 x 2, 10 times diameter spacing on an inclined dry or saturated layer of slope angle = arctg(l/2). Effective stress analysis method based on a multiple shear mechanism is employed for conducting the numerical predictions and validation. It is concluded that the measured and computed responses of acceleration, displacement are in good agreement. The physical and numerical models both indicate that the lateral displacements of pile groups are much larger in laterally spreading soils than in dry soils. The dynamic centrifuge test and the numerical simulation method proposed in this paper is reliable and applicable for analyzing seismic performance of soil-pile system in inclined soils subjected to strong motions.

Based on Biot's wave equation, the dynamic response of a transversely isotropic saturated soil under train load was studied with Fourier transform technique. In this application, the track, including the rails, rail pad, sleepers and ballast, is modeled as an infinite layered beam structure. Analytical solutions for displacement, stress and pore pressure are derived in the form of integral. Numerical results are obtained by using the inverse Fourier transform and are used to analyze the influence of the anisotropic parameter of the ground on the ground vibration and pore pressure. It is shown that the anisotropy of stratum has great influence on the behavior of soil-track system.

The dynamic analysis and design for a large pump foundation are investigated with different design options. The nonlinearity of soil is considered approximately using the boundary zone model with non-reflective interface. The impedances (stiffness and damping) and the dynamic response of foundation are generated from a computer program DYNAN. The amplitudes calculated might be larger than the allowable vibration limit, if the design of foundation is not reasonable. Three options of the foundation design are considered: shallow block foundation, deep block foundation, and cast-in-place concrete piled foundation. The stiffness and damping of foundation, dynamic response, and construction cost are compared with the different types of foundation. The ground water is very shallow in the construction site, and the level of water even closes to the surface. The effects of groundwater on dynamic response of foundation are discussed.

Based on laboratory study, cumulative effect of soil nailing under cyclic load is studied. The cyclic load is produced by a multi-channel load system, from experimental results, displacement of facing increases considerably after a certain load number, then keep almost constant, which indicates attenuation of accumulation effect. Thereafter, in order to compare with laboratory results, through ADINA system, based on Mohr-Coulomb criteria, a plain strain finite element model(FEM) is built. From both experimental and calculation results, considering different stiffness and boundary constraints at the bottom of facing, displament of facing is smaller with concrete facing(greater stiffness), which is than with wood facing(smaller stiffness), similarly, displacement of facing is smaller with fixed bottom than with free one, moreover, load frequency has pronounced influence on displacement of facing.

Soil-structure interactions are important for the safety of the underground structures under earthquake loads. In this paper, model tests were conducted on 1/60 scaled model of the prototype Xi'an metro tunnel. The seismic response data including the acceleration, the displacement and the dynamic soil pressure between the tunnel and soil were measured by testing the scaled model on a shaking table. From the test result, it is concluded that 1) the effects of tunnel and soil interactions are important for the bulk dynamic responses; 2) the soil pressure and the acceleration changed with the seismic inputs. The soil pressure at the top of the tunnel increased while the pressure at the bottom decreased; 3) the acceleration of the tunnel is greater than the adjacent soils.

The effect of soil flexibility is generally ignored in seismic design of buildings. The design is generally carried out based on the results of dynamic analysis considering fixed base condition. Flexibility of soil causes lengthening of lateral natural periods due to overall decrease in lateral stiffness. Such lengthening may considerably alter the seismic response of the building frames. It is therefore, necessary that the dynamic inter relationship between soil and structure to be taken into account in the seismic analysis of structures. In order to evaluate the seismic response of a structure, at a given site, the dynamic properties of the combined soil structure system must be established. Due to the differences in responses of a rigidly supported structure and elastically supported structure, it is essential to study the effect of soil flexibility on structure for safety and economy. The seismic load acts during a very small interval of time. Hence, during the action of such loads, instead of consolidation settlement, the instantaneous settlement is expected to occur. This behavior of soil can be conveniently simulated using a set of elastic springs. This study has been carried out for numerous building frames resting on strip foundations and comparison between the nature of change in lateral natural periods and base shears due to the incorporation of soil flexibility relative to that at fixed base condition has been presented. Such study may help to provide guidance to assist more accurately the seismic vulnerability of the building frames resting on strip foundations and may be useful for seismic design.

The ever expanding world trade necessitates larger container ships and increases the demand for sea transports. However, the increasing occurrence of shipping accidents, such as ships running aground, threaten the safety of freights and ships. Due to the complex contact mechanisms between ships and structures or the ground, it is very difficult to predict the collisional force and stopping distance when applying classical mechanical theory. In the related project `Hochdonn' of BAW (Federal Waterways Engineering and Research Institute, Germany) collision experiments were performed to analyze the impact mechanisms in grounding problems. This paper describes the simulation of the collision of the ship "Gerda" with a sandbank using a coupled Eulerian-Lagrangian (CEL) method. Numerical analysis were conducted and compared with the experimental results.

This study presents a simplified method to conduct the behavior of pile foundations due to lateral spreading. Wave equation analysis applied to model the pile behavior under seismic motions. According to the concept of force-based method, the authors suggest to adopt the dynamic earth pressure in the wave equation analysis. Numerical procedures were validated with the well-documented cases of damaged piles in 1995 Kobe earthquake. In the meantime, comparing the numerical results with the case histories, one can again evaluate the damaged features of piles and distinguish the actual failure pattern of piles. The predictions and the observations were found in good correspondences.

The dynamic analyses of the landfill slopes were carried out on typical landfills (Bishkek) in Kyrgyzstan. The site investigation consists of boreholes, geotechnical laboratory tests and geophysical tests in field. Based on the results of the site investigation, dynamic analyses of the selected landfills were carried out with the finite-difference program FLAC3D and QUAKE/W Features, advantages and disadvantages of these programs are discussed and the results of the response analysis of the selected landfills, subjected to an earthquake with a peak ground acceleration of 0.5g, are presented in this paper. The results of the analysis showed that the slope instabilities will occur approximately after 12 seconds of shaking.

In recent years, damage to embankments from earthquakes has been frequently reported. In this paper, the deformation and failure behavior of an embankment constructed on a weak clay foundation during and after an earthquake is investigated using numerical analysis, GEOASIA, assuming a 40 g centrifugal field. The main conclusions obtained were as follows. 1) Although the embankment remained stable without large deformation during the earthquake, a slip plane subsequently penetrated through the embankment, resulting in delayed failure (circular arc slip). 2) The deformation behavior (failure mode) of the foundation and embankment varies greatly depending on the characteristics of the incident seismic motions.

During earthquakes, the materials of earthfill dams undergo significant changes in their properties. These modified properties of the soil affect the stability of the dam. The most severe situation is dam failure due to liquefaction of the granular soils in the shoulders. The development of liquefaction is directly related to the excess porewater pressure that would develop during earthquake shaking. The generation and dissipation of excess porewater pressure is a phenomenon that depends on the drainage possibility and length of drainage path. Therefore, with some modifications on the slope of the dam, the clay core can assume different arrangements. These arrangements modify the seismic response of the dam. Numerical codes are useful tools to investigate the safety of dams in seismic prone areas. In this paper FLAC3D numerical tool is used. The influence of the arrangement of the clay cores of the dam on the development of porewater pressure and crest settlement of earthen dams, and hence seismic performance of earthen dams is investigated. Based on the numerical investigations, the performance of earthfill dams increases with increase in the angle of inclination of the center line of the core from the vertical towards the upstream. So the arrangements of the clay core for dams in seismic areas can be taken as one design criteria during earthfill dam design.

The Noto Hanto Earthquake in 2007 caused large-scale landslide of 11 embankments in NOTO YURYO road, especially the embankment on inclined ground. In order to clarify the cause of the large-scale landslide of embankment, the laboratory tests on the embankment material, the weathering tuff and the seismic response analysis of the embankment on inclined and horizontal grounds by the static/dynamic soil-water coupled finite deformation analysis code, GEOASIA. The essential results and conclusions are follows; 1) The unconfined strength dramatically decreases by absorbing water beyond the optimum water content. 2) The landslide of the embankment on inclined ground is caused by migration of porewater during/after the earthquake. The soil element of landslide swells both elastically and plastically with structure upgradation and loss of overconsolidation after the earthquake. 3)The embankment on the horizontal ground does not slide but move a little. The soil element did not swell but consolidate after the earthquake due to the generation of the positive porewater pressure in the center of the embankment during the earthquake.

Severe damages of river dikes caused by liquefaction have been often observed. In previous earthquakes, it has been reported that many river dikes were deformed by the liquefaction during earthquake. The river dike in the middle region of Shinano River is built on the loosely deposited sandy layers. Therefore, a large deformation of the river dike by the liquefaction is expected. It is very important to understand the deformation mechanism of the river dike by liquefaction in order to prevent a future damage of river dike along Shinano River. In this study, effective stress based finite element analyses were carried out by the program code "LIQCA" to reproduce the past damage and to compare the damage of the river dike by different earthquake motions. Three earthquake motions by the 1964 Niigata earthquake, the 2004 Niigataken Chuetsu earthquake and the 2007 Niigataken Chuetsu-Oki earthquake had different duration time and acceleration amplitude. The comparisons among damages by three earthquakes were carried out. As the results, it was confirmed that the duration time and the acceleration amplitude of earthquake motion were key factors which affect the damage of the river dike.

Generally, in order to evaluate the seismic demand of structures, it is assumed that the structure is located on a rigid soil, with increasing the soil flexibility, there will be significant variations in the structural response, i.e. the effects of Soil-Structure Interaction (SSI). Additionally, ground motions close to active faults have some important characteristics that make them to be different from those recorded in far-fault regions. Forward rupture-directivity velocity pulses, high-frequency acceleration records, and permanent displacement, are notable specifications of records close to ruptured faults. Among mentioned characteristics, forward rupture-directivity effect causes velocity pulses that could potentially exert great damages to buildings in near-fault regions. These pulses possess statistical certainty; hence, researchers tried to present synthetic models for them. In this paper, a parametric study is carried out on the elastic response of soil-structure systems having shallow foundations subjected to a pulse-type motion and near-fault records in order to develop a systematic procedure for assessing near-fault and SSI effects on design of structures. It is concluded that under SSI effects there are clear similarities between elastic demands subjected to pulse-type, and near-fault motions. Consequently, the final form of relationship as a representation of near-fault characterizations under SSI effects is presented.

Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, the bridge stiffness is also measurably increased in the winter months. Significant changes in the bridge pier boundary conditions due to seasonal freezing requires additional detailing to ensure a ductile performance of the bridge during the design earthquake event. This paper reports the latest results obtained from a project aimed at systematically investigating the effects of seasonal freezing on the seismic behavior of highway bridges in cold regions. Presented here are the results obtained from numerical simulation of the overall dynamic performance and field monitoring study of the bridge selected for study in this project. By using OpenSees computational platform, a three-dimensional FE model of the bridge foundation is established to investigate the impact of seasonal frost on the bridge substructure behavior. In the meantime, a bridge is instrumented with a network of accelerometers to monitor its dynamic and seismic behavior. Earthquake-induced vibration data have been collected and analyzed. The results show that seasonal frost has significant impact on the overall dynamic behavior of bridges supported by pile foundations in cold regions, and these effects should be accounted for in seismic design.

Limited space in urban area makes it attractive to reuse the existing foundation. This paper presents a case study on the use of seismic piezocone penetrometer (SCPTu) to conduct parallel seismic test for the determination of the length of unknown foundation. The tip resistance and side friction by cone penetrometer provide the distribution of mechanical properties of the underground layer. The geophones in seismic piezocone tip acts as seismic wave receiver for parallel seismic test that is commonly used to determine the length of unknown foundation. By fusion of both information, the capacity of pile foundation under existing building can be determined. This testing procedure is very attractive for reuse of existing foundations. A case study is provided on the use of SCPTu in a building expansion project.

Effects of different kinds of damping and dynamic soil mass on horizontal and vertical footing vibration, e.g. dynamic stiffness and footing mass, have been analyzed. Total damping should include material damping and geometrical damping. Material damping tends to reduce the dynamic stiffness of the footing. Dynamic soil mass and the effect of footing mass with respect to the geometrical damping have been considered in the vibration analyses. Expressions for total mass, total damping and total dynamic stiffness of the system for horizontal and vertical vibration have been presented in this paper for use in these analyses. The differential equation for evaluation of these effects and some important circular frequencies for horizontal vibration of a rigid footing on an elastic half space are discussed. The newly presented expressions for total mass, total damping and total dynamic stiffness could be used to calculate whether permanent displacement or resonant frequency and the maximum amplitude of vibration will occur.

A computational approach based on pile-soil dynamic interactions was developed to analyze ground response due to excitation on pile foundation. In this work, pile group was assumed to have the concentric arrangement. The geometric and material properties of piles and soils were assumed to be invariable along the azimuth angle by introducing the equivalent stiffness of grouped piles. An axisymmetric finite-element model was employed after taking the Fourier expansion in azimuth for computational convenience. The field test of ground vibration in the vicinity of pile foundation which was subjected to horizontal loading by a shaker at the top of the footing was used to verify the proposed approach. The comparison of the simulated results and the field recorded data showed good agreement. This proved the reliability of the axisymmetric three-dimensional finite element program to predict the field vibrations considering pile-soil interactions.

Test results of Toyoura sand subjected to plane strain cyclic loading illustrates that it has the memory effect i.e., memory about its last load reversal point in the shear stress-strain plane, which produces a closed hysteretic loop. To simulate this response, a novel formulation of kinematic hardening rule is used here by introducing a framework in which the dimensionless kinematic hardening rate is varied according to the instantaneous stress value at that point along the stress path. When the direction of the loading is reversed, the initial rate of hardening is restored and the rate of variation of hardening is scaled according to extended Masing's law. As a result, a closed hysteretic stress-strain loop is obtained due to cyclic loading. Finally, cyclic plane strain response of Toyoura sand is simulated and compared with available test results.

Deformation characteristics of marine sedimentary, which is widely distributed in Ningbo area, are important for the construction of pavement-subgrade system, rail transit-subgrade system, dynamic foundation, and so on. In this paper, FlowTrac II system, a fully automatic bidirectional excitation triaxial testing system produced by GEOCOMP, is used to study the deformation characteristics and the dynamic responses of subgrade in the area covered by rail transit network of Ningbo city. A series of unidirectional cyclic triaxial tests are conducted on remoulded mucky soil samples. Effects of amplitude of dynamic stress, consolidated confining pressure and load repetition on the behaviors of the saturated mucky soil are analyzed. It is shown that the influence of the above factors on the dynamic elastic modulus, damping ratio is great. At last, the envelopes of dynamic shear modulus ratio G/G_max versus dynamic strain D for mucky soil are presented.

In this paper, the potential of relevance vector machines (RVM) based classification approach has been used to assess the liquefaction potential from actual shear wave velocity data. RVM is based on a Bayesian formulation of a linear model with an appropriate prior that results in a sparse representation. As a consequence, it can generalize well and provide inferences at low computational cost. It also gives probabilistic output through Bayesian inference. Input parameters of RVM model are effective vertical stress (σ'_vo), peak acceleration at the ground surface (a_max), earthquake magnitude (M), shear wave velocity (V_s), and soil type. In this study, Gaussian functions are used as kernel for RVM model. The results show that the RVM model predicts liquefaction with accuracy of 98.21%. The developed RVM model provides a viable tool to earthquake engineers in assessing the sites susceptible to liquefaction.

The co- and postseismic behaviors of typical loose sandy ground and soft clayey ground improved by the sand compaction pile (SCP) method were investigated using a soil-water coupled finite element deformation analysis program incorporating the SYS-Cam clay model. The results indicated that the deformation caused by earthquakes was suppressed in the SCP improved grounds, irrespective of whether they were sandy or clayey. Although the surrounding ground was liquefied in the case of SCP-improved sandy ground, the confining pressure was maintained in the SCP interpile zone because of the compaction effect produced by the cavity expansion of the sand piles. In the case of the SCP-improved clayey ground, negative excess pore pressures appeared in the SCP sand piles because of the hardening that results from plastic expansion and stress was concentrated on them.

The Ground Penetrating Radar (GPR), which is an effective, speedy, continuous and non-destructive testing equipment, its application in pavement has been the international hot subject since 1980s. This paper introduces the basic theory of Finite Difference Time Domain (FDTD) by analyzing the characteristics of electromagnetic wave propagation in pavement, especially from 1-dimension FDTD equation, soft source, effective parameter of layered boundary and Absorbing Boundary Condition (ABC), which have the greatest significance in FDTD simulation of GPR. Then a forward air coupling GPR propagating in layered medium model is established. Moreover, the validity of this forward model is examined through several simulated and actual cases with the maximum error one of 2%. This model develops a new concept for practical and accurate interpretation of GPR reflection data, which can develop a new algorithm to calculate the thickness of pavement's layer, and even develop a new way to measure the moisture and density of pavement's layer in non-destructive testing.

The aim of the present study is to investigate the cyclic shear behavior of clay, in particular the simple shear conditions. In general, cyclic triaxial tests are performed to evaluate the deformation and the strength characteristics of clay. However, the direction of cyclic loading in triaxial tests is different from the direction of cyclic shear loading in the natural ground. In the present study, therefore, a cyclic simple shear test apparatus has been newly developed and various cases of cyclic simple shear tests have been performed using reconstituted clay and intact natural clay. From the test results, the cyclic shear behavior of clay, which is useful for constitutive modeling, could be precisely obtained. Furthermore, it has been found that the cyclic shear strength of clay can be determined with only the vertical effective stress.

A study of the effect of cyclic loading frequency on the dynamic properties of saturated soft marine clay was presented. The research was based on a series of stress-controlled undrained one-way loading cyclic triaxial tests conducted on normally consolidate undisturbed Tianjin soft marine clay. It is found that accumulative axial strain and normalized average pore pressure with number of cycles are strongly affected by cyclic frequency, but the effect of frequency on normalized average pore pressure with accumulative axial strain is not significant, and the frequency is also a less important factor that affects degradation index with number of cycles. Accumulative axial strain, normalized average pore pressure and degradation index with number of cycles were successfully modeled by hyperbolic line, while normalized average pore pressure with accumulative axial strain can be modeled by Hill growth line. These models can be used to estimate the dynamic properties of soft clay under cyclic load reasonably.

This paper concerns analysis of the free field response of partially saturated soils to cyclic loading, with a particular attention on liquefaction. Analysis is conducted using a numerical model elaborated for the liquefaction of partially saturated soils together with a cyclic elastoplastic constitutive relation implemented in a finite element program. The paper presents firstly the numerical model, and then the influence of the soil saturation on the free field response for different positions of the water table. Analyses show that the soil saturation degree largely affects the free field response to seismic loading. The decrease in the soil saturation leads to a decrease in the rate of generation of the excess pore-water pressure and consequently to a reduction in the liquefaction risk.

The paper deals with the problem of dynamic consolidation of two-phase soil medium. Finite Element approach is used to calculate tangential stresses and pore pressure and what follows to describe the wave propagation. Biot's formulation, with so called u - p simplification and Pastor — Zienkiewicz Mark III constitutive relation, is implemented. This model, which treats the soil as an inelastic skeleton saturated with a pore fluid is very close to real behavior of non-cohesive soil under dynamic excitation. Numerical analysis mentioned, is used not only to obtain the result but also to assess them. Cohesion, friction angle and other geotechnical parameters are taken from laboratory tests. Different records of real vibrations along with artificial impulse wave is applied as dynamic loading. Constitutive relations are fully nonlinear and depend on soil type. From numerical calculation we obtain the diagonal shear stress bands which form the typical crosses and pore pressure which responds even after fade of input, proving liquefaction phenomena. The signal processing tool such as Fourier and wavelet transform is used to analyze the results. Two important information such as the time when dominant frequency is reached and the frequencies which are filtered, are retrieved only from wavelet analysis.

To design for offshore pile foundations, it is necessary to account for the degradation of stiffness and strength of saturated soft clay under long-term cyclic loading. Hence using the laboratory GDS test apparatus, a series of static and cyclic undrained triaxial tests were conducted on isotropically and anisotropically consolidated natural undisturbed saturated soft clay with the shear wave measured by bender element system during cyclic loading. The experimental results show that under the same consolidated condition the undrained strength and stiffness of soft clay markedly reduce with the increase of the cyclic stress ratio and the progressive number of cycles. On the other hand, anisotropic consolidation and lower effective consolidation pressure decelerate the degradation of stiffness under the same cyclic stress ratio. The dynamic deviatoric stress level was introduced considering the effects of effective confining pressure, consolidated static deviatoric stress and dynamic deviatoric stress. The dynamic deviatoric stress level is further used to describe the reduction of stiffness and strength of saturated soft clay under cyclic loading.

To simulate the effects of fines content on the liquefaction properties of sand, specimens of different fines content were prepared. Based on cyclic triaxial compression tests of these samples, the effects of fines content on the liquefaction properties were analyzed. Results show that for a constant value of dry density, the liquefaction resistance decreases with increasing fines content. Beyond the critical value of fines content of 30% the trend is reversed and the liquefaction resistance increases with increasing fines content. The results are consistent with the variation of relative density with increasing fines content, which verifies the effects of non-plastic fine-grained soils on liquefaction resistance of sandy soil reported by Polito et al. (2001).

A series of flume experiments under static and dynamic conditions were conducted to study the Xiejiadian rock avalanche, which was triggered by Wenchuan Earthquake in China. Six influencing factors acting on the run-out of rock avalanches were investigated by releasing three granular materials in a designed flume. Test results under static conditions showed that the coarser sample was of higher fluidity than other types with excessive content of finer particles. Positive correlations were obtained between the following parameters: the angle of flume and the run-out of deposit; the angle and the accumulation of deposit; the mass and the run-out; the mass and the accumulation. In the case of consecutive releases, the traveling length of entire volume was affected mainly by the first release, while subsequent releases only had effects on the height and weight of the main part deposit. The roughness of bottom surface of the flume had a large effect on the finer particles than coarser particles. The run-out of deposit decreased when obstacles were introduced. Dynamic results showed that shaking force has a significant effect on the increase of run-out distance of the deposit compared with results under static. The run-out distance increased with the increase of acceleration amplitudes. Whereas, the run-out distance reduced gradually with the increase of frequency.

This paper discusses the use of the passive horizontal-to-vertical spectral ratio (HVSR) ambient noise method for near surface characterisation of the soil layers at a proposed building site. The uniqueness of the HVSR method is in having no need for any external excitation sources and cabling, and the setting up time is also very short. In our study, HVSR measurements were taken at spots interspersing the few available bore logs, with each measurement taking no more than 10 minutes. This allows the entire site to be measured very expeditiously. The HVSR spectra were then inverted by fitting measured to theoretical spectra values to obtain the V_s profile of the underlying soil layers, based on an assumed layered soil model. A side benefit of this approach is that the resonance frequencies of the site were also determined without undertaking additional work. In addition to benchmarking the soil profile inverted from the HVSR measurements against the available bore log data to verify its accuracy and correctness, comparisons have also been made with the results from the MASW and ReMi array-based methods. The study shows that the HVSR method performed very well against these surface wave methods. It is thought that the HVSR technique would be especially cost-effective for characterising a large site in conjunction with a few bore logs.

Compared with natural grounds formed by sedimentation over many years, reclaimed artificial grounds are often weak. In this work, modeling of a reclaimed offshore artificial ground and its seismic response analysis were carried out, and the vulnerability of the weak reclaimed layers to seismic activity is pointed out. This study was carried out using a soil-water coupled finite deformation analysis program GEOASIA incorporating an elasto-plastic constitutive model (the SYS Cam-clay model). This model is capable of describing, within a single framework, the behaviors of sands, clays, and intermediate soils consisting of sand/clay mixtures through their soil skeleton structures (structure, overconsolidation, anisotropy) and its works. In reclaimed sand, lateral flow and upward lifting of lightweight underground structures occur because of liquefaction during an earthquake. In reclaimed clay, long-term settlement, which continues for several years after the earthquake, occurs.

As microzonatin studies, microtremor measurements were carried out in many cities in Iran and the resonant frequency of each station was estimated from the peak at the spectral ratio between the horizontal and vertical component. For many of these stations the thickness of the sedimentary cover was known by conducting boreholes or geophysical investigations, and a clear correlation between the resonance frequency and sediment thickness was observed. Three of these cities are located in the southern part of Iran near the sea (Persian Gulf). We attempted to derive a formula to correlate the frequency of the H/V peaks to the soil profiles properties such as thickness, materials properties and shear wave velocity. In addition, by using all of these microtremor measurements and applying the derived relationship, we tried to estimate the basin shape for these areas.

Many huge structures such as dams, plants and bridges located in canyon sites, are subjected to non-uniform ground motions and so their conventional type of analysis (assuming uniform ground motion) may lead to unreasonable responses. There is noticeable difference between the responses of huge structures to uniform and non-uniform ground motions. In order to conduct non-uniform dynamic analysis of this kind of structures, definition of seismic loading is a main challenge. In this research an efficient algorithm based on the numerical analysis of seismic wave components (P, SH and SV) and their combination is proposed using a single point given accelerogram record of the site. Thus, non-uniform seismic acceleration time series could be generated in different points of the site. Special purpose Boundary element code (TDASC) is developed in order to conduct seismic body waves scattering analysis at a canyon of arbitrary shape. Efficiency of this algorithm has been shown by re-generating the 24 October earthquake free-field accelerograms recorded at the Shafaroud dam site canyon in northern Iran. Comparison of the recorded and generated accelerograms for three different components along the canyon shows a good conformity.

Hybrid Frequency Time Domain (HFTD) method is used to evaluate the nonlinear response analysis of soil layers due to the earthquake incident loads. Solution schemes by the frequency and the time domains are rationally combined to achieve an optimum solution procedure. Fast Fourier Transform (FFT) and Inverse Fast Fourier Transform (IFFT) are used for the transformation of the results from one domain to the other and vice versa. A computer program has been developed to calculate the nonlinear ground response based on HFTD concept. A rational iteration procedure is adopted in which the nonlinear effects are updated in time and depth of the soil layer system and convergence is checked to be within an adopted and predefined tolerance. Shear strength of soil is assumed to follow a nonlinear and hyperbolic relation with shear strains. The method developed here is fast and efficient which guarantees satisfactory results with considerable level of accuracy. Examples are solved and the validity of the results is discussed in the paper.

Historical seismicity data and recent seismic activities in and around Bangladesh indicate that Bangladesh is at high seismic risk. The capital city Dhaka is situated in the seismic Zone 2, which has a basic seismic coefficient of 0.15g. Over the past 40 years, Dhaka city has experienced a rapid growth of urban population. This high population increase demands rapid expansion of the city. Unfortunately, most parts of the original ground have already been occupied. As a result, both government and private agencies are reclaiming different new areas. In most cases, the practice for developing such areas is just to fill lowlands (3~12 m) by dredged material, which is almost silty sand. This is inviting great liquefaction susceptibility for such reclaimed areas. The field SPT N-value of the filling depth varies from 1 to 13. Mean particle diameter and fines content of the fill materials vary from 0.10~0.32 mm and 6~48%, respectively. Liquefaction potential of selected reclaimed areas of the city has been estimated based on standard penetration test and shear wave velocity. It is found that some parts of the reclaimed sites are susceptible to liquefaction up to the filling depth.

This paper presents a seismic hazard assessment of Bandar Abbas in southern of Iran. Four maps have been prepared to indicate the earthquake hazard of this region and its vicinity in the form of iso-acceleration contour lines. They display the probabilistic estimate of Peak Ground Horizontal Acceleration (PGHA) over bedrock for the return periods of 75, 225, 475 and 2475 years, which is the most common criterion in designing and retrofitting of buildings. This region is located at the edge where the Arabian plate pushes forward towards Iran plateau. Southern part of Iran plays an important role in economy of Iran. In this study, seismicity parameters are calculated based on a catalogue of both historical and instrumental earthquakes over an area of 200 km radius around the Bandar Abbas, by Kijko. In order to determine the PGHA, four different attenuation relationships have been used and mixed by using logic tree method. Finally seismic hazard analysis has been performed for region, by SEISRISK III for four hazard levels.

The stability of tailings dams in earthquakes prone areas has become a matter of increasing concern as seismic knowledge has advanced. For the seismic slope stability assessment of tailings dam, majority of current design methodologies rely on the use of pseudo-static approach. However, the crude estimate of finding approximate seismic accelerations makes the pseudo-static approach too conservative to adopt in the stability assessment. In this paper, horizontal slice method is used which considers the seismic inertia forces acting on the sliding wedge of the tailings dam by incorporating the effects of time, phase difference and amplification in shear and primary waves along with the horizontal and vertical seismic accelerations and other soil properties. Results are provided in the graphical form for the stability analysis of tailings dam.