Mohammad Kazem Jafari

International Institute of Earthquake Engineering and Seismology | iiees · Geotehnical Reaserch Center

The purpose of municipal solid waste landfills (MSWLF) is to dispose non-recyclable materials, gas extraction, composting, and controlling of pollutants that threaten human health and the environment, and finally providing useful areas after filling. Since Iran is located on the seismic belt and has experienced some high intense earthquake, the stu...

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 t...

Seismic loads may damage municipal solid waste (MSW) landfills through the relative movements within the landfill system. These movements can disrupt performance of drainage and gas collection systems, thereby resulting in environmental pollution. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by...

Compared to other types of dams, earthen dams have the largest number in the world and considering the growing trend of earthen dam construction in recent years and the high seismicity in some areas, the analysis and design of large earthen dams against earthquakes and supply Its stability in these loading conditions is of special importance and pr...

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 d...

Traffic, metro and water transmission tunnels in urban areas play a crucial role in supporting the lives of the people, especially after a strong earthquake. They should maintain their stability, serviceability, and strength in such extreme events. Previous studies have shown that the Permanent Ground Deformations (PGD) due to earthquake faulting w...

In the numerical analysis of underground pipelines against dip-slip faulting, it is common practice to model the problem as a beam surrounded by soil-equivalent nonlinear springs. Previous studies have recognised the importance of the Vertical Bearing Soil Springs (VBSS) in the modelling of pipe-fault interaction. Nevertheless, prior studies on VBS...

The permanent ground deformation during the earthquake faulting induces moderate to severe damages to the underground tunnels. The majority of the investigations on the behavior of the tunnels against fault offset were in the rock medium. There is very little available in the literature about the fault-tunnel interaction in alluvial soil. This pape...

روند توسعه گسلش سطحی در یک لایه خاکی تحت تأثیر نوع خاک و خصوصیات آن است. وجود رطوبت در خاک‌های ماسه‌ای، رفتار ژئومکانیکی آن را تغییر می‌دهد. در آزمایش‌های مدل‌سازی فیزیکی به دلیل قابل‌توجه بودن چسبندگی ظاهری ایجادشده در خاک که به دلیل وجود آب میان دانه‌ای است با سطح تنش همه‌جانبه مدل کوچک‌مقیاس، رطوبت به‌شدت بر رفتار گسلش تأثیرگذار است. در مدل‌سازی...

This study mainly aims to assess the performance of soil-structure systems designed by direct displacement-based method coupled with strong column-weak beam design concept through various system identification techniques under strong ground motions. To this end, various system identification methods are employed to evaluate the dynamic characterist...

Based on inversion of the horizontal-to-vertical spectral ratio of microtremors (H/V), the empirical H/V spectrum of surface waves propagating on a layered half-space was studied and the effects of soil layers on fundamental and higher peak frequencies were considered. Using the Nakamura H/V spectral method and comparing it with the analytical site...

وجود آب میان‌دانه‌ای باعث ایجاد چسبندگی ظاهری در خاک‌های دانه‌ای و تغییر رفتار برشی آن‌ها می‌شود. همین چسبندگی ظاهری اندک، اثرات بزرگی بر پدیده‌های ژئوتکنیکی، همچون گسلش سطحی، دارد. در این تحقیق، اثر آب میان‌دانه‌ای بر تغییر رفتار برشی خاک‌های دانه‌ای مورد مطالعه قرار گرفت. از آزمایش‌های برش مستقیم و مدل‌سازی فیزیکی گسلش برای بررسی استفاده گردید. ر...

وجود رطوبت بین‌دانه‌ای باعث تغییر رفتار ژئومکانیکی خاک‌های دانه‌ای می‌گردد. تاکنون، اغلب مدل‌سازی عددی گسلش سطحی بر روی ماسه‌های خشک انجام شده است. روند توسعه گسلش سطحی بر روی خاک‌های دانه‌ای مرطوب چندان مورد یررسی قرار نگرفته است. در تحقیق حاضر اثر رطوبت با تغییر پارامترهای ژئومکانیکی خاک با استفاده از نرم‌افزار المان محدود پلکسیس 2017 در نظر گرفت...

Surface fault rupture has been previously investigated in dry cohesionless soil; however, wet granular soil has not been investigated in detail; however, apparent cohesion induced by intergranular water causes granular soil to behave differently than dry cohesionless soil. Field evidence shows that all soil that has been wetted will experience some...

Despite of the limitation in modeling infinite space, the finite element method (FEM) is one of the most used tools to numerically study the geotechnical problems regarding the capacity of simulating different geometries, conditions and material behaviors. A kind of absorbing layer named perfectly matched layer (PML) has been applied to modeling th...

Shear modulus (G) and damping ratio (D) are efficient and important parameters in estimation of seismic response of a site. Recently by development of the advanced experimental equipment, some studies have been presented based on the dynamic parameters of unsaturated soils. It is tried to find the variation of the cyclic parameters of the unsaturat...

Surface wave identification is one of the conventional parts of site effect studies. Geophysical approaches reveal information about the medium that the waves propagate through. In case of site effect studies, researchers are interested in Rayleigh and Love waves. Ambient vibrations, called microtremors, imitate the surface wave’s behaviors which v...

Study of the seismic response of a site, requires accurate estimation of the Shear modulus (G) and damping ratio (D) of underground 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 oth...

Single station ambient noise measurements were performed in 122 points on a complex landslide at the left bank of Latian Dam reservoir in the north-east of Tehran (Iran), to investigate the seismic site response of a landslide, especially the nature and causative factor of directional site amplification. Recorded data were analyzed through the hori...

Seismic loads may damage municipal solid waste (MSW) landfills through the relative movements within the landfill system. These movements can disrupt performance of drainage and gas collection systems, thereby resulting in environmental pollution. The smooth synthetic materials might be placed beneath the structures to provide seismic protection by...

In many applied engineering problems, structural analysis is usually conducted by assuming a rigid bed, while imposing the effect of structure bed flexibility can affect significantly on the structure response. This article focuses on investigation and evaluation of the effects arising from considering a soil-structure system in evaluation of dynam...

Some fault rupture propagation tests were conducted in which wet soil were used to model a cohesion soil in real condition. Results of these tests show that by increase of water content, the shear band of fault rupture propagate in a narrower zone so the distorted area above the ground was decreased. Ductile soil has the ability to deform more befo...

کاهش چسبندگی خاک‌های چسبنده برای مدل‌سازی فیزیکی در محیط 1g با افزایش آب به آن، در موارد بسیاری عملی نیست. در برخی موارد می‌توان از خاک دانه‌ای مرطوب به عنوان جایگزینی برای مدل‌سازی خاک‌های چسبنده استفاده نمود. در این راستا، اثر رطوبت بر پارامترهای مقاومتی خاک‌های دانه‌ای با استفاده از آزمایش‌های برش مستقیم بررسی شدند. این آزمایش‌ها بر روی خاک ماسه...

A series of 3D dynamic numerical analyses were conducted to explore the mechanical behaviour of a mixture of coarse gravel-size particles floating in a matrix of clay (composite clay), under cyclic loading. Composite clay is used as the core material of some large embankment dams, some of which are located in areas of high seismicity. A predominant...

Reducing the static and seismic earth pressures on geotechnical structures, such as retaining walls, bridges abutments and buried pipes, using compressible materials is a novel idea which has received increased consideration during recent years. Despite the high compressibility of injectable polyurethane (PU) foams, their performance as a compressi...

According to the considerable effects of the loading frequency on the cyclic behaviour of the soils and lack of the sufficient and precise data in this field for the unsaturated soils, more attention needs to be paid to the experimental investigations in various loading paths and frequencies. Meanwhile the unsaturated cyclic tests require advanced...

In order to assess and compare efficiency of triangular and orthogonal arrays in identification of subsurface structure specifications up to a depth of 50 meters using microtremor waves by F-K method, two triangular and orthogonal arrays with 13 and 12 stations (which included some sub-arrays), respectively, were studied in a site located in north...

Experimental study of the cyclic behavior of unsaturated materials is more complex than that of the saturated materials due to the required equipment, experience and time. Furthering investigations in the field of unsaturated materials is necessary to better understand its complexity and sensitivity of unsaturated cyclic parameters to different det...

Due to the damages of many structures like buildings, bridges, dams, tunnels and etc., by the permanent relative displacement of surface fault, it is too important to investigate fault rupture propagation. The occurrence of three tremendous earthquakes of 1999 in Turkey and Taiwan was the start of a comprehensive study of the fault rupture propagat...

This paper presents the results of a numerical parametric study on the seismic behavior of 2D triangular-shaped valleys subjected to vertically propagating incident SV waves. The medium is assumed to have a linear elastic constitutive behavior. All calculations are executed in time-domain utilizing the spectral finite element method. Clear perspect...

This paper examines the interaction between urban tunnel and ground surface during the different input motions. The Niyayesh–Sadr tunnel in North of Tehran with a 14m span and its environmental conditions were used as a case study. Analysis is performed using a finite difference model which takes into consideration the presence of the tunnel during...

In this paper, an advanced formulation of the spectral finite element method (SFEM) is presented and applied in order to carry out site response analysis of 2D topographic structures subjected to vertically propagating incident in-plane waves in time-domain. The accuracy, efficiency and applicability of the formulation are demonstrated by solving s...

The anisotropy of sand–silt mixtures has not been fully studied in terms of the effects of different grain shapes and silt content. This study investigated the effects on anisotropy in three different sands with various silt contents and grain shapes. The tests performed in this research include 90 hollow cylinder torsion shear tests conducted on t...

Monotonic triaxial compression, triaxial extension and torsional shear tests were carried out on geotextile reinforced sand and reinforced clay, mainly to investigate the effects of rotation of principal stresses on the mechanical behavior of the reinforced soil materials. The tests were carried out on unreinforced and reinforced specimens with 2,...

This paper presents time domain fundamental solutions for the extended Biot's dynamic formulations of two-dimensional (2D) unsaturated poroelasticity. Unsaturated porous media is considered as a porous media in which the voids are saturated with two immiscible fluids, i.e. liquid and gas. At first, the corresponding explicit Laplace transform domai...

This paper extends a method, which has been previously called half-plane time-domain boundary element method (BEM) and successfully applied to 2-D concave topographies, for analysing convex irregular sites subjected to vertically as well as obliquely propagating incident SH waves. While using this method, only interface and surface of the hill need...

In this paper, different amplification patterns of 2-D semi-sine shaped valleys and their beyond were presented due to vertically propagating incident out-of-plane SH waves. The half-plane time-domain BEM approach which was proposed by the authors was used to obtain the results. Compared to the previous studies on boundary elements, avoiding from a...

In this paper, an advanced formulation of Time-domain, two-dimensional Boundary Element Method (BEM) with material damping is presented. Full space two-dimensional visco-elastodynamic time-convoluted kernels are proposed in order to incorporate proportional damping. This approach is applied to carry out site response analysis of viscoelastic topogr...

Microtremor data have been carried out for microzonation studies and disaster mitigation in urban areas. Over a period of two decades, the Nakamura's H/V spectral ratio method was recognized as a simple and cost effective method in seismological geotechnics. In order to identify the soil layers characteristics, microtremor measurements were perform...

During past earthquakes, many instances of building damage as a result of earthquake surface fault rupture have been observed. The results of investigating a potential mitigation scheme are presented in this paper. Such plan provides a wall in the soil with the aim of surface displacement localization in the narrow pre-determined location. This may...

When seismic thrust faults emerge on the ground surface, they are particularly damaging to buildings, bridges and lifelines that lie on the rupture path. To protect a structure founded on a rigid raft, a thick diaphragm-type soil bentonite wall (SBW) is installed in front of and near the foundation, at sufficient depth to intercept the propagating...

In this paper, a half-plane time-domain boundary element method (BEM) was presented for analysing the 2-D scalar wave problems in a homogenous isotropic linear elastic medium. Using the existing transient full-plane fundamental solution and asking for the assistance of method of source image to satisfy the stress-free boundary conditions, first, a...

The characteristics of near-fault and far-field earthquakes differ. Records suggest that a near-fault ground motion is characterized by a large high-energy pulse and a distinctive pulse shape for the velocity time history. The present study compared near-fault and far-field ground motion effects and investigates the consequence of well-known charac...

In this paper, an advanced formulation of a time-domain two-dimensional boundary element method (BEM) is presented and applied to calculate the response of a buried, unlined, and infinitely long cylindrical cavity with a circular cross-section subjected to SV and P waves. The applicability and efficiency of the algorithm are verified with frequency...

Spatial Variation of Earthquake Ground Motion (SVEGM) is clearly indicated in data recorded at dense seismographic arrays. The main purpose of this paper is to study the influence of SVEGM on the seismic response of large embankment dams. To this end, the Masjed Soleyman embankment dam, constructed in Iran is selected as a numerical example. The sp...

Near-fault seismic records strongly influenced by forward directivity are characterized by one or more large pulses in velocity time histories. The characteristics of these records are significantly different from ordinary records. This study evaluated the correlation between the intensity indices of pulse-like ground motion and crest settlement of...

In this paper, an advanced formulation of a time-domain two-dimensional boundary element method (BEM) is presented and applied to calculate the response of a buried, unlined, and infinitely long cylindrical cavity with a circular cross-section subjected to SV and P waves. The applicability and efficiency of the algorithm are verified with frequency...

In this paper, normalized displacement amplitude of the ground surface was presented in the presence of the semi-sine shaped valley above the truncated circular cavity embedded in a homogenous isotopic linear elastic half-plane, subjected to obliquely propagating incident SH waves as Ricker wavelet type. The proposed direct time-domain half-plane b...

In this document, a boundary element formulation was presented to analyze the valley shaped topography features in the time domain. Despite the studies performed by time-domain boundary element method (BEM) for the seismic analysis of topography features, the smooth ground surface was not required to be discretized and the valley surface only neede...

This paper focuses on examining the combined effects of frequency content and spatial variability of the ground motion on the response of a large embankment dam. A series of nonuniform ground motion time histories are generated using spectral representation method. The influence of frequency content of seismic excitation is taken into account by us...

Collapsible soils have considerable strength and stiffness in their dry natural state but settle dramatically when they become wet. This paper documents a low-cost, qualitative evaluation scheme using fuzzy set analysis to determine site collapsibility based on subjective knowledge of the geological, geotechnical, and environmental conditions and t...

In order to develop underground structures such as subways, metro tunnels and other buried facilities in big cities, the dynamic interaction of these structures and their environment should be considered. Previous studies based on series solution in frequency domain showed that, in existence of a tunnel, the free-field motion of surrounding soil is...

As a step forward in an ongoing investigation on behavior of composite clay, which is used as the core material of some large embankment dams all over the world, a series of experiments were conducted to explore the distribution of excess pore water pressure along saturated triaxial clay specimens during cyclic loading. As the predominant feature o...

A series of tests and also numerical analyses were conducted to explore the mechanical behavior of a mixture of coarse gravelsize particles floating in a matrix of silt, sand or clay. The research is a step forward in an ongoing investigation on behavior of composite clay, which is used as the core material of some large embankment dams all over th...

An experimental study has been carried out to investigate the effects of isotropic compression, wetting, and drying on the initial shear stiffness of Zenoz kaolin, an unsaturated lean clay, both in normally consolidated and overconsolidated conditions. The proposed study was conducted using fixed–free resonant column – torsional shear (RCTS). Speci...

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,...

Technically speaking, there are different methods for seismic analysis of topographic features which include analytical, semi-analytical and numerical ones. 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...

Unsaturated soils are considered as porous continua, composed of porous skeleton with its pores filled by water and air. The governing partial differential equations (PDE) are derived based on the mechanics for isothermal and infinitesimal evolution of unsaturated porous media in terms of skeleton displacement vector, liquid, and gas scalar pressur...

Shear modulus and damping ratio are important input parameters in dynamic analysis. A series of resonant column tests was carried out on pure clays and sand-clay mixtures prepared at different densities to investigate the effects of aggregate content, confining stress, void ratio and clay plasticity on the maximum shear modulus and minimum damping...

Using a sequential procedure of undrained cyclic and post cyclic tests, the strength and stiffness degradation characteristics of compacted composite clays are studied immediately after various cyclic loading paths by triaxial and hollow cylinder tests. The effects of cyclic loading paths, sand contents, cyclic loading amplitude and confining press...

An important step in effectively reducing seismic risk and the vulnerability of a city located in an earthquake prone area is to conduct a ground motion microzonation study for the desired return period. The International Institute of Earthquake Engineering and Seismology (IIEES) initiated a number of seismic microzonation projects for Iran. This p...

The cyclic triaxial test is the most widely used way to measure the cyclic stress-strain properties of saturated soils because of its availability in most geotechnical laboratories. Further, it can be viewed as a suitable tool with which to analyze the cyclic behavior of unsaturated soils in a wide strain range. In this study, a new stress path suc...