Department of Soil and Foundation (2004 - Present)
Civil Engineering
, Tokyo, Japan
Rock Mechanics
Civil Engineering, Tokyo, Tokyo, Japan
Civil Engineering-Rock Mechanics
Civil Engineering, The University of Tokyo, Tokyo, Japan
Civil Engineering
, University of Tehran, Iran
Soil Mechanics and Foundation Engineering
Civil Engineering, The University of Tehran, Tehran, IRAN
Civil Engineering
Civil Engineering, The University of Tehran, Tehran, IRAN
Civil Engineering
, University of Tehran, Iran
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Dr. Mahmoud Yazdani is an expert in fundamental and applied geotechnical engineering and rock mechanics. He has a proven track record of experience and a distinct combination of skill set including engineering design, research innovation, computer-aided calculation, numerical analysis, programming, project management, industry engagement, and experimental tools development. He has over 27 years of professional, academic and research experience in the areas of geotechnical and structural engineering and conducted consulting to industry, theoretical and applied research, teaching, project implementation and technical supervision. He has successfully accomplished several granted projects and numerous publications including books, papers, and guidelines. His fields of expertise cover a range of topics, including: geotechnics and rock mechanics, structural engineering, subsurface exploration, underground excavation, fluid flow and hydro-mechanical coupling, monitoring and back analysis. Since 2003, he has served as the academic member of civil engineering department in graduate university of Tarbiat Modares in Tehran. During this period, he worked as the head of geotechnical engineering group (2 years), the educational deputy (4 years) and also the general director of technical office and civil engineering projects of the university (3.5 years). With his multidisciplinary background, he has much been active collaborator and accomplished 3 research joint projects with professionals from worldwide highly ranked universities. He has supervised 3 PhD and 50 master research thesis and currently is the principal supervisor for 4 PhD and 6 master students. He has been the author and co-author of 4 books and over 130 refereed publications in different journals, various conference and symposia proceedings and has produced more than 150 geotechnical engineering reports. He has accomplished 15 research projects funded by private clients, Ministry of Water and Energy, Ministry of Roads and Urban Development, Housing Foundation in Iran and also Korea Institute of Geoscience and Mineral Resources (KIGAM). Through the supervision of over 10 master thesis, he has extended the application of Taguchi method (known generally for design of experiments) to obtain many benefits in a wide range of civil engineering and geotechnical practices. Using this approach, he used limited systematic analyses based on orthogonal arrays to achieve model calibration and parameter determination by back analysis of experiments, mix design of lightweight concrete, optimization of design support for deep excavation, etc. Mahmoud has many years of hands-on experience in dam and hydro-power plant projects involved in design, construction, and quality control teams collaborating with technical committees of high ranked national and international firms. He was involved in several large dam and hydro-power plant projects including: Saveh dam, Bakhtiyari dam, Seymareh dam, Karkheh dam, Gotvand dam, Karun IV dam in Iran and Roqun dam in Tajikistan. Besides the academic endeavor, he has established a private consulting engineering research company since 2007 and applied new technical approaches in deep excavation practices and developed innovative tools for in-situ shear strength and plate loading tests which successfully applied in parameter determination of numerous geotechnical projects including very deep excavations. Based on his knowledge on rock mechanics, he used porous lightweight aggregates of LECA and Pumice in cement concrete and for the first time in the country designed and constructed some reinforced concrete buildings in Tehran using structural lightweight concrete.
In the current experimental work, the simultaneous effect of fineness modulus, water-to-cementitious materials [W/(C+M)], and also micro silica content were investigated on workability, mechanical and physical properties of high strength concrete. For this purpose, 45 mix-designs were made by selecting five different ratios of micro-silica, three W/(C+M) ratios, and three distributions of particle size and then the slump, compressive strength, elastic modulus, and split tensile strength of each designed concrete mixture were determined. Findings showed that increasing the micro-silica content up to 10 wt% improves the mechanical properties of concrete and then leads to a reduction in strength parameters, so that the effect of changes in the
Loose specimens with a void ratio of 0.86, corresponding to a relative density of 30% for the pure sand, and normal stresses of 50, 100 and 150 kPa were used in this work to study strength and deformation behaviour of sand rubber mixtures. Three types of rubber particles with D-rubber/D-sand?=?0.25, 1, and 4, and different rubber to sand ratio of 5, 10, 15, 20, 25, 30, 40 and 50% were investigated by performing more than 300 direct shear tests. The shear strength and deformation characteristics of sand-rubber mixtures were dependent on rubber proportions of the mixtures and size ratio. Angle of friction and cohesion intercept increased and reduced when up to 20% rubber fraction was used, but reduced and increased afterwards. Di
This paper presents a comparison between experimental measurements and numerical estimations of penetration length of a cement grout injected in discrete joints. In the experiment, a joint was generated by planar acryl plates with a certain separation distance (; aperture) and was designed in such a way to vary the separation distances. Since a cement grout was used, the grout viscosity can be varied by controlling water-cement (W/C) ratios. Throughout these experiments, the influence of joint aperture, cement grout viscosity, and injection rate on a penetration length in a discrete joint was investigated. During the experiments, we also measured the time-dependent variation of grout viscosity due to a hardening process. The time-dependent
Investigations of the growth, interaction, and coalescence of cracks are important because they help to provide tools for the more realistic modeling of rock masses containing low persistence discontinuities and better estimations of the strength and stiffness of a rock material. Understanding the coalescence mechanism is useful for justifying the mechanism of continental crustal deformation, evaluating the structural failure of slopes with rock bridges, and analyzing the stability of tunnels when a mode I or mix mode failure mechanism is involved. The evaluation of crack growth can provide valuable information about the mechanism for the formation of new geological structures, and the formation, evolution, and growth of faults. This paper
There are numerous old arch bridges in Iran that have been used as railway bridges for more than 70 years. Field load testing of old railway bridges in km-23 and km-24 of Tehran–Qom railway have revealed important characteristics of the bridges and have proven that there is still a large capacity under service load. Since most of these bridges are not designed for earthquake excitation, seismic vulnerability of these structures is uncertain. This fact necessitates the investigation of the earthquake resistance of these kinds of bridges. In this paper, seismic performance of bridges is assessed by the pushover analysis. These bridges are plain concrete arch structures with different span length and mechanical properties which have been bui
The precision and speed of numerical simulations of physical phenomena has led to their increasing use in designing and research applications. These precision and speed are owed to the improvements in numerical methods and significant advancements in computing power of CPUs and GPUs.Particle-based methods are some of the most recently developed numerical simulation methods. Development of these methods has been long delayed due to the need for a relatively high computational effort.
Understanding initiation and growth of cracks leads to better evaluation of rock masses behavior. Investigation of crack growth and propagation is noteworthy in geotechnical engineering, petroleum engineering, geology, seismology and many other sciences which encounter with rock fracture mechanics problems. Evaluation of rock slopes stability, design of retaining structures, design of tunnels, and prediction of flow path through rock masses, are some example of application of crack growth study in geotechnical engineering. By evaluating cracks growth, propagation and coalescence, faults seismic behavior can be understood. In general faults are considered as quasi-static cracks, so study of crack propagation under various loading conditions
A numerical analysis of coupled viscous fluid flow and joint mechanical deformation was developed to estimate penetration length of cement grout. The coupled analysis was established using discrete element method (DEM) such that parameters of both individual joint and discrete network can be implemented without difficulty in estimating grout penetration in a jointed rock mass. For a verification of the established numerical analysis, the results of penetration length in 1-dimensional linear flow analysis was compared to previous analytical solution. We also showed that the estimated penetration radius in 2-dimensional radial flow analysis was well comparable to our experimental observation of cement grout injection in a rock joint replica.
Fluid flow modeling is a major area of interest within the field of rock mechanics. The main objective of this study is to gain insight into the performance of grout injection inside jointed rock masses by numerical modeling of grout flow through a single rock joint. Grout flow has been widely simulated using non-Newtonian Bingham fluid characterized by two main parameters of dynamic viscosity and shear yield strength both of which are time dependent. The increasing value of these properties with injection time will apparently affect the parameters representing the grouting performance including grout penetration length and volumetric injection rate. In addition, through hydromechanical coupling a mutual influence between the
This paper presents a new procedure for determining the fracture toughness of rock-like specimens using the diametric compression test with the center-cracked horseshoe disk (CCHD) method. Using finite element analysis, a dimensionless stress intensity factor was obtained and a formula was rendered for determining mode I fracture toughness. To evaluate the accuracy of the measurement results produced by the CCHD method, fracture toughness experiments were conducted on the same rock-like material using the notched Brazilian disk (NBD) method. The CCHD tests were simulated using a two-dimensional particle flow code for validation of the experimental results, and a great agreement between the pattern of crack initiation and prop
Artificial lightweight aggregates have a wide range of applications in industry and engineering. Nowadays, the usage of this material in geotechnical activities, especially as backfill in retaining walls has been growing due to the specific characteristics which make it a competent alternative to the conventional geotechnical materials. In practice, a material with lower weight but higher shear strength parameters would be ideal as backfill behind retaining walls because of the important roles that these parameters play in decreasing the overall active lateral earth pressure. In this study, two types of Light Expanded Clay Aggregates (LECA) produced in the Leca factory are investigated. LECA is made in a rotary kiln by heating natural clay
Determination of soil engineering properties such as shear strength is essential to analysis many geotechnical problems. Therefore, determination of the reliable values for this parameter is very important. For this purpose, direct shear test as one of the oldest test to examine the shear strength of soils, is conducted on soil samples. There are too many factors which could affect results of direct shear test. Laboratory tests are expensive, difficult and time consuming, hence using numerical method to simulate experimental test and study effective factors can be useful. In this paper direct shear test was numerically modeled using CA2 hybrid finite element-discrete element method code. CA2 solves explicitly equations of motion together wi
Nowadays, soil nailing is widely used to stabilize slopes and excavations. The bond strength is integrated shear strength along the interface area between grout and soil. Choosing a value for bond resistance is one of the effective parameters in nailed wall design, which is generally determined by the values proposed by FHWA guidelines. A designer uses a high safety factor that makes the design safe but sometimes it is not economical. Therefore, in this study, an attempt is made to investigate the effects of overburden, injection pressure and soil strength parameters on the bond strength of nails in field. For this research, five different sites in Tehran were considered with a total number of 20 soil–nail pull-out test. Values such as co
In this paper, a numerical analysis of one-dimensional viscous fluid flow in a rock joint using UDEC code is performed to evaluate the effect of design parameters on injection performance. We consider injection pressure, fluid compressibility, time dependence of yield strength and viscosity of injected grout fluid, and mechanical deformation of joint as the design parameters, and penetration length and flow rate of injection are investigated as the injection performance. Numerical estimations of penetration length and flow rate were compared to analytical solution and were well comparable with each other. We showed that cumulative injection volume can be over-estimated by 1.2 times than the case that the time-dependent viscosity evolution i
A fully coupled non-linear effective stress response finite difference (FD) model is built to survey the counter-intuitive recent findings on the reliance of pore water pressure ratio on foundation contact pressure. Two alternative design scenarios for a benchmark problem are explored and contrasted in the light of construction emission rates using the EFFC-DFI methodology. A strain-hardening effective stress plasticity model is adopted to simulate the dynamic loading. A combination of input motions, contact pressure, initial vertical total pressure and distance to foundation centreline are employed, as model variables, to further investigate the control of permanent and variable actions on the residual pore pressure ratio. The model is ver
Determination of rock engineering properties is important in civil, mining and geotechnical engineering. Uniaxial Compressive Strength (UCS) is one of the most important properties of rocks. Point Load Test (PLT) is practically used in geotechnical engineering to determine rock strength index. Despite that the PLT is fast, economical and simple in either field or laboratory, Uniaxial Compressive Test (UCT) is time-consuming and expensive. UCS can be estimated using Point Load Index (PLI). So, implementation of correlation between results of PLT and UCT is of interest. In this research correlation between the results of point load test and uniaxial compressive test are presented for rock samples from three sites in Iran. Two rock types inclu
Purpose – The purpose of this paper is to find a convenient contact detection algorithm in order to apply in distinct element simulation. Design/methodology/approach – Taking the most computation effort, the performance of the contact detection algorithm highly affects the running time. The algorithms investigated in this study consist of Incremental Sort-and-Update (ISU) and Double-Ended Spatial Sorting (DESS). These algorithms are based on bounding boxes, which makes the algorithm independent of blocks shapes. ISU and DESS algorithms contain sorting and updating phases. To compare the algorithms, they were implemented in identical examples of roc
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