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American Society for Testing and Materials

Statistics and Data Analysis in Geology

Discrete particle simulation of particulate systems: A review of major applications and findings


 The spectral ratio between horizontal and vertical components (H/V ratio) of microtremors measured at the ground surface has been used to estimate fundamental periods and amplification factors of a site, although this technique lacks theoretical background. The aim of this article is to formulate the H/V technique in terms of the characteristics of Rayleigh and Love waves, and to contribute to improve the technique. The improvement includes use of not only peaks but also troughs in the H/V ratio for reliable estimation of the period and use of a newly proposed smoothing function for better estimation of the amplification factor. The formulation leads to a simple formula for the amplification factor expressed with the H/V ratio. With microtremor data measured at 546 junior high schools in 23 wards of Tokyo, the improved technique is applied to mapping site periods and amplification factors in the area.

Ground Motion Characteristics Estimated from Spectral Ratio between Horizontal and Verticcl Components of Mietremors.

A review of the recent advances on the treatment of industrial wastewaters by Sulfate Radical-based Advanced Oxidation Processes (SR-AOPs)

Liquefaction resistance changes with the presence of certain amount of fines in sand but literature related to laboratory and field investigations and the ground behaviour under earthquakes have clearly highlighted the conflicting evidence of the presence of fines on the liquefaction behaviour of sand-fines mixtures particularly low plasticity clay fines. Some studies have indicated decrease in liquefaction resistance with increase in plasticity and vice-versa. The postcyclic undrained shear behaviour of sand and low plasticity are controlled by excess pore pressure ratio and the behaviour is independent of density and confining pressure. In this paper, a series of undrained stress controlled cyclic triaxial shear tests and monotonic undrained shear loading were conducted on reconstituted sample of sand-fines mixtures to evaluate the liquefaction and postliquefaction behavior. Sand was procured from Cauvery river bed, Karnataka, India and locally available low plasticity clay fines were used to prepare sand-fines mixtures. The results indicate that Cyclic Resistance Ratio (CRR) increases with relative density and the post cyclic monotonic strength show increased stress at Ru = 0.

Influence of sand and low plasticity clay mixtures on the liquefaction and postliquefaction behavior

Deterministic seismic hazard analysis (DSHA) has been carried out by considering the historic earthquake, assumed subsurface fault length and point source synthetic ground motion generation model. Active lineaments are identified using remote sensing data. MCE has been determined by considering the regional seismotectonic activity in about 350km radius around Bangalore city. The seismotectonic map has been prepared by considering the faults, lineaments, shear zones in the area and historic earthquake events of more than 150 events. Shortest distance from the Bangalore to the different sources is measured and then Peak Horizontal Acceleration (PHA) calculated for the different sources and moment magnitude using regional attenuation relation. By carrying out sensitivity analysis the matching sub surface rupture length for the each historic earthquake based on Wells and Coppersmith [21]. It is found that subsurface fault rupture length of about 4% of total length of the fault is matching with historic earthquake events in the area close to the each source. SMSIM- FORTRAN programs for simulating ground motions from the Earthquakes have been used by giving the regional seismotectonic parameters as input for the different sources, the PHA for the different locations are evaluated. From the above three approaches the higher PHA causing earthquake moment magnitude of 5.1 is maximum credible earthquake and corresponding source Mandya-ChannapatnaBangalore lineament is obtained as the vulnerable source for Bangalore region. Maximum credible earthquake found in terms of moment magnitude is 5.1 with PHA value of about 0.150g. Acceleration time history (ground motion) of corresponding magnitude has been generated using synthetic earthquake model by considering the revised regional seismotectonic parameter presented in Sitharam and Anbazhagan [18].The revised parameter gives the PHA of 0.146g corresponding to MCE of past event

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Deterministic Seismic Hazard analysis and Estimation of PHA for Bangalore City

This chapter presents the results of the laboratory investigation performed on clay bed reinforced with natural (bamboo) and commercial (geosynthetics) reinforcement materials. 3D cells (similar to geocells) and 2D grids (similar to geogrids) were formed using bamboo known as bamboocells and bamboogrids, respectively. The performance of bamboocells and bamboogrids reinforced clay beds were compared with that of reinforced geocells and geogrids. Bearing capacity of the clay bed is increased by 6 times due to the provision of combination of geocell and geogrid. The ultimate bearing capacity of the bamboocell and bamboogrid reinforced clay bed was found to be 1.3 times that reinforced with geocell and geogrid. Also, substantial reduction in the footing settlement and the surface deformation was observed. The tensile strength and surface roughness of the bamboo were found to be 9 times and 3 times higher than geocell materials. The bamboo was treated chemically to increase the durability. The performance of the bamboo was reduced by 15–20% after the chemical treatment; still the performance was better than its commercial counterparts.

Performance of Bamboo Geocells in Soft Ground Engineering Applications

16). Abstract. In this paper numerical simulation results of isotropic compression and triaxial shear tests on 3-dimensional polydisperse assembly of spheres are reported. The numerical simulations are carried out using discrete element method (DEM). DEM models the granular materials as discrete particles interacting through contact forces. The ntacroscopic behavior of the granular assembly is explained from the micromechanical characteristics of the assemblage such as average coordination number, average contact forces and the orientation of contacts and their distribution.

Micromechanical Modeling Of Granular Materials Using Three Dimensional Discrete Element Modeling

When two footings are placed close enough to each other, they interfere with each other and the soil beneath the footings behaves differently than it would when the footing was isolated. Interference effect causes the soil region between the interfering footings to undergo some sort of confinement due to which the bearing capacity of the soil increases. In this paper, the authors have illustrated how the soil would behave due to interference in clay bed and compared that with clay bed reinforced with geocell confinement. For this, model test experiments were conducted on geocell reinforced clay bed. Three-dimensional numerical simulations using FLAC 3D were run to study parametric study after validating with experimental results. Modified Cam Clay model was used to simulate the behavior of clay bed. Mohr–Coulomb model was used to simulate the behavior of the infill material (i.e., coarse sand). To model the actual shape of the geocell used, the unique and actual curvature of geocell pockets is considered and a realistic approach of modeling is proposed. The optimum spacing (S) between the footings was found to be 0.5 times the width of footing (B) for both unreinforced and geocell reinforced clay beds where bearing capacity is maximum. The maximum interference factor of 1.15 is observed in unreinforced clay. Interference effect is more in geocell reinforced clay than in geogrid-reinforced clay. Maximum interference factor of 1.33 is observed in the case of geocell + geogrid-reinforced clay beds. When the clay was reinforced with geocell and basal geogrid, there was dramatic reduction in the depth of stress distribution, and major stress was accumulated in the geocell membrane preventing the stress distribution to the deeper level.

T. G. Sitharam

Papers

Influence of sand and low plasticity clay mixtures on the liquefaction and postliquefaction behavior

Deterministic Seismic Hazard analysis and Estimation of PHA for Bangalore City

Performance of Bamboo Geocells in Soft Ground Engineering Applications

Micromechanical Modeling Of Granular Materials Using Three Dimensional Discrete Element Modeling

Interference Effect of Footings on Geocell and Geogrid-Reinforced Clay Beds