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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)

Study on Long Wavelength Propagation of Seismic Waves Across Filled Joints Using Resonant Column Experiments

Artificial neural network and support vector machine models for evaluating spatial variability of SPT data

An incident energy wave that propagates across discontinuities in rock mass seldom strikes normal to the joint and an oblique incidence leads to transformation of waves. An obliquely incident vertical shear wave will generate a compression wave as well as a vertical shear wave. Similar transformation happens to P wave also during its transmission. The transformation of an obliquely incident shear wave is numerically simulated with the help of previously validated discrete element model. A parametric study on influence of joint shear stiffness on transformation of shear waves is performed for various angles of incidence. It is observed that joint shear stiffness plays an important role in determining wave velocities and amplitudes of transmitted shear waves across various incident angles, but is insignificant for generated P waves. The dependency of wave velocities and amplitudes of waves on incident wave angles is also discussed in this paper.

Numerical simulation of transformation of an obliquely incident shear wave at rock joint

The rate and magnitude of excess pore water pressure generated during seismic loading considerably influences the shear strength, shear stiffness, deformation and settlement characteristics of soil deposits, thereby affecting the stability of structures constructed from or founded on it. Sometimes the soil may liquefy resulting in a complete loss of strength. A review of related literature on the pore pressure generation characteristics and in turn the cyclic resistance behavior of sandy soils appears to be confusing. In order to clarify and assess the pore pressure generation characteristics of sandy soils, a series of undrained stress controlled cyclic triaxial tests were conducted on various sand and silt mixture specimens of 50mm diameter and 100mm height at various constant gross void ratios. The gross void ratio of a specimen is determined by the ratio of volume of voids to the volume of solids. The results obtained from this study indicate that the limiting silt content and the relative den...

Effect of initial gross void ratio on undrained cyclic pore pressure response of sand-silt mixtures

With rapid urbanization and wide use of underground space, the behaviour of underground structures under various conditions has gained significant attention. Twin tunnels are two closely constructed tunnels. Underground structures are generally supported by the surrounding medium like soil or rock. Due to this additional constraint from the ground, the underground structures are not as vulnerable as compared to the surface structures during an earthquake event. But recent earthquakes have shown that these structures are also prone to damages. Unlike surface structures, the soil-structure interaction is very important in the seismic analysis of underground structures. Moreover, in the case of structures like tunnels, rather than inertial forces the deformation behaviour is controlling the seismic behaviour. The various waves generated during an earthquake event generate additional forces and moments, which may jeopardize the stability of tunnels/underground structures. Among the different types of ground instability associated with seismic loading, the upward and downward movement of the ground due to seismic waves is studied here. In this study, a two dimensional numerical simulation using finite element method is done to understand the response of twin tunnels in weathered type of rock. The dynamic load is applied in the form of earthquake loading. The effect of relative spacing between tunnels is studied when they are subjected to earthquake loading. The results show that due to the dynamic loading the effects on ground settlement is significant especially when the relative spacing between the tunnels is less.

T. G. Sitharam

Papers

Study on Long Wavelength Propagation of Seismic Waves Across Filled Joints Using Resonant Column Experiments

Artificial neural network and support vector machine models for evaluating spatial variability of SPT data

Numerical simulation of transformation of an obliquely incident shear wave at rock joint

Effect of initial gross void ratio on undrained cyclic pore pressure response of sand-silt mixtures

Seismic Response of Twin Tunnels in Weathered Rocks