In order to evaluate the effects of soil box boundary conditions on the dynamic soil behavior, the Rigid Box (RB) and the Laminar Shear box (LSB) were constructed and 1 g shaking table tests were carried out for various boundary conditions. The boundary effects of the RB and the LSB were compared. To reduce the boundary effects of the RB, sponges, 5 cm, 10 cm, and 15 cm in thickness, were attached to the two end sides of the RB. A model soil was constructed on flat ground, and the acceleration and amplification occurring in the center of the soil were analyzed by spectrum and peak ground acceleration. Compared with the RB, the center and wall accelerations of LSB were very close to each other. This implies that the LSB can better simulate the behavior of the infinite half space than the RB.

CO₂ hydrates are ice-like solid lattice compounds composed of hydrogen-bonded cages of water molecules that encapsulate guest CO₂ molecules. The formation of CO₂ hydrates in unconsolidated sediments significantly decreases their permeability and increases their stiffness. CO₂ hydrate-bearing sediments can, therefore, act as cap-rocks and prevent CO₂ leakage from a CO₂-stored layer. In this study, we conducted an experimental simulation of CO₂ geological storage into marine unconsolidated sediments. CO₂ hydrates formed during the CO₂ liquid injection process and prevented any upward flow of CO₂. Temperature, pressure, P-wave velocity, and electrical resistance were measured during the experiment, and their measurement results verified the occurrence of the self-trapping effect induced by CO₂ hydrate formation. Several analyses using the experimental results revealed that CO₂ hydrate bearing-sediments have a considerable sealing capacity. Minimum breakthrough pressure and maximum absolute permeability are estimated to be 0.71 MPa and 5.55 × 10⁻⁴ darcys, respectively.

In order to verify the reliability of numerical analysis, a series of 1 g shaking table tests for flat ground and slope were conducted using a laminar shear box subjected to different seismic waves. Firstly, numerical analyses, using the DEEPSOIL and ABAQUS software, were done to compare the results of flat ground experiments. After that, finite element analyses with ABAQUS were conducted to compare the results of slope experiments. For numerical analyses, considering the influence of the boundary, the concept of adjusted elastic modulus was proposed to improve the simulation results. Based on the analyses, it is found that in terms of acceleration-time history and spectral acceleration, the numerical analysis results are in good agreement with the experiment results. This implies that numerical analysis can capture the dynamic behavior of soil under 1 g shaking table test conditions.

The seismic performance of slopes is typically evaluated with a pseudo-static method using equivalent horizontal load or with Newmark sliding block analysis. In both procedures, the definition of the potential sliding surface is a required input. The sliding surface has been reported to be marginally influenced by the input ground motion and, therefore, is most often assumed from a pseudo-static procedure. In this study, extensive series of two-dimensional dynamic nonlinear finite element analyses are performed to evaluate the sensitivity of the sliding surface on the slope geometry, soil strength parameters, and input ground motion characteristics. It is demonstrated that the sliding surface may vary with the intensity and frequency characteristics of the input motion. Slopes with inclination angle equal or less than 35° are shown to be marginally influenced by motion intensity if the mean period (T_m) < 0.3 s. However, slopes inclined at 45° are revealed to be more sensitive to the motion intensity and T_m. For motions with T_m > 0.3 s, the sliding surface is demonstrated to widen with an increase in the intensity of the input ground motions. The degree of widening increases proportionally with an increase in T_m. It is, therefore, recommended to derive sliding surfaces from a dynamic analysis for steep slopes.

Characterization of ground motion incoherency can significantly reduce the seismic load imposed on large scale infrastructures. Because of difficulties in developing an empirical coherency function from a site-specific dense array, it is seldom used in practice. A number of studies used numerical simulations to develop generic coherency models. However, they have only been developed for idealized profiles. A comprehensive parametric study evaluating the effect of various parameters influencing the calculated coherency function has not yet been performed. We utilized the measured shear wave velocity (V_s) profile at Pinyon Flat, located in California, to perform a suite of time history analyses. This site was selected because the empirical coherency function developed here has been used as a reference model for rock sites. We performed several sensitivity studies investigating the effect of both the site spatial variability and numerical analysis parameters in order to provide a guideline for developing a coherency model from numerical simulations. The outputs were compared against the empirical coherency model to better illustrate the importance of the parameters. The coefficient of variation (CV) of V_s was revealed to be the primary parameter influencing the calculated plane-wave coherency, whereas the correlation length (CL) has a secondary influence. Site-specific convergence analyses should be performed to determine the optimum numerical parameter, including the number of analyses and depth of numerical model. Considering the importance of CV and V_s, it is recommended to perform field tests to determine site-specific values to derive numerical coherency functions.

The assessment of spatial variability in the ground through field experiments has many constraints due to non-homogenous ground conditions and lack of site investigations. For this reason, spatial variability has not been considered in typical analyses. Also, few studies have been conducted on ground spatial variability using models in the laboratory. However, it is necessary to evaluate spatial variability in the ground for more precise analysis and design of construction projects. In this study, in order to evaluate spatial variability in the ground, we performed a number of Mini-Cone Penetration Tests (CPTs) in ground models with one layer of silica sand soil and two layers of silica and weathered soils. Through the Mini-CPTs, cone penetration resistances with depth were measured at many points. Based on the data, the coefficient of variation (CV) and the correlation length (CL) were calculated to quantitatively analyze the vertical and horizontal variability in the ground models. The results showed how the spatial variability in the two ground models varied. This implies that considering spatial variability in the ground can significantly enhance the accuracy of the analysis and design of construction projects.