Hydro-mechanical coupling in numerical analysis of geotechnical structures under multi-directional seismic loading

摘要

This thesis numerically investigates the seismic behaviour of geotechnical structures under multi-directional loading by employing the coupled hydro-mechanical (HM) formulation of the Imperial College Finite Element Program (ICFEP). The scope of the research work can be summarised as follows:ududFirstly, the stability of the generalised-α method (CH method) for the coupled consolidation formulation, is analytically investigated for the first time and the corresponding theoretical stability conditions are derived. The analytically derived stability conditions are validated by finite element (FE) analyses considering a range of loading conditions and soil permeability values.ududSecondly, the site response due to the vertical component of the ground motion is systematically investigated by employing analytical and numerical methods. The compressional wave propagation mechanism in saturated porous soils is investigated by the coupled HM formulation. Furthermore, the undertaken coupled FE analyses explore the effects of the parameters characterising the hydraulic phase, i.e. the soil permeability and soil state conditions, on the vertical site response.ududThirdly, three-directional (3-D) site response analyses are conducted for the HINO site of the Japanese KiK-net down-hole array earthquake monitoring system. Different aspects of the numerical modelling for the site response analysis, such as the constitutive model, the use of 3-D input motion and the coupled consolidation formulation, are investigated and validated by the recordings from the KiK-net system. Further parametric studies investigate the impact of the variation of the water table, the soil permeability and the 3-D input motion on the multi-directional site response.ududFinally, the seismic response of a well-documented Chinese rockfill dam, the Yele dam, is investigated with the dynamic plane-strain FE analysis, accounting for the HM coupling and nonlinear soil response. The numerical predictions are compared against the available static and dynamic monitoring data, which allows for a rigorous validation of the developed numerical model. Furthermore, parametric studies of the Yele dam are conducted to explore the effects of several critical factors on the seismic response of rockfill dams, i.e. the reservoir simulation method, the permeability of materials comprising the dam body, the vertical ground motion and the reservoir water level.