Xie, Mian; (2025) Analysis of slope stability using a robust soil-water interaction Material Point Method. Doctoral thesis (Ph.D), UCL (University College London).

Text Mian_Xie_PhD_Thesis_Final.pdf - Accepted Version Access restricted to UCL open access staff until 1 November 2027. Download (58MB)

Abstract

This thesis develops a comprehensive computational framework, aiming to model the complete process of landslide from initiation, through propagation, to the generation of waves when landslides interact with free-surface water. This research addresses critical gaps in existing numerical approaches that typically struggle with either the triggering or propagation of landslides, making them unsuitable for simulating the entire landslide process within a unified framework. The methodology incorporates five interconnected innovations: (1) implementation of advanced constitutive models within a large strain framework, with particular emphasis on the SANISAND model with fabric-enhanced dilatancy; (2) development of robust numerical stabilisation techniques for the Material Point Method (MPM), including B-spline shape functions that completely eliminate cell-crossing noise, and a modified F-bar method that efficiently mitigates volumetric locking instability; (3) creation of an efficient semi-implicit two-phase double-point MPM formulation that enables separate but coupled modelling of soil and water phases; (4) provision of additional stabilisations for intense soil-water interaction problems with high Reynolds number flows; and (5) validation against well-documented case studies of seismic-triggered liquefaction landslide. A key advancement is the stabilised semi-implicit double-point formulation, enabling time steps about 250 times larger than conventional explicit methods, which makes it feasible to simulate realistic large-scale problems within practical timeframes. The proposed framework is systematically validated throughout the thesis against analytical solutions, and numerical and experimental studies across multiple scenarios, from one-dimensional consolidation to complex soil-water interactions, including dam breaks and granular flow-induced tsunamis. The culmination of this work is demonstrated through the comprehensive simulation of the 1971 Lower San Fernando Dam failure, where the model successfully reproduces the entire failure process from seismic-triggered liquefaction through propagation to final stabilisation. Using model parameters calibrated against laboratory tests, reported in the literature, on samples collected on-site, the simulation achieves closer agreement with observed post-failure geometry than previous studies, while maintaining numerical stability throughout without requiring artificial damping.

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