arXiv subjects

Mian Xie

Publications and source records attributed to Mian Xie.

4 recordsLinked to original sources

arXiv2026

A semi-implicit double-point Material Point Method for both free-surface flow and seepage in deformable porous media

A new semi-implicit, two-phase, double-point formulation of the Material Point Method (MPM) for soil-water interaction with seepage and free-surface flows under large deformation is presented in this paper. The approach advances the water phase implicitly while keeping the soil phase explicit, enabling stable, efficient time integration in problems that involve rapid seepage and strong free-surface motion. The proposed framework models high-Reynolds-number interphase drag through a non-linear Darcy's law implemented for the first time within an incremental fractional step MPM formulation without enlarging the implicit solve. This methodology also enhances the numerical stability for fast flows and wave breaking via a hyperelastic constitutive treatment of slightly compressible viscous water, and mitigates spurious oscillations through a new stabilisation approach for the velocity. Robustness of soil-water interface is achieved by combining nodal-based, free-surface detection, suited for higher-order spline functions with smooth porosity-permeability transitions that avoid constitutive divergence at sharp material boundaries. Validation against laboratory benchmark cases reported in the literature, including pure-water dam break, dam-break seepage through a porous barrier, two granular-collapse tsunami experiments, and a dam-break wave over a movable granular bed, shows accurate and stable free-surface evolution, pressure time histories, seepage fronts, and wave-gauge records. Using an advanced critical-state soil model (NorSand) further improves the reproduction of granular flow kinematics. The results demonstrate that the proposed formulation is a reliable and computationally efficient tool for geotechnical hazards involving intense soil-water coupling, seepage, sediment transport and free water.

math.NA↗

arXiv2026

Study of Landslides through a Stabilised Semi-Implicit Material Point Method

In this research, a new semi-implicit two-phase double-point material point method is proposed, in which the soil and water phases are modelled using two distinct sets of material points, both being stabilised with a novel approach. The Nor-Sand constitutive model is implemented to simulate more realistic soil behaviour. Some landslide numerical examples are presented to investigate the performance of the proposed method and highlight the importance of using the double-point approach. The formulation with two sets of material points shows significantly different but more reliable results in the cases of landslides, compared with the conventional single-point approach. Furthermore, this research shows that the additional computational cost given by the additional water material points is acceptable. Therefore, it is recommended to use two sets of material points for some large deformation geotechnical problems.

math.NA↗

arXiv2025

A Stabilised Semi-Implicit Double-Point Material Point Method for Soil-Water Coupled Problems

A semi-implicit two-phase double-point Material Point Method (MPM) formulation, based on the incremental fractional-step method to model large deformation geotechnical problems has been derived. The semi-implicit formulation has two advantages compared with the explicit approach: the time step is independent of the water phase, and the pore pressure field is more stable. The semi-implicit MPM models based on the incremental fractional-step method available in the literature consist of modelling the soil and water mixture using a single set of material points only, in order to save computational time. In this study, we further derive this formulation with two sets of material points to represent the soil and water phases separately. The stress oscillations that are frequently found in the water and soil phases are stabilised with this approach. A new stabilisation method is developed based on the modified F-bar method. The proposed method is validated with two numerical examples under small and large deformations, respectively. After that, Nor-Sand constitutive soil model is used to simulate landslides. Numerical examples show an excellent performance of the proposed coupled MPM and the stabilisation method. The formulation with two sets of material points yields significantly different but more reliable results in the landslides analysis, compared with the single-point approach. Additionally, this research shows that the additional computational cost caused by the additional water material points is acceptable. Therefore, it is recommended to use two sets of material points for certain large deformation geotechnical problems.

math.NA↗

arXiv2023

Multi-Agent Join

It is crucial to provide real-time performance in many applications, such as interactive and exploratory data analysis. In these settings, users often need to view subsets of query results quickly. It is challenging to deliver such results over large datasets for relational operators over multiple relations, such as join. Join algorithms usually spend a long time on scanning and attempting to join parts of relations that may not generate any result. Current solutions usually require lengthy and repeated preprocessing, which is costly and may not be possible to do in many settings. Also, they often support restricted types of joins. In this paper, we outline a novel approach for achieving efficient join processing in which a scan operator of the join learns during query execution, the portions of its relations that might satisfy the join predicate. We further improve this method using an algorithm in which both scan operators collaboratively learn an efficient join execution strategy. We also show that this approach generalizes traditional and non-learning methods for joining. Our extensive empirical studies using standard benchmarks indicate that this approach outperforms similar methods considerably.

cs.DB↗