Topic：Hydrodynamics of landslides and debris flows

Time:15:00-17:00 p.m.,May 12,2018

Place:An-zhong Conference Hall

Reporter:Prof. Ronaldo I. Borja

Introduction to the report：

Rainfall and earthquakes weaken an earth slope in many ways. In partially saturated slopes, rainfall increases the degree of saturation of a soil, thereby breaking the bonds created by surface tension between soil particles. When the volume of infiltrating water is large enough to mobilize fluid flow inside the soil matrix, a downhill frictional drag is exerted by the fluid on the sediment, creating a destabilizing effect on the slope. In fully saturated slopes, or even when the degree of saturation is not exactly 100 percent in the soil, an earthquake could cause momentary pore pressure buildup and reduce the frictional strength of the soil. Furthermore, the inertia load generated by an earthquake creates an additional demand that could test the capacity of the soil to resist failure. In this talk, he will present a physics-based framework for continuum modeling of slope failure induced either by an earthquake or by rainfall. His talk will focus on both the triggering mechanisms leading to slope failure, and the subsequent flow mechanisms characterizing the movement of earth materials at post-triggering. He will also discuss the potential of the finite element method and a meshless method called smoothed particle hydrodynamics (SPH) for capturing the triggering and post-triggering failure mechanisms in earth slopes, including that of debris flows.

Introduction to  the reporter:

Professor Ronaldo  I. Borja works in theoretical and computational solid mechanics, geomechanics, and geosciences. At Stanford University, he teaches an undergraduate course in geotechnical engineering, a graduate course in mechanics and the finite element method, and two doctoral level courses in computational plasticity and computational poromechanics. His research includes the development of multi-scale discontinuity framework for crack and fracture propagation utilizing the strong discontinuity and extended finite element methods; solution techniques for multi-physical processes such as coupled solid deformation-fluid diffusion in saturated and unsaturated porous media; stabilized finite element methods for solid/fluid interaction and nonlinear contact mechanics; and nanometer-scale characterization of the inelastic deformation and fracture properties of shales. Professor Borja is the author of a textbook entitled Plasticity Modeling & Computation published by Springer. He serves as editor of two leading journals in his field, the International Journal for Numerical and Analytical Methods in Geomechanics published by Wiley, and Acta Geotechnica published by Springer. Professor Borja is the recipient of the 2016 ASCE Maurice A. Biot Medal for his work in computational poromechanics.