Numerical Modeling of Pumping-Induced Earth Fissures Using Coupled Quasi-Static Material Point Method

Abstract

Pumping-induced earth fissuring is a typical fluid–solid coupling problem involving fracture evolution. Despite recent advances in the numerical modeling of earth fissures, a holistic approach capable of predicting their evolution and understanding their behavior from fracture mechanisms is absent. This paper presents a coupled numerical method based on the framework of the material point method (MPM) and fracture mechanics for the process-oriented simulation of pumping-induced tensile earth fissures. In this method, fissure behavior is driven by the real-time stress field affected by soil consolidation. After an earth fissure initiates in the region of maximum tensile stress, it propagates in the direction of the maximum circumferential stress around the fissure tip. The great scale difference between a fissure tip and the entire model is addressed with an adaptive refinement strategy. Through the simulation of a physical model experiment reproducing pumping-induced earth fissures with the presence of a bedrock ridge, the complete fissuring process, including initiation, propagation, and arrest, is presented. The simulated fracture time (24 h after drainage), location (directly above the bedrock ridge), final length (165 mm), and morphology evolution (from straight to zigzag) of the main fissure basically were in agreement with the experimental results. The stress intensity factors (SIFs) around fissure tips, which are important fracture parameters that have not been discussed in existing earth fissure analyses, also are captured during the fissure growth. The proposed method quantifies the inhibition of geostatic stress fields in earth fissure development and correlate fissure morphology with the stress field at a fissure tip.