Model tests and numerical simulations on hydraulic fracturing and failure mechanism of rock landslides

Abstract

Hydraulic fracturing (HF) is a physical phenomenon of the initiation, propagation and penetration of micro fractures in rocks under high water pressure until generate macro fractures, which is an important reason for inducing rock landslides. The in uences of the angle between the transverse pressure stress and the initial fracture, the transverse pressure stress, the length and aperture of the initial fracture on the critical water pressure stress of HF were analyzed based on the model tests of cement mortar specimens. The HF numerical simulations were carried out and the fracture aperture, pore pressure, strain and stiffness degradation index were analyzed based on ABAQUS software, and the HF mechanism of rock was revealed. Taking a rock slope along Letuan-Qingshiguan section of G205 in China as an example, the landslide stability under high groundwater pressure was studied by numerical simulations, and the whole processes of the expansion, propagation, penetration and the rock slope failure were reproduced. The results showed that when HF occurred on the cement mortar specimens, a large amount of water seeped from the fracture and made a dull sound of failure, the water pressure on the fracture plane decreased rapidly, but not completely penetrated, and there was still a certain residual strength of the specimen. The water ow in the fracture has dual mechanical effects on the fracture wall. The HF of rock (including cement mortar specimen) is a quasi-brittle failure, including static stage, micro fracture propagation stage and macro fracture formation stage. There are 3 dangerous rocks in the rock slope, among which WYT3 is in a stable state under the natural condition and in unstable states under the rainstorm condition and seismic condition. The fracture propagation of WYT3 under the action of high groundwater pressure experienced slow development stage, rapid development stage and penetration stage, among which the slow development stage lasted the longest, and the slope failure occurred immediately after the fracture penetrated (i.e., rock landslide occurred).