The failure process of high stress rock with through-water disturbance based on acoustic emission

Abstract

In the process of deep engineering excavation, the mechanical properties of rock are significantly influenced by the coupled effects of water and high stress, which greatly increase construction difficulty. To more accurately investigate the impact of water disturbance on the failure process of dry rock under high stress and the failure mechanisms of saturated rock in underwater environments, a water environment test chamber and a prefabricated borehole specimen through-water device were designed. A series of experiments were conducted, including uniaxial tests, water-disturbed granite cylinder tests, and through-water disturbance tests on prefabricated hole square specimens. The results showed that the acoustic emission (AE) hits and accumulated energy after the through-water disturbance at the same time were 8.77 and 12.08 times higher than before the disturbance, respectively. And water disturbance increased the proportion of tensile failure and reduced the proportion of shear failure. A key observation was that AE events were mainly generated in the permeation areas near the borehole. The main reason was that under high stress, the weakening effect of water led to the failure of the local mineral structure of the rock, promoting crack extension and triggering overall instability. Notably, failure of the saturated specimens underwater was only observed when the applied load approached the saturation strength of the prefabricated hole square specimens. The study results provide an important theoretical basis for understanding the damage mechanism of water-disturbed rocks in deep engineering, and have significant implications for the design and construction of engineering.

1. Introduction

Water is a key factor in rock stability [1–4], and can significantly change the physical and mechanical properties of rocks, triggering a series of engineering geological hazards, especially the collapse of deeply buried tunnels, the instability of steep slopes, and the surge of water in mines under high stress [5–9]. Therefore, an in-depth discussion of the effect of water on the failure of deeply buried, high-stress rock cannot only provide a scientific basis for the project's construction but also provide an important guarantee for enhancing the overall safety and sustainable development of deep rock engineering.

The coupling of water and high stresses in rock during the excavation of deeply buried rock bodies is a complex problem [10–13]. The effect of this coupling on the mechanical properties of rocks has been studied extensively by many scholars. For example, Li et al. [14], Masoumi et al. [15], and Zhao et al. [16] obtained sandstones with different water contents by soaking sandstones in water for different periods and found that water content was negatively correlated with sandstone strength. Zhu et al. [17] and Chen et al. [18] conducted mechanical tests on granite and found that water significantly reduced mechanical parameters such as uniaxial compressive strength (UCS), modulus of elasticity, and critical strain. Zhu et al. [19] explored the effect of water on marble and found that UCS and modulus of elasticity decreased, while Poisson's ratio increased with increasing water content. Additionally, water significantly affects the short-term mechanical properties of other rocks, such as shale [20], tuff [21], and artificial porous rock [22]. Beyond short-term mechanical property testing, the long-term mechanical properties of rocks are also a hot topic.