Study on Fracture and Permeability Characteristics of Unloading Rock with High Water Pressure

Abstract

Research on the damage and seepage characteristics of unloading rock with high water pressure can help to further understand the mechanism of water inrush in deep mine floor and prevent water inrush. This paper used the RFPA2D-flow finite element software to study the failure and seepage characteristics of unloading rock with high water pressure and high stress and comparatively analyzed the failure modes and seepage characteristics of unloading rock with and without water pressure. The effects of different water pressure differences on the failure of unloading rock and the law of seepage were investigated by analyzing the change of acoustic emission and permeability coefficient with stress. The results showed that the unloading rock without water pressure was brittle failure, and the initial damage of the unloading model with water pressure was earlier than that of the model without water pressure and showed greater brittleness, and its cracks first break through at the bottom of the sample with higher osmotic pressure. With the increase in unloading, the permeability of rock increased gradually until it appeared an abrupt change. The failure mode and permeability law of the rock with different water pressure differences were basically the same, but the greater the pressure difference, the smaller the effective unloading capacity when the permeability coefficient changes suddenly, and the greater the possibility of water inrush in the rock.

Effect of Fracture Geometry Parameters on the Permeability of a Random Three-Dimensional Fracture Network

“…In this study, Darcy's law and the cubic law were used to describe the flow of water in pores and fractures, which applies to most rock mass seepage problems. The researchers also introduced a gravity term to consider the effect of gravity on water in fractures [39]. The researchers used power law distribution and Fisher function distribution to describe the distribution characteristics of fracture length, aperture, and angle parameters based on their study of the distribution form of fractures in nature.…”

“…A gravity field was introduced in the model for the experiment. The findings led to the creation of a comprehensive seepage formula for fractured rock masses, offering a reliable tool for predicting and analyzing seepage behavior [39]. This research is crucial for the development and use of groundwater resources, the prevention of groundwater pollution, and the aversion of geological disasters.…”

Prediction of the Long-Term Performance Based on the Seepage-Stress-Damage Coupling Theory: A Case in South-to-North Water Diversion Project in China

“…� 𝒔𝒔 𝒕𝒕 = 𝟏𝟏 − 𝝎𝝎 𝒕𝒕 𝒓𝒓�𝝈𝝈 � � �, 𝟎𝟎 ≤ 𝝎𝝎 𝒕𝒕 ≤ 𝟏𝟏 𝒔𝒔 𝒄𝒄 = 𝟏𝟏 − 𝝎𝝎 𝒄𝒄 �𝟏𝟏 − 𝒓𝒓�𝝈𝝈 � � ��, 𝟎𝟎 ≤ 𝝎𝝎 𝒄𝒄 ≤ 𝟏𝟏 (13) where 𝝎𝝎 𝒕𝒕 and 𝝎𝝎 𝒄𝒄 are the weighting factors of stiffness recovery related to the material properties. Figure 1 shows the stiffness recovery curve of the concrete damage model when the weighting factors are 𝝎𝝎 𝒕𝒕 = 𝟎𝟎 (compression → tension) and 𝝎𝝎 𝒄𝒄 = 𝟏𝟏 (tension → compression) under uniaxial alternating loads.…”

“…They studied the fracturing conditions, fractures' spatial distribution, and the variation law of mud seepage distance. Through analysis and comparison, Ma et al [13] obtained the failure mode and seepage characteristics of unloaded rock with and without water pressure. Ma et al [14] used finite-difference to analyze the influence of saturated or unsaturated seepage on the slope stability.…”