Abstract
With the increase in shaft depth, the problem of cracks and leakage in single-layer concrete lining in porous water-rich stable rock strata has become increasingly clear, in which case the mechanism of fracturing in shaft lining remains unclear. Considering that the increase in pore water pressure can cause rock mass expansion, this paper presents the concept of hydraulic expansion coefficient. First, a cubic model containing spherical pores is established for studying hydraulic expansion, and the ANSYS numerical simulation, a finite element numerical method, was used for calculating the volume change of the model under the pore water pressure. By means of the multivariate nonlinear regression method, the regression equation of the hydraulic expansion coefficient is obtained. Second, based on the hydraulic expansion effect on the rock mass, an interaction model of pore water pressure–porous rock–shaft lining is established and further solved. Consequently, the mechanism of fracturing in shaft lining caused by high-pressure pore water is revealed. The results show that the hydraulic expansion effect on the surrounding rock increases with its porosity and decreases with its elastic modulus and Poisson’s ratio; the surrounding rock expansion caused by the change in pore water pressure can result in the outer edge of the lining peeling off from the surrounding rock and tensile fracturing at the inner edge. Therefore, the results have a considerable guiding significance for designing shaft lining through porous water-rich rock strata.
Highlights
In recent years, with the implementation of China’s western development strategy, the abundant coal resources in some water-rich bedrock areas (Shaanxi, Ningxia, Gansu, Inner Mongolia, etc.) have been mined on a large scale [1]
The results show that the hydraulic expansion effect on the surrounding rock increases with its porosity and decreases with its elastic modulus and Poisson’s ratio; the surrounding rock expansion caused by the change in pore water pressure can result in the outer edge of the lining peeling off from the surrounding rock and tensile fracturing at the inner edge
Based on the cubic model of hydraulic expansion containing a spherical pore, its volume change is calculated by the ANSYS numerical simulation, and the approximate analytical solution of the hydraulic expansion coefficient is obtained by the multivariate nonlinear regression method
Summary
With the implementation of China’s western development strategy, the abundant coal resources in some water-rich bedrock areas (Shaanxi, Ningxia, Gansu, Inner Mongolia, etc.) have been mined on a large scale [1]. Regarding the study topic on hydrophobic settlement, Lou [7] derived a general formula for calculating the additional stress in the shaft lining based on the drainage consolidation theory. Some existing theories have matured, the fracture mechanism of shaft lining in high-pressure water-rich stable rock strata has not been clarified. Based on the compressive and expansive deformation properties of the porous media under the action of stress, in analogy with the coefficient of thermal expansion, this paper defines the linear expansion coefficient of the rock caused by unit pore water pressure as the hydrostatic expansion coefficient, which is expressed as α. By comprehensively analyzing the influence of various factors on the shaft lining stress, the mechanism of fracturing in shaft lining due to high-pressure pore water is clarified, providing an effective and scientific basis for lining safety
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