Abstract
The problem of shaft instability has always been a major difficulty in deep mining practices. The shaft fracture has a high probability of being located near the aquifers and the soft–hard rock contact zone. This paper describes the deformation and stress characteristics of surrounding rock and the shaft lining under the interactive geological conditions under soft and hard rock strata in Anju coal mine, Shandong Province, China. Using the Method of Geological Strength Index (GSI ) and considering the rock-softening characteristics of water, the parameters of rock mass are calibrated. By means of the 3DEC-trigon method, the variation characteristics of surrounding rock and the shaft lining are simulated. After shaft excavation, under the condition of no support, shear failure and tensile failure occur in shallow surrounding rock shafts, and a pressure relief zone is formed. Shear failure is the main destruction mode in deep surrounding rock. Because of the different strengths of the surrounding rock, the deformation of the surrounding rock is significantly different. After the surrounding rock is softened by water absorption, the difference is magnified. The maximum shear stress and plastic zone appear near the interface between soft and hard rock. Under the condition of shaft lining support, uneven deformation of surrounding rock surely leads to nonlinear variation of pressure on the shaft lining. Under the action of an inhomogeneous pressure field, partial shear failure occurs in the shaft lining, and the shear failure area increases after the surrounding rock is softened by water. Because of the nonlinear deformation of the shaft lining, it is easy to produce stress concentration and bending moment near the interface between hard and soft strata. The control methods of advance grouting and pressure relief excavation are proposed to improve the stability of the shaft, and a good effect is gained.
Highlights
As the coal resource has been exhausted in shallow mining areas, deep mining has become increasingly common, and the depth of the mine shaft has increased greatly
Through a large number of investigations on shaft rupture in the Huang Huai area, Wang J et al [2] opined that the of shaft fractures is mostly near and the aquifers andzone the of contact zone of soft rock of location shaft fractures is mostly located nearlocated the aquifers the contact soft rock interlaced with interlaced with hard rock
This paper presents a numerical simulation study on the deformation mechanism of surrounding This paper presents a numerical simulation study on the deformation mechanism of rock, and the stress characteristics of the shaft lining, in alternating hard and soft rock strata
Summary
As the coal resource has been exhausted in shallow mining areas, deep mining has become increasingly common, and the depth of the mine shaft has increased greatly. The phenomenon of shaft fracture has occurred frequently and caused serious damage and great loss to coal mine enterprises, and it has restricted deep mine mining. There are mainly five hypotheses on the mechanism of shaft failure of coal hard rock. The mechanism of thethe failure of a deep shaft in the ofsoft–hard a deep shaft in the soft–hard rock interface is still unclear and less studied. Yidong main shaft failures occurred near the interface of strata. In the process of reasonable parameter selection, rock based on a case study at AN JU mine shaft.
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