Abstract
From the point of view of the failure mechanism of the disturbed zone, this paper uses the limit analysis upper-bound theory to analyze the calculation formula of the loosening pressure, distinguish the difference between the vertical pressure and the horizontal pressure in the underground cavern, combine the loosening characteristics of the disturbed zone with the open-type disturbed zone and the annular disturbed zone, and construct the multirigidity slider translation and rotation failure mode to discuss the calculation method of surrounding rock loosening pressure of underground caverns in upper soft and hard rock stratum. The relevant calculation examples are given, and the application of the upper-bound theory of limit analysis is demonstrated in detail. Based on the actual engineering background, the calculation results of the calculation method of the loosening pressure of the cavity based on the upper-bound theory of the limit analysis are analyzed and compared for the different depths and different types of caverns. The difference, rationality, and applicability of the calculation results of this method are analyzed and discussed.
Highlights
When calculating the loose surrounding rock pressure of an underground cavern in a rock mass with joints, the influence of the distribution characteristics and mechanical properties of various structural surfaces in the rock mass on the shape and size of the loose zone around the underground cavern will be ignored, which will make the calculation result produce a large deviation. erefore, for underground caverns in jointed rock masses, it has become an urgent problem to study the surrounding rock deformation and failure mechanisms that can reflect the actual characteristics of the rock mass and to develop a more reasonable method for calculating the loosening pressure of surrounding rock masses
The commonly used analytical calculation formulas are mostly based on the circular underground cavern model. ese formulas include Fenner’s formula, modified Fenner’s formula, Casaer’s formula, and Caquot’s formula. e objects of calculation are mostly deep underground caverns
In the actual geotechnical engineering, when calculating the problems such as the surrounding rock pressure of the underground cavern, the most concern is not the specific size and distribution of the internal stress field and displacement field of the surrounding rock; usually, only the failure load or stability degree corresponding to the final plastic flow state can be calculated
Summary
When calculating the loose surrounding rock pressure of an underground cavern in a rock mass with joints, the influence of the distribution characteristics and mechanical properties of various structural surfaces in the rock mass on the shape and size of the loose zone around the underground cavern will be ignored, which will make the calculation result produce a large deviation. erefore, for underground caverns in jointed rock masses, it has become an urgent problem to study the surrounding rock deformation and failure mechanisms that can reflect the actual characteristics of the rock mass and to develop a more reasonable method for calculating the loosening pressure of surrounding rock masses. In the actual geotechnical engineering, when calculating the problems such as the surrounding rock pressure of the underground cavern, the most concern is not the specific size and distribution of the internal stress field and displacement field of the surrounding rock; usually, only the failure load or stability degree corresponding to the final plastic flow state can be calculated. Erefore, the maximum load acting on the supporting structure when the surrounding rock reaches the limit state is more concerned in the structural design For such problems, the ultimate load and failure modes corresponding to the failure of reaching the critical state of the rock and soil can be obtained by the method of limit analysis in plastic mechanics [12]. On this basis, according to the law of conservation of work, the virtual work equation and the virtual power equation are established to solve the physical quantity obtained. erefore, for the calculation of surrounding rock pressure in shallow tunnels, the use of the limit analysis method is an effective means
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