Study on mechanism of macro failure and micro fracture of local nearly horizontal stratum in super-large section and deep buried tunnel
Shu-cai Li,Jian-hua Wang,Wei-zhong Chen,Li-ping Li,Qian-qing Zhang,Peng He
Abstract
The stability of surrounding rock will be poor when the tunnel is excavated through nearly horizontal stratum. In this paper, the instability mechanism of local nearly horizontal stratum in super-large section and deep buried tunnel is revealed by the analysis of the macro failure and micro fracture. A structural model is proposed to explain the mechanics of surrounding rock collapse under the action of stress redistribution and shed light on the macroscopic analytical approach of the stability of surrounding rock. Then, some highly effective formulas applied in the tunnel engineering are developed according to the theory of mixed-mode micro fracture. And well-documented field case is made to demonstrate the effectiveness and accuracy of the proposed analytical methods of mixed-mode fracture. Meanwhile, in order to make the more accurate judgment about yield failure of rock mass, a series of comprehensive failure criteria are formed. In addition, the relationship between the nonlinear failure criterion and KI and KII of micro fracture is established to make the surrounding rock failure criterion more comprehensive and accurate. Further, the influence of the parameters related to the tension-shear mixed-mode fracture and compressionshear mixed-mode fracture on the propagation of rock crack is analyzed. Results show that σ3 changes linearly with the change of σ1. And the change rate is related to β, angle between the cracks and σ1. The proposed simple analytical approach is economical and efficient, and suitable for the analysis of local nearly horizontal stratum in super-large section and deep buried tunnel.
(1) Shu-cai Li, Jian-hua Wang, Wei-zhong Chen, Li-ping Li, Qian-qing Zhang, Peng He — Research Center of Geotechnical and Structural Engineering, Shandong University, Ji'nan 250061, Shandong, China
(2) Wei-zhong Chen — State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, Hubei, China.
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