Abstract
In this paper, the energy instability criterion of water-resistant strata and rock mass failure index (RMFI) are proposed, respectively, based on releasable elastic strain energy Ue. RMFI is employed to represent the damage extent of water-resistant strata. When RMFI<1.0, rock mass is stable. When RMFI=1.0, rock mass is in the critical instability state. When RMFI>1.0, rock mass is unstable. The releasable elastic strain energy Ue and RMFI program is performed by FISH programming language of Flac3D software. Then, the authors apply Flac3D software to analyze the distribution law of releasable elastic strain energy Ue and failure zone under different width of concealed karst cave. Finally, combined with the numerical analysis, a case study is carried out to illustrate the rationality, effectiveness, and feasibility through using RMFI to predict safe thickness of water-resistant strata.
Highlights
In practical engineering, most water inrush and mud burst disaster in karst tunnel is caused by insufficient safety thickness of water-resistant strata between concealed karst cave and tunnel [1,2,3]
The numerical simulation method Flac3D software can be applied, and the instability discrimination program of water-resistant strata based on releasable elastic strain energy Ue and rock mass failure index (RMFI) is compiled by FISH programming language in Flac3D software
The paper takes some influence factors of the karst cave span D as an example and analyzes the stability of the water-resistant strata and the distribution law of damage area, which is based on releasable elastic strain energy and RMFI
Summary
Most water inrush and mud burst disaster in karst tunnel is caused by insufficient safety thickness of water-resistant strata between concealed karst cave and tunnel [1,2,3]. It is more conductive to reflect the essential characteristics of karst tunnel rock mass global failure through researching energy change law during deformation and failure process of karst limestone and the instability criterion of water-resistant strata based on releasable elastic strain energy. If the instability criterion program of water-resistant strata based on releasable elastic strain energy is embedded into the numerical analysis software, it can get the scope of the damage zone, and obtain the damage degree and the change law of each point. The safety thickness of the water-resistant strata is determined though analyzing the stability of the karst tunnel based on the releasable elastic strain energy, which is of great theoretical significance and engineering application value in guiding the design and construction, preventing the tunnel water inrush and mud burst disaster and ensuring the construction safety. Academician Xie et al give the global failure criterion of rock mass unit [14], which is elaborated as follows
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