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On Criterion for Tunnel Rock Mass Slippage along a Structure Surface and Its Impact Factors
(Key Laboratory of Transportation Tunnel Engineering of Ministry of Education, School of Civil Engineering, Southwest Jiaotong University, Chengdu 610031)
Abstract Based on the continuity hypothesis and Mohr-Coulomb criterion, a criterion to evaluate whether rock mass slippage along a structure surface will occur or not is proposed for a circular tunnel adopting the elastic mechanics method, and the minimum slippage zones of the rock mass under different internal friction angels of the structural surface are predicted. The proposed criterion is verified by the shear displacements of the rock mass along the structural surface with different internal friction angles through UDEC. The impact factors on the minimum internal friction angle to keep the rock mass stable and prevent slippage—including the lateral pressure coefficient, dipangle of the structural surface and the vertical distance from the tunnel center to the structural surface—and the mathematical relation among them are determined, and the impact law for the three factors on the minimum internal friction angle is analyzed. The results show the lateral pressure coefficient, the dip angle of the structural surface mainly influence the minimum internal friction angle of the structural surface that is far from the tunnel and required by keeping the rock mass stable, and the vertical distance only effects the minimum internal friction angle of the structural surface close to the tunnel excavation boundary but has no obvious effect on the region at a distance of more than 2.5 times the excavation radius.
Abstract：
Based on the continuity hypothesis and Mohr-Coulomb criterion, a criterion to evaluate whether rock mass slippage along a structure surface will occur or not is proposed for a circular tunnel adopting the elastic mechanics method, and the minimum slippage zones of the rock mass under different internal friction angels of the structural surface are predicted. The proposed criterion is verified by the shear displacements of the rock mass along the structural surface with different internal friction angles through UDEC. The impact factors on the minimum internal friction angle to keep the rock mass stable and prevent slippage—including the lateral pressure coefficient, dipangle of the structural surface and the vertical distance from the tunnel center to the structural surface—and the mathematical relation among them are determined, and the impact law for the three factors on the minimum internal friction angle is analyzed. The results show the lateral pressure coefficient, the dip angle of the structural surface mainly influence the minimum internal friction angle of the structural surface that is far from the tunnel and required by keeping the rock mass stable, and the vertical distance only effects the minimum internal friction angle of the structural surface close to the tunnel excavation boundary but has no obvious effect on the region at a distance of more than 2.5 times the excavation radius.
2017, Vol. 54 