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Calculation Method for Safe Thickness of Water Insulation Rock in Tunnelling Based on Timoshenko Beam Theory
(1. National Engineering Research Center of High-speed Railway Construction Technology, Central South University,Changsha 410075; 2. China Railway Group Limited, Beijing 100039; 3. School of Civil Engineering, Central South University,Changsha 410075; 4. No.4 Engineering Co., Ltd. of China Railway 17th Bureau Group Co., Ltd., Chongqing 401121)
Abstract Considering the bending effect and the shear effect of the water insulation rock mass around the tunnel under the pressure of the mud water in the karst cavity, an analytical calculation model of the safe thickness of the water insulation rock of the tunnel is established based on the Timoshenko beam theory, the calculation method of the minimum safe thickness is derived as per the flexural strength criterion and the shear strength criterion, and the influencing factors of the analytical model for the safe thickness of the water insulation rock are systematically analyzed based on project cases. The results indicate that the diameter of the karst cavity has the most significant impact on the minimum safe thickness of the water insulation rock. The minimum safe thickness of the water insulation rock increases with the rise of tunnel burial depth, cavity diameter, and cavity water pressure. With the increase of tunnel burial depth and water pressure in the karst cavity, the water insulation rock is more prone to bending failure compared with shear failure. As the azimuth angle of the karst cavity increases, the minimum safe thickness of the water insulation rock first decreases and then increases, the rate of reduction first increases and then slows down, the maximum safe thickness value occurs when the karst cavity is located at the top of the tunnel, and there is the minimum safe thickness value when the karst cavity is located at the bottom of the tunnel. Compared with existing researches,it is found that the calculation method for the minimum safe thickness of water insulation rock, in which the impact of both bending and shear effects of rock beam is considered, can more effectively reflect the deformation characteristics of rock beams between the karst cavity and the tunnel, and is of good practicality.
Abstract：
Considering the bending effect and the shear effect of the water insulation rock mass around the tunnel under the pressure of the mud water in the karst cavity, an analytical calculation model of the safe thickness of the water insulation rock of the tunnel is established based on the Timoshenko beam theory, the calculation method of the minimum safe thickness is derived as per the flexural strength criterion and the shear strength criterion, and the influencing factors of the analytical model for the safe thickness of the water insulation rock are systematically analyzed based on project cases. The results indicate that the diameter of the karst cavity has the most significant impact on the minimum safe thickness of the water insulation rock. The minimum safe thickness of the water insulation rock increases with the rise of tunnel burial depth, cavity diameter, and cavity water pressure. With the increase of tunnel burial depth and water pressure in the karst cavity, the water insulation rock is more prone to bending failure compared with shear failure. As the azimuth angle of the karst cavity increases, the minimum safe thickness of the water insulation rock first decreases and then increases, the rate of reduction first increases and then slows down, the maximum safe thickness value occurs when the karst cavity is located at the top of the tunnel, and there is the minimum safe thickness value when the karst cavity is located at the bottom of the tunnel. Compared with existing researches,it is found that the calculation method for the minimum safe thickness of water insulation rock, in which the impact of both bending and shear effects of rock beam is considered, can more effectively reflect the deformation characteristics of rock beams between the karst cavity and the tunnel, and is of good practicality.
ZHENG Xiaoyue1,
3 SHI Chenghua1,
2 etc
.Calculation Method for Safe Thickness of Water Insulation Rock in Tunnelling Based on Timoshenko Beam Theory[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(4): 14-22
2023, Vol. 60 