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A Study on Reduction Coefficient of External Hydraulic Pressure at the Lining of Diversion Tunnel in Saturated Q2 Loess Stratum
(1.Institute of Geotechnical Engineering, Xi'an University of Technology, Xi′an 710048; 2. Technical Research Center for UrbanGeological and Underground Space Engineering of Shaanxi, Xi′an 710068; 3. China Railway First Survey and Design Institute Group Co., Ltd., Xi′an 710043)
Abstract The value of the reduction coefficient of external hydraulic pressure has a great impact on the design of the lining structure of hydraulic tunnels. This paper is based on the case of a water diversion tunnel crossing Q2 loess stratum and investigates the saturated permeability characteristics of in-situ and remodeled Q2 loess through indoor tests and in-situ pumping tests. Also, the study comparatively investigates the changing pattern of the reduction coefficient of external hydraulic pressure on the lining under different five factors: stratigraphic conditions, limited discharge rate, tunnel size, groundwater level, and thickness of the ground grouting ring, through a model test and according to the principle of flow-solid coupling analysis of the FLAC 3D program. The results show that the increase in the limited discharge rate of the tunnel and the thickness of the grouted reinforcement ring will significantly reduce the reduction coefficient of external hydraulic pressure at the lining, and the increase in the permeability coefficient of the ground will cause an increasing trend that follows a logarithmic function for the reduction coefficient of external hydraulic pressure. Also, as the equivalent radius of the tunnel increases, the reduction coefficient of the external hydraulic pressure decreases before an increase, while the groundwater level has an insignificant effect on the reduction coefficient of the external hydraulic pressure. For this project, it is recommended to take the value of 0.57~0.71 for the reduction coefficient of the external hydraulic pressure.
Abstract：
The value of the reduction coefficient of external hydraulic pressure has a great impact on the design of the lining structure of hydraulic tunnels. This paper is based on the case of a water diversion tunnel crossing Q2 loess stratum and investigates the saturated permeability characteristics of in-situ and remodeled Q2 loess through indoor tests and in-situ pumping tests. Also, the study comparatively investigates the changing pattern of the reduction coefficient of external hydraulic pressure on the lining under different five factors: stratigraphic conditions, limited discharge rate, tunnel size, groundwater level, and thickness of the ground grouting ring, through a model test and according to the principle of flow-solid coupling analysis of the FLAC 3D program. The results show that the increase in the limited discharge rate of the tunnel and the thickness of the grouted reinforcement ring will significantly reduce the reduction coefficient of external hydraulic pressure at the lining, and the increase in the permeability coefficient of the ground will cause an increasing trend that follows a logarithmic function for the reduction coefficient of external hydraulic pressure. Also, as the equivalent radius of the tunnel increases, the reduction coefficient of the external hydraulic pressure decreases before an increase, while the groundwater level has an insignificant effect on the reduction coefficient of the external hydraulic pressure. For this project, it is recommended to take the value of 0.57~0.71 for the reduction coefficient of the external hydraulic pressure.
ZHU Caihui1,
2 YING Li2 YANG Qiqiang2 LI Yubo3
.A Study on Reduction Coefficient of External Hydraulic Pressure at the Lining of Diversion Tunnel in Saturated Q2 Loess Stratum[J] MODERN TUNNELLING TECHNOLOGY, 2023,V60(2): 94-102
2023, Vol. 60 