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Study on Drainage Schemes for Karst Tunnels Based on Hydraulic Pressure
Characteristics
(1. School of Civil Engineering, Southwest Jiaotong University , Chengdu 610031; 2. State Key Laboratory of Intelligent Geotechnics and Tunnelling, Southwest Jiaotong University, Chengdu 610031; 3. China Railway 11th Bureau Group Co., Ltd., Wuhan 430061)
Abstract The water pressure on the lining of in-service karst tunnels is closely related to the drainage design
scheme. Based on the Zhongliangshan Tunnel on the Chongqing-Kunming High-Speed Railway, three improved
drainage schemes were designed on the basis of the general drainage design scheme for mountain tunnels. Treating the karst strata as equivalent homogeneous seepage strata, a three-dimensional numerical simulation was conducted to analyze the water pressure distribution patterns on tunnel lining under the three schemes. Field measurements of water pressure were also performed. The results reveal the following: (1) For weakly developed karst tunnels, under normal drainage conditions, water pressure at the crown and haunch of the tunnel lining can be significantly reduced, but the sidewall, wall-foot, and invert arch still bear substantial water pressure; (2) Along the longitudinal direction of the tunnel, the water pressure on all measuring lines of the lining exhibits an "M"-shaped distribution,with the lowest pressure at the circumferential drainage pipes and higher pressure between two circumferential drainage blind pipes; (3) In terms of reducing water pressure on the invert arch, the scheme with a bottomed central drainage ditch is the most effective, followed by the scheme with additional dense drainage holes in the invert arch,
while the scheme with only circumferential drainage blind pipes in the invert arch performs the worst; (4) Considering both water pressure reduction effectiveness and construction quality, it is recommended that the weakly developed karst sections of the Zhongliangshan Tunnel adopt a scheme with circumferential drainage blind pipes in the invert arch and additional drainage holes in the invert arch and wall-foot; (5) Monitoring results of water pressure on invert arch show significant fluctuations influenced by surface rainfall. The measured water pressure and distribution on invert arch closely match the numerical simulation results, validating the effectiveness of the recommended drainage scheme.
Abstract：
The water pressure on the lining of in-service karst tunnels is closely related to the drainage design
scheme. Based on the Zhongliangshan Tunnel on the Chongqing-Kunming High-Speed Railway, three improved
drainage schemes were designed on the basis of the general drainage design scheme for mountain tunnels. Treating the karst strata as equivalent homogeneous seepage strata, a three-dimensional numerical simulation was conducted to analyze the water pressure distribution patterns on tunnel lining under the three schemes. Field measurements of water pressure were also performed. The results reveal the following: (1) For weakly developed karst tunnels, under normal drainage conditions, water pressure at the crown and haunch of the tunnel lining can be significantly reduced, but the sidewall, wall-foot, and invert arch still bear substantial water pressure; (2) Along the longitudinal direction of the tunnel, the water pressure on all measuring lines of the lining exhibits an "M"-shaped distribution,with the lowest pressure at the circumferential drainage pipes and higher pressure between two circumferential drainage blind pipes; (3) In terms of reducing water pressure on the invert arch, the scheme with a bottomed central drainage ditch is the most effective, followed by the scheme with additional dense drainage holes in the invert arch,
while the scheme with only circumferential drainage blind pipes in the invert arch performs the worst; (4) Considering both water pressure reduction effectiveness and construction quality, it is recommended that the weakly developed karst sections of the Zhongliangshan Tunnel adopt a scheme with circumferential drainage blind pipes in the invert arch and additional drainage holes in the invert arch and wall-foot; (5) Monitoring results of water pressure on invert arch show significant fluctuations influenced by surface rainfall. The measured water pressure and distribution on invert arch closely match the numerical simulation results, validating the effectiveness of the recommended drainage scheme.
ZHAO Dongping1,
2 HE Qi1 DU Qing3 ZHANG Wen3
.Study on Drainage Schemes for Karst Tunnels Based on Hydraulic Pressure
Characteristics[J] MODERN TUNNELLING TECHNOLOGY, 2024,V61(6): 162-717
2024, Vol. 61 