Three-dimensional numerical modeling of water distribution tunnels in karst area
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ORIGINAL PAPER
Three-dimensional numerical modeling of water distribution tunnels in karst area Xiao-dong Pan 1 & Yu-chao Fang 1 & Yong Lai 2 & Hong-lei Sun 1 & Yuan-qiang Cai 1 & Li Shi 1 & Xue-yu Geng 3 Received: 23 July 2019 / Accepted: 29 July 2020 # Saudi Society for Geosciences 2020
Abstract Karst physiognomy is a common terrain in mountainous area. The tunnels constructed through these terrains may suffer from stress maldistribution due to the existence of the karst caves. The lining of water distribution tunnels passing through karst caves suffer from both the outer pressure of surrounding rock and the inner water pressure that could cause cracks of the lining and seepage of the water. This study focuses on the influence of exposed karst caves on water distribution tunnels. In order to assess the risks caused by the karst caves, finite element methods are carried out. Test datum of the tunnel in the Water Distribution Project of Qiandao Lake is used to validate the accuracy of the FEM model. The effects of filling the karst cave with concrete and embedding pre-stress steel strands into the lining are studied, respectively. Results show that filling the karst cave with concrete grout can eliminate the inhomogeneity of the tensile stress of the lining, and embedding the pre-stress steel strands into the lining can resist the inner water pressure effectively. Meanwhile, the most appropriate pre-stressing force and the relationship between the pre-stressing force and the inner water pressure are suggested. Keywords Karst cave . Numerical analysis . Contact length . Pre-stress steel strand
Introduction Engineering problems caused by karst caves are common in the construction of tunnels. Both concealed and exposed karst caves are hazardous to the tunnels. As a big void with karst water, the existence of a karst cave can influence the stress state of the tunnels and cause disasters such as lining crack and water seepage (Huang et al. 2018). Most existing studies of the karst tunnels focus on the prediction of karst caves. Zhang et al. (2018) evaluated the underground karst state by using a fuzzy assessment system. The system can make the prediction more efficient and accurate. Wang and Sun (2006) established a forecast model of the safe
Responsible Editor: Zeynal Abiddin Erguler * Hong-lei Sun [email protected] 1
College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou, China
2
Zhejiang Design Institute of Water Conservancy and Hydroelectric Power, Hangzhou, China
3
School of Engineering, University of Warwick, Coventry, UK
thickness of the karst cave floor based on a practical karst tunnel cases. By using multiple regressions and the support vector machine (SVM) method, the model comprehensively reflected the shape of the karst and property of surrounding rock. In order to reliably predict the state of collapse in tunnels and cavities, Fraldi and Guarracino (2009; Lippmann 1971) presented an exact solution in the realm of plasticity theory. The method is proposed as
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