Abstract
To investigate the seepage behavior in karst tunnel surrounding rock, the Yesanguan Tunnel of the Yi-Wan Railway was selected as the engineering case study. Key factors influencing surrounding rock seepage were identified through analysis of engineering data and literature review. An elastic damage-based finite element computational model for karst tunnel seepage was developed using RFPA software to analyze the effects of surrounding rock fracture morphology, permeability coefficient, and water pressure loading rate on seepage characteristics. The results demonstrate that the permeability coefficient, fracture morphology, and water pressure loading rate significantly influence seepage, with their impact diminishing in that order. With increasing water pressure, the evolution of surrounding rock fractures progresses through three distinct stages: a stable latent phase, a sudden failure phase, and an accelerated development phase. Fracture propagation typically occurs divergently from fracture tips along the fracture orientation. Upon reaching a critical water pressure threshold, the number of damaged elements surrounding fracture tips increases dramatically, forming densely interconnected new fractures. This process transforms originally resistant elements into weak elements, ultimately establishing preferential seepage pathways.
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Preamble
Study on Seepage Law of Surrounding Rock of Karst Tunnel Under Different Factors
TIAN Xiaolu (China Railway 16th Bureau Group Fourth Engineering CO. Ltd., Beijing 101400, China)
Abstract
To investigate the seepage law of surrounding rock in karst tunnels, this study takes the Yesanguan Tunnel of the Yiwan Railway as the engineering background. Key factors influencing surrounding rock seepage were identified through analysis of engineering data and literature review. Using RFPA software, a finite element calculation model for karst tunnel seepage was established based on elastic damage theory to analyze the effects of surrounding rock fracture patterns, permeability coefficient, and water pressure loading rate on seepage behavior. The results indicate that these three factors exert significant influence on seepage, with their impacts decreasing in the following order: permeability coefficient, fracture patterns, and water pressure loading rate. As water pressure increases, the fracture evolution process in surrounding rock progresses through three stages: a stable latent stage, a sudden failure stage, and an accelerated development stage. Fracture failure typically propagates divergently from the fracture tip along the fracture orientation. When water pressure reaches a critical threshold, the number of damaged elements around the fracture tip increases sharply, intensifying and interconnecting to form new fractures. This transformation converts originally resistant elements into weak elements, ultimately establishing preferential seepage pathways.
Keywords: Karst tunnel; Influencing factors; Seepage law; Evolution process