Abstract
Wetting-drying alternation caused by seasonal rainfall and water fluctuation has a negative effect on the rock mass. Model experiments were conducted in this paper to investigate the role of wetting-drying alternation on the seepage and failure features of a tunnel. Water-bearing structure was located in the lateral position of tunnel. The stratum thickness between the tunnel and water-bearing structure was ranged from 20 to 100 mm. The results showed that, with an increase in the wetting-drying alternation number, the pore water pressure increases gradually. The critical water pressure also increases gradually with the increasing thickness of water-resisting stratum. With the increase of the stratum thickness, the permeable area is gradually widened and the water storage capacity becomes stronger. The failure mode of water-resisting stratum under geostress and water pressure can be summarized as two types: fracture failure (thickness of 20 mm) and slippage failure (thickness between 40 and 100 mm), respectively.
Highlights
With the vigorous development of economics, the focus of major engineering construction has shifted from plains to the mountainous and karst areas with extremely complex topographic and geological conditions
The whole process of the variation of pore water pressure can be divided into four stages: rising stage, unstable stage, stable stage, and declining stage
The pore water pressure increases dramatically, which indicates that the surrounding rock of the tunnel is sensitive to the increment of the groundwater level
Summary
With the vigorous development of economics, the focus of major engineering construction has shifted from plains to the mountainous and karst areas with extremely complex topographic and geological conditions. Xu et al [12] investigated the minimum safety thickness of the rock resisting water inrush from filling-type karst caves located in the top, bottom, and lateral positions to the tunnel. Based on the Yuelongmen tunnel of Chengdu to the Lanzhou railway line in China, Jiang et al [13] carried out a series of large-scale geomechanical model tests to study the effect of waterproof-resistant slab thickness of surrounding rock on water inrush disaster and established a simplified model to simulate the whole disaster process. In order to investigate the characteristics of water inrush and instability modes of the tunnel under the influence of wetting-drying alternation, large-scale geomechanical models were set up based on the engineering geological background of the Liupanshan tunnel. The effects of stratum thickness on the seepage and failure modes of surrounding rock were analyzed
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