Study of the function of the insulation layer for treating water leakage in permafrost tunnels

Abstract

Qinghai–Tibet Railway is one of the national momentous construction projects in the West Development Plan of China. Kunlun mountain tunnel is the key control engineering of the railway. But, according to the observation in-situ data, on May 22, 2003, water irruption took place in the construction joints at DK977 + 620 section (the sign DK is an abbreviation of distance kilometer, the number 977 expresses the 977 km, and the number 620 expresses 620 m), and the maximum flux of the water reached to about 200 m 3/d(1 m 3/d means one cubic meter per day), and the water pressure increased violently. In this paper, the status of water leakage of Kunlun mountain tunnel on Qinghai–Tibet railway is introduced by the time step. Based on the status of water leakage, the reason for water leakage in the tunnel is opened out. According to the basal theories of heat transfer and seepage, considering the coupled effect of seepage field and temperature field, a three-dimensional calculational model of the coupled problem are given, and the finite element formulae are obtained by Galerkin’s method, and the computer program is written. Using this model and program, three-dimensional nonlinear analysis for the coupled problem of the flat buried part from DK977 + 578 to DK977 + 682 in Kunlun mountain tunnel on Qinghai–Tibet Railway are made either with or without the insulation layer. The result shows that it is necessary for treating water leakage to fit the insulation layer between the two linings in Kunlun mountain tunnel.