| The cold permafrost tunnel will encounter frozen-heave damage and thaw damage in construction and operation. In this paper, thawing settlement of tunnel engineering in permafrost regions is studied. Thawing settlement deformation and heat harm treatment measures are studied through theoretical analysis and numerical simulation methods,empirical induction. The results obtained are as follows.1. The temperature change function of the center point of a section of the tunnel under the 2 years construction conditions and the temperature change function at the center of the tunnel under the 50 years operating conditions are obtained by the author with reference to a large number of tunnels in cold regions, inside and outside temperature monitoring data.2. The stress-strain relationship of permafrost tunnel has been deduced based on the theory of thermo elasticity and considering the influence of the phase change of water. After that, the coupling calculation of temperature field and strain field in permafrost tunnel has been realized by this method.3. when the surrounding rock of tunnel in permafrost region were 15% water content of sandy loam, the moisture content of 25% of the silty clay and 15% water content rate of whole weathered sandstone, the temperature field and the strain field of the tunnel are simulated by ANSYS numerical simulation software. After that, the variation law of the depth of thaw settlement with time is obtained. The 25% moisture content of silty clay is the most unfavorable frozen soil type, the tunnel vault segment is the most unfavorable position and the maximum depth of thaw settlement in the sixteenth year of operation.4. According to the permafrost tunnel in the construction and operation of two under the conditions of heat harm problems, the author puts forward the corresponding treatment measures. When the type of frozen soil is silty clay, and the water content is 25%, ANSYS numerical simulation software is used to simulate and analyze the temperature field and strain field in order to obtain the optimal thermal insulation scheme. The scheme is as follows,during the construction period, the 8cm insulation layer is laid between the primary support and the two lining. during the operation period, 2cm insulation layer as soon as possible to be laid in the surface of the two section of the lining of the thaw settlement area(arch waist, sidewall, inverted arch section). the thermal insulation performance is better than that of rigid polyurethane foam. When the program does not affect the tunnel clearance under the condition of the insulation layer, variable cross-section or unequal thickness are laid. The thickness of the roof insulation layer can be selected as a conservative 5cm. It not only achieves the goal of thermal balance and thermal insulation of permafrost, but also meets the economic and practical requirements. |
