高地温隧道考虑二次衬砌水化热的隔热层厚度优化

Optimizing Thickness of Thermal Insulation Layer of High Geotemperature Tunnel Considering Hydration Heat of Secondary Lining

为揭示高地温隧道施工时二次衬砌浇筑的水化热对隔热层服役性能的影响,优化隔热层的厚度,采用数值分析方法研究高地温隧道施工期间水化热与高岩温共同下隔热层的传热规律,对比现场实测与数值模拟初期支护背后岩温变化规律验证模型合理性,并在此基础上讨论隔热层厚度与对流换热系数对二次衬砌温度场的综合影响。研究表明:1)在浇筑二次衬砌后,隔热层的主要热量传递分为3个阶段,隔热层处于两侧受热状态,即岩体中热量与水化热同时向隔热层传热、水化热由二次衬砌侧穿过隔热层流向初期支护侧、岩体中热量由初期支护侧穿过隔热层流向二次衬砌侧。2)靠近二次衬砌侧隔热层部分温度总体先上升后下降,在第2阶段内达到最大值近57℃;靠近初期支护侧隔热层部分温度总体呈上升趋势至稳定值约58℃。3)由于隔热层的存在,使得二次衬砌浇筑产生的水化热难以通过围岩来传导热量,大部分热量仅能通过与洞内空气的对流换热来散发热量。而且二次衬砌越靠近隔热层的位置其温度峰值延后出现且峰值更高。4)采用9cm的隔热层,并配合能额外提供2274.3424m3/min需风量的通风设备,能起到相对较优的降温效果。

In order to reveal the influence of the hydration heat generated by the secondary lining during high geotemperature tunnel construction on the service performance of the thermal insulation layer and further optimize the thickness of the insulation layer,the finite element numerical analysis method is used to study the heat transfer law of the insulation layer under the interaction of hydration heat and high rock temperature during the construction of the high geotemperature tunnel.The field measurement and numerical simulation is compared with the rock temperature change law behind the primary support to verify the rationality of the model.On this basis,the comprehensive influence of the thickness of the insulation layer and the convective heat transfer coefficient on the temperature field of the secondary lining is discussed.The results indicate that:(1)After pouring the secondary lining,the main heat transfer of the insulation layer is divided into three stages.The thermal insulation layer is in a heated state on both sides,i.e.the heat in the rock mass and that of hydration transfer to the insulation layer at the same time,the heat of hydration flows from the secondary lining side through the thermal insulation layer to the primary support side,and the heat in the rock mass flows from the primary support side through the thermal insulation layer to the secondary lining side.(2)The temperature of the thermal insulation layer near the secondary lining increases first and then decreases,and reaches the peak value of nearly 57℃in the second stage.The temperature of the heat insulation layer near the primary support increases to a stable value of about 58℃.(3)Due to the existence of the thermal insulation layer,it is difficult for the secondary lining to conduct hydration heat through the surrounding rock,and most of the heat can only be dissipated by convection heat transfer with the air in the tunnel.Moreover,the closer the part of the secondary lining to the thermal insulation layer,the later the temperature peak appears and the higher the peak.(4)The use of 9 cm-thick insulation layer and ventilation equipment that can provide an additional 2274.3424 m3/min required air volume and can achieve a relatively good cooling effect.