考虑围岩传热的深埋引水隧洞TBM施工通风模拟

TBM construction ventilation simulation for deep buried headrace tunnels considering heat transfer in surrounding rock

深埋引水隧洞的储热作用及TBM施工过程中的围岩散热导致通风降温除尘十分困难。相关研究仅考虑了隧洞壁面与风流的热交换作用,而忽略了围岩内部热传导的影响;同时,目前有关围岩温度场的研究大多将岩石导热系数视为围岩导热系数,忽略了裂隙填充介质对围岩传热的影响。针对以上两方面的问题,提出基于多边形离散裂隙网络模型的围岩等效导热系数分形分析方法;进而建立综合考虑围岩内部热传导和隧洞壁面与风流的对流热交换的深埋引水隧洞TBM施工通风Euler-Lagrange两相流数学模型。结合实际工程的分析表明该工程围岩等效导热系数为0.47 W/(m·K),远低于岩石导热系数3 W/(m·K)。将本模型和传统模型的模拟结果与实测数据进行对比,验证了本模型的准确性、一致性和有效性。研究结果可为相关深埋引水隧洞TBM施工通风提供理论指导。

In TBM construction of a deep buried headrace tunnel, it is very difficult to lower the temperature and control the dust due to thermal storage effect and heat transfer in surrounding rock. Previous studies have not considered the influence of thermal conduction in the rock, and lack an analysis method for calculating its effective thermal conductivity. To address these two issues, first we develop a new analytical method for effective thermal conductivity calculations based on fractal analysis using a polygonal discrete fracture network model. Then, we construct an Euler-Lagrange two-phase flow model for the TBM construction of deep buried headrace tunnels, considering the effects of heat conduction in the surrounding rock and its heat exchange with the wind flow over its surface. Results of a case study show that the effective thermal conductivity of surrounding rock is 0.47 W/m·K, which is far less than that of normal rock. The accuracy and reliability of our model is verified by comparing the simulation results with our field experiment data and other models. This study would lay a theoretical and technical basis for similar TBM construction ventilation of deep buried headrace tunnels.