寒区隧道衬砌冻胀力室内模型试验研究

MODEL TEST ON FROST HEAVING FORCE OF TUNNEL LINING IN COLD REGION

为了得到寒区巴郎山隧道衬砌安全性评价所需的冻胀力荷载,进行室内模型试验。将隧道板岩岩体视为裂隙介质,研究水分在裂隙中迁移产生的冻胀。模型中铺设透水布模拟裂隙,采取隧道洞腔内降温的方式模拟隧道受到的低温条件。运用热电阻元件和应变片测试试验中衬砌的温度和应变变化。试验结果表明:衬砌的冻胀应变在仰拱和仰拱脚处较小,在拱顶、拱脚和边墙处较大,最大处发生在边墙。采用数值模拟方法,分析岩石圈整体冻胀模型和含水风化层冻胀模型在衬砌上的应力分布模式,与室内模型试验结果相比较,选择含水风化层冻胀模型为巴郎山隧道冻胀荷载计算方法,即冻胀荷载可为衬砌边墙上的水平侧向荷载,冻胀力的大小可以按照洞口0.9 MPa、洞身0.6 MPa取值。

A model test was performed to investigate the distribution of frost heaving force in tunnel lining. The surrounding rock(slate) of the tunnel was considered as a fissured medium and the frost heaving force caused by water migration in fissures was mainly studied. In the model,the fissures were implemented by laying permeable fabric in the surrounding rock,and the low temperature condition was realized by putting refrigeration equipment in the tunnel. The temperature and strain changes were measured by the resistance thermometer elements and the strain gages respectively. The model test results showed that the deformation in the inverted arch and near the foot of inverted arch was smaller but the deformation in the arch,the arch spring and the side wall was larger with the largest deformation in the side wall. The numerical simulation was applied for analysing the frost heaving force calculated by different frost models. The frost model for calculating the frost heaving force produced by the water-contained weathered rock layer was selected after the comparison of the results from experiments and numerical simulation,so that,the lateral and horizontal frost heaving force acting on the side wall of the tunnel lining,0.9 MPa in entrance and 0.6 MPa in tunnel trunk was derived.