溶岩与非溶岩地区隧道排水系统堵塞机理

Blockage Mechanism of Tunnel Drainage System in Karst and Non-karst Areas

岩溶与非岩溶地区隧道排水系统频繁发生堵塞灾害。溶岩地区排水系统堵塞物质主要为白色碳酸钙(CaCO_(3)),而非溶岩地区排水系统堵塞物质为黑色土颗粒。以法国Meyssiez隧道排水系统堵塞灾害为依托,通过测试隧道围岩孔隙比e和地下水电导率EC,分析了岩溶地区隧道排水系统的堵塞机理。试验结果表明:(1)溶岩地区排水系统堵塞主要由以下过程引起:(1)雨水入渗地下后,溶解了围岩内部的碳酸钙,形成Ca^(2+)和HCO_(3)^(-)离子;(2)含有Ca^(2+)和HCO_(3)^(-)离子的地下水通过排水孔流入隧道内部的排水系统。由于气温和气压等外部因素改变,Ca^(2+)和HCO_(3)^(-)离子反向沉积形成固态CaCO_(3)结晶,最终引发排水系统堵塞;(2)非溶岩地区隧道排水系统堵塞灾害由以下过程引起:(1)地下水流作用引发围岩内部细小土颗粒迁移流失;(2)流失的细小土颗粒通过排水孔进入隧道内部排水系统,而后逐步堆积,最终引发排水系统堵塞。

Tunnel drainage systems in karst and non-karst areas are frequently blocked.The plugging material of the drainage system in the karst area is mainly white calcium carbonate(CaCO_(3)),while that in the non-karst area are black soil particles.Based on the engineering disaster of drainage system blockage in the Meyssiez Tunnel in France,this paper analyzed the blocking mechanism of tunnel drainage system in karst areas by testing the void ratio of surrounding rock and the electrical conductivity groundwater.The test results indicate that:(1)the blockage of the drainage system in the karst area is mainly caused by two processes:①after rainwater infiltrates underground,calcium carbonate inside the surrounding rock is dissolved to form Ca^(2+)and HCO_(3)^(-)ions;②groundwater containing Ca^(2+)and HCO_(3)^(-)ions flows into the drainage system inside the tunnel through drainage holes.Due to the change of external factors such as air temperature and pressure,Ca^(2+)and HCO_(3)^(-)ions are reversely deposited to form solid CaCO_(3)crystals,which eventually cause blockage of the drainage system.(2)The blocking disaster of the tunnel drainage system in non-karst areas is caused by the following processes:①migration and loss of fine soil particles inside surrounding rocks due to groundwater flow;②the lost fine soil particles enter the internal drainage system of the tunnel through drainage holes,then gradually accumulate,and finally cause the blockage of the drainage system.