高原富水冰碛隧道洞内坍塌成因与处置技术研究——以拉林铁路米林隧道为例

Causes and Countermeasures for Collapse in a Water-Rich Moraine Tunnel in a Plateau Area:a Case Study on Milin Tunnel of Lhasa-Nyingchi Railway

为了解高原富水冰碛地层的工程地质特性,剖析其隧道洞内坍塌的成因,探索其工程处治措施,以拉林铁路米林隧道为例,对上述3个方面进行深入研究,并提出施工注意事项。研究结果表明:1)高原富水冰碛地层透水性较好,低温易冻胀,抗剪强度随围岩含石量和密实度的增加而增大,随围岩细颗粒含量和含水率的增加而减小,地表水、地下水对冰碛地层围岩有较强的浸泡软化和迁移破坏作用;2)冰碛地层中细颗粒含量较高和地下水较为发育等因素相互作用导致围岩失稳,通常是造成富水冰碛地层隧道坍塌的原因;3)对于富水冰碛地层隧道坍塌处治,主要应做好回填碴体和围岩架空区注浆加固,设置安全护拱与塌腔排水系统,并采用合理的开挖和支护方式。

The engineering geological characteristics of the water-rich moraine Milin tunnel on Lhasa-Nyingchi railway,causes of collapse,and corresponding countermeasures are studied in detail.The research results show the following.(1)The water-rich moraine stratum in the plateau is characterized by good water permeability and is prone to frost heaving at low temperatures.The shear strength increases with the increasing rock content and density of surrounding rocks,and decreases with the increasing fine particle content and water content of surrounding rocks.The surface water and groundwater have strong effects on the immersion,softening,migration,and destruction of surrounding rocks.(2)The interaction between the high content of fine particles in the moraine stratum and the development of groundwater would cause an instability in the surrounding rock,and further cause the tunnel to collapse.(3)Grouting reinforcement should be strengthened in the area of backfilling of the ballast body and surrounding rock overhead,a safety arch protection and cave-in drainage system should be set up,and rational excavation and support methods should be adopted.