Study On Regional Seepage Field Of Natm Tunnel And Model Tests Of Catastrophe Occurance In Debris Flow Strata

In recent years, with the sustainable improvement of scientific and technology, the construction of railway traffic has been got rapid development. Adverse geological section of the water-rich fault and debris flow strata can be easily encountered in the duration of mountain tunnel passing through. This thesis is based on the national natural science foundation’Study on catastrophe behavior of working face and stability control of NATM tunnel in debris flow strata’. Based on project of the Qilian Mountains Tunnel through debris flow strata, regional seepage field and tunnel face stability test were invasitgated by means of theoretical analysis, numerical simulation and model test. The main research achivements include:1Trough tunnel engineering investigation of debris flow disaster, the Qilian Mountains tunnel environment of debris flow strata were analyzed systematic during excavation. The basis conditions and influence factors of debris flow strata occurring were clarified.2Based on the Qilian Mountains region hydro geological and engineering geological data, groundwater hydro geological conceptual model of Qilian Mountains tunnel passing through debris flow strata was modeled by using Visual—Modflow software, in order to obtain natural groundwater seepage field distribution of excavation and complement in tunnel site. Moreover, the Qilian Mountains tunnel face stability by the water-gushing was predicted. The research results can provide the theoretical reference to the tunnel face stability test in debris flow strata.3. The test device simulating debris flow occurred was developed firstly, and the impacts of debris flow occuring from head height, debris flow density, depth and material composition were studied by using orthogonal test. When depth and bulk density of single debris—flow material are constant, the higher head height the worse its stability, and when depth of single debris is constant, the lower debris-flow bulk density, the worse its stability. 4. Based on model test results, the occurring conditions of debris-flow concluding the material structure composition, groundwater and tunnel excavation section are analyzed. The debris-flow processes are divided into pregnant stage and stage of development. Pregnant stage is characterized by groundwater seepage, suffosion and piping, and collapse of debris-flow material. Stage of development is characterized by whole emission of mud and water mixture or loose debris-flow material.