Research On The Engineering Properties And Tunnelling Construction Technologies Of Poorly Cemented Sandstone Aquifer

The aquifer of poorly cemented sandstone is similar to the common water-rich sand and silty sand layer in the subway engineering, However, in the mountain conditions, due to its unique engineering properties, the cohesion of surrounding rock is low and stability of surrounding rock is poor, also with greater depth of mountain tunnel, the rock disturbance caused by the tunnel excavation and soaking of the surrounding rock in water, finally causing rock collapse, liquefaction, serious deformation of tunnel support and even tunnel collapsed.In this paper, we analyze the surrounding rock characteristic and tunnel construction technology features of poorly cemented sandstone aquifer combined with Tao Shu Ping tunnle and Hu Ma Ling tunnel which are parts of the Lan-Yu Railway, the main work and the conclusion of research are as follows:Firstly, the concrete work conclude sampling of undisturbed soil in Tao Shu Ping tunnle and Hu Ma Ling tunnel and laboratory investigation of the soil, after derive the physical and mechanical properties of poorly cemented sandstone aquifer and combine with previous research results for the sandstone, we analyze and summarizes the water engineering properties of poorly cemented sandstone aquifer and also derive the physical and mechanical parameters and time-related features of the poorly cemented sandstone aquifer through experimental design and research.Secondly, aimed at the engineering condition, we determine the appropriate excavation method according to the numerical simulation results combined with the construction process and the degree of difficulty of the construction, and deeply analyze the issue of the application time of secondary support in CRD construction method.Lastly, after a long time of the tunnel construction in the poorly cemented sandstone aquifer, construction units also have a relatively clear understanding of the poorly cemented sandstone aquifer, basing on various response measures used in the investigate construction, Based on the summary of experiences and lessons,this paper present the key techniques of construction method on the weak cemented sandstone aquifer to provide a reference for the subsequent tunnel and tunnels in similar stratum.