Study On Tunneling Technology Of Large-diameter Shield Tunneling Through Yellow River Silty-fine Sand Strata

River system has well developed in our country.With continuously developing of urbanization,the engineering of applying the mud-water balance shield to the construction of river crossing tunnels in saturated clay soil is becoming more and more mature.However,it crosses the Yangtze River in a long distance in the fine sandy soil layer that is hydraulically connected to the river.The Yellow River has fewer cases,and key problems in construction need to be resolved and further improved.After reading a large amount of literature and data,this paper carried out a research on crossing the Yellow River for the intelligent heating project of YinChuan city with the help of huadian lingwu power plant.In the course of passing the Yellow River and the Yellow River dike,the shield tunneling of this project mainly passes through the silty sand stratum with rich water content,large permeability coefficient and poor self-stability.Therefore,the tunneling and excavation of pulverized sand stratum is studied to find the safe construction method and the way to improve work efficiency.The main contents are as follows:(1)Mud-water shield construction mainly relies on the circulation of mud for construction operation,and the selection of mud materials is as many as dozens of,China is currently mainly based on bentonite.As many as dozens of,because the mud configuration is the main reason affecting the stability of this engineering excavation face,so the author needs to determine the shield in the fine sand strata dug in the process of cutting the best mud ingredients,through the field data collection and related laboratory soil test,adjust the water in the mud,bentonite,CMC,soda ash and other different mixing proportion,to ensure the stability of excavation face excavation process.(2)Collecting statistics and data analysis of the tunneling parameters during the construction process.The analysis includes: total thrust,tunneling speed,rotary speed,rotary torque,average pressure of soil bin,etc.Arrange the tunneling parameters and settlement data,analyze the changes of each parameter and the influence of each parameter on the ground settlement deformation during the tunneling process.(3)In this paper,plaxis finite element calculation software is used to simulate the excavation process of the shield tunneling through the east and west levees of the Yellow River,calculate the simulated surface settlement of the tunnel,and compare the surface settlement measured on site to verify the correctness of the model.