Study on the Evolution Process of Negative Effect of Groundwater Environment Induced by TBM Tunnel Construction
When TBM tunnel passes through slightly weathered tuff,joint dense zone and fault fracture zone,it is easy to induce water gushing in the tunnel,resulting in groundwater level drop,water resources loss,surface collapse and so on.This paper is based on the joint drainage design of drainage holes+deep holes to study a new type of joint drainage segment suitable for high water pressure environments.In view of the above,based on the equivalent lining method,the finite element software system is used to analyze the evolution characteristics of pore water pressure,water inflow from excavation surface and groundwater level under advanced grouting and without grouting during the process of TBM tunnel excavation.The data analysis software is used to fit the relationship between the total water inflow of the tunnel and the lowering depth of the groundwater level.The results show that the pore pressure ratio caused by advance grouting in the tunnel decreases with the increase of the permeability coefficient of geological strata,and the influence height and width of seepage field are effectively controlled.Advance grouting makes the pore pressure ratio of the vault on the excavation surface of the tunnel basically keep at the same horizontal line during construction,effectively reducing the rising rate of total water inflow.The groundwater level drop depth increases with the increase of tunnel driving distance,and there is a linear positive correlation between groundwater level drop depth and tunneling distance.The research results can provide technical support for the treatment of the negative effects of groundwater environment induced by the actual construction of TBM tunnel through poor strata.
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