Study On Mechanism And Control Technology Of Interaction Between Fractured Rock Mass Tunnel And Groundwater Environment

Tunnel construction and groundwater environment and derived ecological environment are mutual influences contradictions. It is technical problems to fight to groundwater to tunnel builders. On the one hand, groundwater impacts tunnel, such as water and mud inrush risk in the course of tunnel excavation, and high water pressure risk of fully wrapped waterproof, and lining leakage risk during operation stage. On the other hand, tunnel impacts groundwater, such as groundwater resources loss and water level decline and ecological environment depravation. The two mutual influences contradictions involve to construction safety and environmental protection and economic input and social effect and so on. The author intensive studies mechanism and control technology of interaction between fractured rock mass tunnel and groundwater environment. The research result can provide support of guaranteeing construction and operation safety and protecting groundwater environment.Because of variety and complicacy of groundwater and anisotropy of fractured rock mass and dynamics of tunnel construction, it is difficult of the scientific study of interaction between the two contradictions. Based on characteristic of fractured rock mass tunnel, by comprehensive methods of theoretical analysis and numerical calculation and field monitoring and engineering application, the author researches the influence rule of tunnel to groundwater environment in period of construction and operation stage, and studies the influence rule of water pressure against lining of groundwater environment to tunnel in period of operation stage. It is proposed technical evaluation system of interaction between fractured rock mass tunnel and groundwater environment. The research results are applied to Shibanshan tunnel of Shijiazhuang-Taiyuan passenger railway and Dongkeling tunnel of Guiyang-Guangzhou railway. The research results include the following.(1) The research stages are divided into initial stage and construction stage and operation stage. The influence factors are divided into uncontrollable factor and controllable factor. The research emphasis and objects of each stage are proposed.(2) Based on seepage characteristics of fractured rock mass tunnel and characteristics of construction stage and operation stage, considering stratification and occurrence of fractured rock mass, the equivalence seepage model is building of heterogeneous and anisotropism of fractured rock mass tunnel. The model can simulate influence of excavation progress and structure construction progress and different waterproof and drainage measures.(3) The author researches groundwater permeability rules in periods of construction stage and operation stage, and analysis the change rules of seepage velocity and water table and water loss amount and drainage influence radius in periods of construction and operation stages.(4) The author reveals the interaction mechanism between fractured rock mass tunnel and groundwater environment. The research results include the influence rules of uncontrollable factors and controllable factors to groundwater loss amount and water level change and water recovery and water pressure against lining.(5) The author suggests engineering measures during the runnel site selection and design and construction and operation stage, in order to protect groundwater environment and decrease water pressure against lining. These suggestions include that tunnel site should be selected at low permeability horizontal stratum, and high altitude tunnel can decrease water table buried depth, and every step closed construction methods, such as CRD method and both side drift method and CD excavation method, can decrease groundwater environmental damage, and decrease closed time and increase shotcrete anti-penetrability performance and reduce shotcrete and lining leakage and ensure construction quality of waterproofing and drainage tube. Grouting reinforcement measure can decrease water loss amount and decrease drawdown, and also decrease water pressure against lining. Grouting reinforcement measure is effective to realize limited drainage as well.(6) The author proposes evaluation technical system of interaction between fractured rock mass tunnel and groundwater environment. The evaluation technical system includes four evaluation targets (Ui). The evaluation index system includes five groups and twenty nine evaluation indexes. The evaluation method is phased evaluation method of prediction(Upi) and control (Uci) of negative effect evaluation. Accordingly, it is established of the five evaluation grades standard using hundred-mark system. Finally the evaluation method of limited drainage necessity is proposed which include Ⅰ～Ⅳ four grades. Each necessity grade has respective engineering measures.(7) The results are applied to Shibanshan tunnel of Shijiazhuang-Taiyuan passenger railway and Dongkeling tunnel of Guiyang-Guangzhou railway. Based on different tunnel environment features, the author forecasts and evaluates negative effect grade of interaction between tunnel and groundwater environment by above evaluation method. Based on discriminating of limited drainage necessity grade, corresponding engineering measures are adopted in above tunnels to protect groundwater environment and improve groundwater level recovery.