Study On Mechanism Of Inrush Water Geological Hazards And Warning Technology Of Karst Tunnel

All kinds of geological hazards, particularly inrush water geology hazard which is the greatest hazards of all geological hazards, will occur when Karst tunnels go through complex special geology, geomorphology and tectonic units. Mechanism of inrush water geological hazards and warning technology of karst tunnel have been studied in this thesis, including causing, mechanism, theoretical analysis, forecasting method, warning method and standard and in-situ application. Conclusions are as follows.1. The formation and occurrence of water geology hazard must have four basic conditions which is separately that special geology structure, enough filling substances, abundant underground water and artificial excavation disturbance activation by analyzing mechanism and characteristics of inrush water of domestic and oversea karst tunnel.2. Automated network monitoring system of inrush water geology hazard of tunnel was seldom studied at home and abroad. The accepted widely applicable processing model of monitoring data has always been not presented at present, particularly warning and forecasting of inrush water geology hazard of karst tunnel which has no mature precedents. Therefore, it is of great importance to safety construction of tunnel to develop warning system.3. Thin plate theory and shear failure theory are used to study mechanism and characteristics of inrush water. The plate theory is suitable for large span tunnel with thin and well integrity water-resisting rock plate. On the opposite, the shear failure theory is suitable for small span tunnel with thick and broken water-resisting rock plate. Finite element method is used to simulate the changes of water-resisting rock plate mechanism while tunnel excavation closes to pressurized caverns in the 3D state. The results indicate that water-resisting rock plate begins to become relaxed and cause hazards easily.4. Disaster precursory phenomena prediction method and S-t curve tendency changes judge method is firstly presented on the basis of the prediction method of inrush water geology hazard of karst tunnel. The key of the method is to real-time monitor to activity patterns of underwater and stability of rock mass, including water pressure, water quality, around rock displacement, steel arch stress, etc.5. The basic evaluation factor of inrush water geology hazard of karst tunnel include tectonic features, water inflow features, rock stability characteristics, ground surface environmental features and harmful levels of disaster. It is of great importance to make disaster emergency plan that inrush water geology hazard is divided into four grades according to the above evaluation factor.6. The comprehensive qualification evaluation factors and the evaluation indexes of poor geology structures of karst tunnel was studied, included faults index and weight factors, karst index and weight factors, recalculating region index and weight factors that underground water goes through and water resource recharge characteristics index and weight factors. The qualification indexes T was determined by comprehensive qualification evaluation. Then harmful levels of disaster were divided into four grades according to value of T. The monitoring items are determined for each grade and the disaster emergency plan is made when tunnel excavation goes by the ground.7. The main risk resources of karst tunnel were monitored which was separately that water pressure, water flow, water quality, the internal force of preliminary support and the displacement of rock mass. And the relative standard values were made. The warning system of inrush water geological hazard of karst tunnel has developed on the base. The results of in-situ experiment in Liuyanghe tunnel of Wuhan-Guangzhou railway and Dazhiping Tunnel of Yichang-Wanzhou railway indicate that the warning system is quite stable and is able to adapt to complex environment, popularization and application of which has some guiding significance to construction safety of karst tunnel. It is instructive greatly to the application of the warning.