Mechanism and key controlling technology of water inrush in tunnel construction

摘要

With the rapid development of underground construction, it is the largest number of karst tunnels that is being built in China, even the scales and the difficulties for tunnel construction. The hydrogeological conditions are becoming unprecedentedly complex, and the geological hazards are becoming severer, such as water inrush and mud gushing. So it is imperative to reveal the mechanism of water inrush and improve the key technology of hazard prevention and treatment. In this paper, we will provide a brief background on the water inrush cases of traffic tunnels and hydraulic tunnels. The occurrence conditions of water inrush are briefly introduced, this will be followed by a description of energy storage of water structure, dynamic performance of karst water, energy liberation and the failure of water-bearing structure, and influence factors of water inrush have been classified as karst hydrogeological factors and engineering disturbance of human factors. In terms of the formation of water inrush channel, water inrush types are divided into geological defects inrush, non-geological defects inrush and the combination, mechanical models and criterions of water inrush for each type have been established, such as water inrush of fractured rock induced by high-hydraulic fracturing, water inrush of filling fault and karst conduit caused by hydrologic barrier instability. Based on the statistical analysis of influence factors for water inrush in karst tunnels, the relative weights of geological defects, underground water level, formation lithology, landform, attitude of rocks, excavation and reinforcement, geology prediction and monitoring and measurement have been obtained according to the means of frequency statistics, and a fuzzyAHPmodel for risk ofwater inrushwhich can improve the accuracy of risk assessment is established by the comprehensive weight combination method. Based on the risk assessment of water inrush during tunnel construction, an optimal system for water-bearing structure detecting in which prediction methods vary with the risk level of water inrush is probed. According to the characteristics of treatment of typical water inrush, we put forward the hydrodynamic treatment principle, an anti-dispersed and gelatin-controlled hydrodynamic grouting material and matching technology has been developed, and the treatment system of water inrush is established.As a result, the hazard prevention&treatment technological system of water inrush in karst tunnel is composed of risk evaluation system for water inrush, comprehensive geology prediction system and treatment technological system. It has been successfully used for hazards prevention and treatment for water inrush of Qiyueshan Tunnel in Hurong highway, including risk assessment, hazard source detection and treatment of water inrush. The system can be widely applied in hazards prevention and treatment for underground engineering. It can be used for risk assessment, prediction defection and grouting treatment where water-bearing fractures are well-developed in the rock mass.