The Study Of Early-Warning On The Construction Hazards In Karst Tunnels

Under the circumstances of today’s society, the construction of tunnels has been very common, and the amount of tunnels through karst areas is also getting more and more. However, water burst inrush, rock burst and gas are so common under the construction of tunnels in karst areas that the equipment is usually damaged delaying the schedule, or more seriously resulting in the casualties. So, the study of early-warning on the construction of hazards in karst tunnels has been a great problem that needs to be solved as quickly as possible.For one thing, dolomitic limestone and limestone are widespread in the area where Xulingguan Tunnel, Naqian Highway goes through; and the location of the tunnel is in the seasonal variation belts where crevasses, fissures and karst conduits are highly developed; For the other thing, there are three underground rives named respectively Zhan Di, Wayaogou and Old Snake Cave, and all of these rivers mentioned above has been flowin from south to the north. Thus, in order to ensure the safety of the construction and operation, geology, fuzzy mathematics, advanced forcast methods and numerical simulation are combined to study the early-warning system.In this paper, the basic karst development rules were analyzed based on studying the literatures and doing research. The main controlling factors of karst development, which are affected by stratum lithology, geological structure, underground water hydrodynamic zoning, landform and etc., were mentioned. The hierarchical structure for the index of risk assessment for karst is built through the analysis of main controlling factors for karst. And four-level risk ranking standards are put forward on the basis of risk evaluation model from fuzzy mathematics, thus accieving the qulification of risk evaluation for kasrt tunnel; the particular location of karst behind tunnel face is revealed by the advanced geological forcast, which brings great convenience to the construction; dynamic early-warning for construction is also achieved by the method of numerical simulation, which is of great significance to the guidance for site operation.