The Applied Research Of The Comprehensive Physical Methods In The Advance Forecasting Of Karst During Tunnel Construction

With the improvement of people's safety consciousness, safety problem is the most important thing when the geological advanced prediction is doing. At present,almost all of the tunnel put to use advanced geological prediction, and the application of integrated geophysical methods are the most widely used.Tunnel Karst is always a difficult problem in the field of tunnel engineering.The tunnel engineering has always been troubled by the karst issue. In recent years, with the development and construction in western China, a large number of road tunnels and railway tunnels have been building in extensive karst regions, the construction problems have been complex increasingly, how to improve the accuracy of karst geological prediction has become an issue which should be solved urgently. This paper use theoretical analysis and field testing methods, combined with support projects and study of tunnel comprehensive geological prediction in karst region, to improve the accuracy of geological prediction in karst region. The specific research of this paper is about:(1)Combined with the characteristics of tunnel karst and the research status at home and abroad, the characteristics of various methods of tunnel geological prediction are analyzed. This paper describes the advantages of the comprehensive forecasting method which consists of TSP method and the ground penetrating radar method. Through the analysis of the limitation of the single exploration method, the ground penetrating radar method and TSP method can complement each other confirms advantages of comprehensive geophysical prospecting technology in eliminating the multiple solutions of the single method are explained. According to the hazards and causes of karst geological hazards in tunnel, the analysis on the basis of comprehensive advanced prediction method for tunnel karst exploration shows that ground penetrating radar method and TSP method can confirm each other and play their respective characteristics, so that the accuracy of prediction is ensured.(2)Discussed the working principle of the GPR method, observation methods and data interpretation methods, by using Gpr Max software, the forward modeling is carried out for the exploration of the karst area of the tunnel,and the rationality and feasibility are judged. The forward modelings mainly include karst water hole andkarst cavity and the karst cave at the front edge of the tunnel face, so as to make up the shortcomings of the limited radar data in the tunnel karst.Combined with typical karst images, the paper summarized and improved the ground penetrating radar method in the tunnel karst exploration of the criteria, so as to assist the technical personnel to identify the different forms and characteristics of karst.(3)The working principle, observation system, data interpretation method of TSP geological advanced prediction method as well as the TSP reflection horizon and the physical mechanical parameters of typical tunnel karst studied. Use the results of the image of the TSP system to summarize the geological prediction of the interpretation of signs.(4)Analysis on the application of ground penetrating radar and TSP integrated geophysical prospecting technique to the prediction of karst in different tunnels. The engineering example shows that the using method of the TSP and GPR, a model of comprehensive prediction of exploration, combined with preliminary engineering geological data, we can specify the accurate location and reliable characteristics of tunnel karst, the prediction results can meet the requirements of the safety of karst tunnels construction.As karst tunnel prediction methods, TSP method and ground penetrating radar synthetic method,which used in the prediction of shapes and positions of tunnel karst, show the high The efficiency and accuracy of the combination of the length and the length of the tunnel karst exploration.