Study On Formation Mechanism, Prediction And Prevention Of The Water And Sand Inrush In Railway Tunnel Under Construction

The water and sand inrush hazard in the construction of railway tunnels is a king of geologic hazard throughout the entire development history of underground construction. In this article, 6 types of the water and sand inrush hazard happened in the construction of the national railway tunnels in recent years are referenced and analyzed in details, and the rules of their generation and development, its inner links with the surrounding rocks, geologic structure, underground water and the special geologic assembles are obtained through the analysis. It also makes a conclusion of the major control factors. The engineering geologic models that are specific to water and sand inrush hazard have been established, and the fundamental control factor for all the water and sand inrush hazards is found to be"matter-structure-force"(namely all the matters, including water and clastics, in the water and sand inrush hazard; the space for the storage of the mixture of water and sand, and the channels for inrush; the force for the water and sand inrush hazard). Based on these researchers, a new approach for the geological forecast of water and sand inrush hazard is put forward, and theoretical foundations for better prevention and control of the water and sand inrush hazard have been laid.There are three major engineering geologic factors for the control of water and sand inrush hazard:â—‹1 the material conditions for the water and sand inrush hazard; besides the detailed description of the traditional soluble rock-limestone and dolostone, researches have also been carried out on calcite cementation sandstone and mudstone. It is pointed out specifically that developed karst structure has formed in the underlying soluble rocks in the coal-measure formation, and the development rate and strength of the karst are much larger than that of the general underground water regions without coal-measure formation. The main inrush matters for the water and sand inrush hazard are divided into exogenetic matters and in-situ matters.â‘¡the research on the structural conditions for the water and sand inrush hazard emphasizes on the three foremost geological structures; folded structure, fracture structure and the relations between the primary structural plane and the water and sand inrush hazard. It is pointed out that the geologic structure developed in advance determines the principles of the generation, development and occurrence of the water and sand inrush hazard.â‘¢"two aspects and five vital functions"of the underground water in the water and sand inrush hazard were raised, making the water and sand inrush hazard be disguised, sudden and extremely destructive.Through detailed analysis and research of the common cases of water and sand inrush hazards in the surrounding rocks of the major railway tunnels, the engineering geologic models for six common water and sand inrush hazards in the surrounding rocks of the major railway tunnels have been established. On this basis, the"three principles"for comprehensive treatment have been proposed. This requires that we should make clear of the major control factors for the water and sand inrush hazard in the construction of railway tunnels, establish engineering geologic models with all the most advanced geologic forecast measures, including equipments of TSP geologic forecast equipment, SIR geological radar, Infrared Water Detector, horizontal drill and so on, to make lead geologic forecast on the basis of the traditional geologic works in tunnels, and provide theoretical foundations for the management of further construction. Then appropriate management measures should be carried out according to the practical situations in site. That is the optimum approach in case of water and sand inrush hazard in the construction of railway tunnels.