Study On Sudden Water Inflow Along Galongla Tunnel In Tibet

As China's economic development, roads'construction have entered an unprecedented period of rapid development. Particularly since the introduction of the western development strategy, with the transportation infrastructure climax, the level of road construction present a unprecedented development trend. A large number of road tunnels in the high altitude, complex geologic body in the mountains will be constructed .At high altitude areas with complex geological conditions, construction tunnel is a complex technical problems compared to others. For example, the construction of the tunnels on the Bay, effective control measures to the water inrush, is urgently needed to resolve in the tunnel engineering as a major issue.In this paper, Tibet Galong La tunnel as the background, water inrush prediction and prevention system as a key point, were studied. The main contents include:1,We have surveyed the geological environment in Tunnel site, including the meteorology, hydrology, topography, stratigraphic distribution and the characteristics of the main fault structure.2,According to the distribution of surface water and groundwater data, the hydrogeological characteristics, the main contents of the hydrological geological structure, groundwater types, geological structure and the groundwater relationship,groundwater characteristics were studied.3,The theory of tunnel discharge calculation methods, the impact of the tunnel discharge were researched, based on geological data and test data.4,The theoretical results are compared with the actual water yield, combined with the actual situation of the tunnel, we have researched the Galong La fault water burst.5,Researched some drainage measures, combined with Galong La Tunnel Water, we have studied the drainage control measures applied for Galong La tunnels and new tunnels in Linzhi.Main results:1,Statistics the weather conditions for 17 months(515 days) in the tunnel site, rain and snow be often, more abundant precipitation, which have provided a continuous supply for the reserve of rock fracture water.2,The affected and restricted factors to tunnel inflow such as the topography, the lithology, the rock structure and the hydrogeological characteristics, the surface environment, the atmospheric precipitation, the tunnel length and depth were studied;At the same time,the hydrogeology units are divided according to the geological rock, the structural differences, the affecting width during the tunnel excavation and the groundwater recharge boundary conditions.3,The tunnel water inflow was calculated by using of infiltration of precipitation, groundwater runoff modulus method and dynamic method of groundwater, for Ga Longla tunnel complex geological environment and characteristics. Groundwater dynamics method result in the largest discharge between 13000 ~ 27000m3 / d, the normal discharge between 9000 ~ 21000m3 / d, which provid foundation for drawing up tunnel construction methods and support pattern.4,Compared with the actual water yield, groundwater is more close to the results, showing that, in this particular condition, groundwater dynamics method for discharge under similar geological conditions have a higher prediction accuracy, so after a similar law in the geological conditions in tunnel construction could be used.5,Tunnel seepage or leak control should be followed in"row-based, combination anti-, row, section, block;comprehensive control"principle. we should take practical and reliable measures to protect Construction and Operation safety according to tunnel geological conditions, weather conditions, the nature and development of groundwater level. Curtain grouting technology used successfully in F7 fault in the Tibet Galong La tunnel inrush treatment provided reliable technical support for the similar incidents.