Tunnel Construction Gushing Impact And Environmental Effects On The Surrounding Groundwater System

Water invasion bursten out during the railway-tunnel construction is usually the mainly problem in constructing or operating, also which brings surface water to exhaustion and pollutes environment or effects ecology, etc.The Geleshan tunnel which crosses through Guan-yin gorge anticline which trend is near south north, is located between Tuanjie village and Jingkou village of the ShaPingBa zone, ChongQing city, which is belongs to the inducting segment of Yu-Huai railway. The Guan-yin gorge anticline appears to ridge and slot interlacing in land form, and is composed of clastic rock and carbonate rock from Jurassic Xintiangou group to Triassic. On the most top of Geleshan, there are many micromidi-reservoirs, ponds and wells built, and soluble rock exposed, which develop well and has many outlets of springs and underground rivers. Whether the Geleshan tunnel's lots of water invasion during construction period brings about surround ground water or underground water drying, threatens sixty thousands persons and two hundreds enterprises' existence, and more leads vegetation to regress, or brings about ground's collapse, etc. is the necessary problem should be considered during the tunnel construction.First, On the base of investigating Geleshan geologic environments, the author carefully analyzes them, studies their water storage structure, discusses the relationship of underground water dynamic changes and tunnel drainage by desiccation;Secondly, the author makes the dynamic analysis, regression analysis, routine hydrochemistry analysis, isotope analysis, so draws to Guan-yin gorge anticlire east and west slot's karst developing features, alternated conditions underground water and supplying drain ways;Thirdly, by stating the fissuring's surveying data, the author calculates the seeping tensor. At the last, on the base of that, the author builds up 2-D model (MODFLOW) to simulate numerical value of surrounding underground water changes by tunnel water invasion, researches the effects on surrounding underground water system for tunnel drainage by desiccation, forecasts the restoring cases after the exclusion of water, at the same, analyzes the influences in underground water level and surface collapse by tunnel excavating.