Study On The Effect Of "the Chang Sha Rail Transit Line No.1" On Baisha Well

With the high-speed development of China economy and the course of urbanization, as well as the sharp increase of urban population and vehicle quantity, city transportation is becoming more and more serious. Developing urban rail transit is one of the most efficient way to solve city traffic problem. In recent years, the chinese urban rail transit is booming, many cities is or will be making effort on the construction of urban rail transport, the development of urban rail transit construction unavoidably influenced the frail urban groundwater environment. At the same time, it was provided with a long term "retardation" and "concealment", therefore it was rarely seen the research about it. People paid attention to the effect of groundwater on subway project originally, but the reverse had been the focus gradually as the enhancement of national environment protection."The Chang Sha rail transit line No.1" was a major project to promote the image of Changsha city, not only it can facilitate integral city development of Changsha, Zhuzhou and Xiangtan, but also reduce stress of surface transport in the city, impel the local economical development. But the line passed through the Baisha well, it was a argument if the construction of "The Chang Sha rail transit line No.1" will lead to the draught-up of Baisha well, or degrade water quality, decrease water volume. Based on field investigation, existing project analysis and numerical simulation analysis, this article took the analysis on the effect of constructing the Changsha rail transit line No.1 on Baisha well, provided some reference of engineering measure for protecting Baisha well. The detail and main result of researching as listed below:1.The Changsha city can be divided into four hydrogeological units based on the city areal geology environment and hydro geology environment survey, and the Baisha well which is great historical-cultural value lie in the third terrace hydrogeological unit, developed from the aggradation of Xiang Jiang ancient stream channel, the water flow of Baisha well layer was south-southeast direction. The Changsha rail transit line No.1 acted on the Baisha well was relevant to line distribution and lay depth, Cheng Nan Road station was near Baisha well, but it didn't lie in the water flow direction and lie in the second terrace hydrogeological unit, so the major research objects were Hou Jia Tang station, Nan Hu Road station and the tunnel of Cheng Nan Road station-Nan Hu Road station respectively.2.The tunnel of Cheng Nan Road station -Nan Hu Road station located in cretaceous waterproof layer below Baisha well and built by shield construction, it had slight effect on the water quality and water quantity. Hou Jia Tang station and Nan Hu Road station located in watered out direction for Baisha well, they blocked the water feeding, reduced the cross section, raised water level a little during the operating period, and they also exposed aquifer in the well, it is necessary to wreak big artificial precipitation during the construction, but the effect on groundwater will be limited into the enclosure structure due to the water stop curtain technique.3.Using three-dimensional numerical simulation software Visual Modflow to simulate excavating Hou Jia Tang station in different construction method and the influence after the station built. The results were as follows: 1) the construction of sloping opencut method will take the shape of clear descending funnel, and the area of effect was remarkable even near to Baisha well; and yet the construction method of enclosure structure setting to water stop curtain, groundwater level dropping will be specific to the enclosure structure only, surroundings were all unchangeable. Construction combined precipitation with irrigation reduced groundwater loss for the outside of recharge well, kept the groundwater level of Baisha well unchanged. 2) After the station built, the structure of the station intercepted groundwater will lead to groundwater level raising on the upstream face and lowering on the land side, but it intercepted little width, the width was similar with the station.Groundwater rising relatively small, is 0.103 meter4.To protect Baisha well, the management of Baisha well will be strict accordance with the ore resources law, it should choose the best solution for foundation ditch groundwater control of station and put great effort into monitoring water quality and water quantity of Baisha well.?...