| With the rapid growth of world population and economy and climate change,uneven distribution of regional water resources and the shortage of water resources has become one of the urgent problems in economic and social development,the construction of cross river or across the area of water diversion project has become an effective way to solve this problem.Karst area in southwest China,diversion tunnel as a linear structure occurs in underground geological body,in the process of the excavation,will reveal all sorts of formation and destruction water or water potential of surrounding rock,the change of groundwater flow field,make the surface well,spring,the phenomenon of the dry.Tunnel after excavation,ground water continuously into the tunnel,the perturbation range of groundwater seepage flow direction,the permeability of rock mass,surface water and groundwater runoff will be a certain degree of change,therefore,evaluate and predict the effects of tunnel construction on groundwater environment level has become the indispensable important procedure before major construction projects.Paper based on phase superposition associated black home city region caused by seepage field evolution,in the thorough investigation,the study area geological environment condition,karst hydrogeology condition,on the basis of the "introducing Er into bing" project(1987),"north main canal" project(2006),water diversion project in yunnan associated tunnel black home city section(2018)mainly engineering disturbed has carried on the qualitative analysis;Use of abundant field investigation and survey data,the system studied black city spatial structure of aquifer and boundary conditions,on the basis of 289 long borehole pressure water test set parameter selection,the 3 d seepage numerical model was established,using the Modflow software inversion,and forecasts the water diversion engineering tunnel construction at various stages of the impact of groundwater environment,get the main conclusions are as follows:(1)Iinversion of the groundwater flow field under the original condition.1987 years ago,the study area is not any project construction of the original state,major is given priority to with the horse mountain-wellknown granny karst water system,the qingshan formation water and karst development is higher,after the supply by atmospheric precipitation,the karst depressions,funnel,sink,rivers into the karst piping systems,such as migration along the fracture zone,main direction and on the east side to the west side of erhai lake river discharge,including black city artesian well water level(2050 m),the woman of wellknown reservoir water level(2080)were the main discharge point in the study area.The groundwater level in the study area is generally north high-south and low,and its water level is between 2280 ~ 1980 m,under the control of the terrain,water rock group distribution and structural development.In the original state,the groundwater level in the engineering area of "the guide to the pearl" project is between 2000 and 2100 m.The groundwater level in the engineering area of "north trunk canal" is between 2000 and 2050 m.(2)Inversion of the influence of the project implementation on the seepage field of groundwater.After 1987,"introducing Er into bing" project tunnel to about 1945 m elevation through the water and karst development is higher qingshan formation,caused by tunnel captured of groundwater,became the south minimum discharge datum in the study area.Overall groundwater level in the study area between 2280 ~ 1940 m,is located in the fault zone can be lava with the lava place woman of wellknown reservoir water levels from 2080 m to 1980 m,lead to the dried up,the biggest impact range is 3000 m,the lowest groundwater level dropped to about 1950 m,because of the lotus song set of relative water-resisting layer barrier,city north of the black family confined artesian well wellhead or supply area are located outside the scope of tunnel effect,is not "lead Er into bing" affect tunnel construction projects.(3)The effect of "north trunk canal" project on seepage field of groundwater.After 2006 as "the north main canal" project of groundwater seepage field,the project from "introducing Er into bing" outlet,to about 1930 m elevation through water weak and weak water permeability basalt,group,and "introducing Er into bing" engineering tunnel as the study area south minimum discharge datum.Overall water level in the study area between 2280 ~ 1940 m,and the engineering tunnel biggest influence range is 1000 m,down to about 1950 m of the groundwater table,the west village pond near the tunnel from 1890 m to 1870 m,lead to the dry up.(4)To predict the effect of drainage on the seepage field in the construction of the black home of the haidong tunnel in the central yunnan province.After 2018,associated tunnel diversion project in yunnan black home towns paragraphs to the northwest-southeast to cutting the horsehead mountain-wellknown granny karst water system,the construction of the tunnel will be the new drainage datum,and groundwater in south area continue the original drainage datum "introducing Er into bing" tunnel,tunnel discharge "north main canal".The impact radius of the project is about 500-1100 m,and the lowest groundwater level is about 2000 m.Among them,the maximum impact range of 3# hole construction is 300 m,and the lowest water level of groundwater is reduced to about 2000 m.The maximum impact range of the construction of 4# hole construction is 300 m,and the lowest groundwater level is reduced to about 2000 m.Due to the development of karst formation in the qingshan formation(D1q)formation in matou mountain,the underground water level of the hole outlet is close to the bottom of the tunnel,so there is no obvious change in the surrounding groundwater level.Due to the blocking effect of the lotus group's relative isolation layer,there is no tendency of attenuation and decrease of flow rate in the self-flow well of the black home,which is 3.8 km away from the northeast,and the project implementation has no effect on it.(5)To predict the recovery of seepage field under the condition of complete closure of the black family of the haidong tunnel in the central yunnan province.After 2026,the seepage field was restored under the condition of complete closure of the black family and city section of the haidong tunnel,the water diversion project in the central yunnan province.The water level of the tunnel entrance was about 50 ~ 150 m after the project was blocked for 1 year.The seepage field of the entrance section of the tunnel for three years was quickly restored,and the area was basically restored to 80% of the current state.After five years,the seepage field was basically restored to the status quo after the implementation of the "north canal" project. |
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