Multiscale Hydrogeological Model Of Complex Karst Mountains

In southwest China, Guizhou, Guangxi, Yunnan, Sichuan and Hunan belong to the complex karst mountain area which the stratigraphic distribution of soluble carbonate rock is extensive and karst hydrogeological conditions are extremely complex.With the rapid development of the construction in southwest China, the problem of the complex karst hydrogeology and construction projects of mutual influence have been increasingly concerned.Numerical simulation is the main method to research this problem,but it still has some shortcomings:There is a contradiction between the boundary conditions of uncertainty and simulation accuracy karst water system, and a complex difficult karst media generalization. In view of this, based on multiscale simulation of hierarchical patch dynamics paradigm (HPDP), this paper propose that using the software of MODFLOW establishes multi-scale hydrogeological model under the complex mountainous karst hydrogeological conditions, and taking an example predicting the effect of construction of one part of the water diversion projects, named XiaoPu tunnel in Yunnan is to verify this model, proposing the method for the establishment of a high precision complex karst mountain groundwater model has an important guiding significance.According to the case and the hydrogeological conditions of XiaoPu tunnel under complex karst mountain, we has established a method of complex multi-scale karst mountainous space hydrogeological model for medium-scale model of each generalization, and hydrogeologic parameters and boundary conditions have been researched and described.And on the basis of karst hydrogeological conditions XiaoPu tunnel-depth study, in the study area,available models have been establishedin XiaoPu space karst area under multi-scale hydrogeological conditions. The main results and conclusions are as follows:(1) In the complicated karst mountainous multi-scale and hydrogeological area, models is generally composed of a large scale model and a plurality of sub scale models.The main area of the large-scale model is to evaluate the overall regional groundwater resources, determine the boundaries of the model secondary scales; secondary sub-scale model is mainly to evaluate groundwater dynamic characteristics in key areas, and quantitate evolutionary trends accurately of prediction.(2) Large-scale models of porous media uses the equivalent of karst medium river, dissolved pores, dissolved gap.The gap is dissolved fracture and matrix generalization; sub-scale model of the river pipeline will need to have a role in controlling water use in MODFLOW streams sub-module (STR) separate generalized. Infiltration model coefficients determined by the water balance method, permeability, water level, is to generate porosity through experiments and empirical data acquisition and inversion through PEST module. Large-scale model of the boundary must expand beyond the fixed boundaries to make sure the secondary boundary determined by the initial scale models predict large-scale model results.(3)The study area of XiaoPu tunnel of Water diversion project in yunnan is typical complex karst mountainous area,located in the surface watershed area of the Yangtze river and pearl river valley,the development of geomorphic types such as Erosion, corrosion accumulation is complete.Sets of karst stratumin Permian-before sinian is developed in the area,karst of the area is typical and diverse.Karst water of the are aaccept atmospheric rainfall,controlled by topography, lithology and structure factors,through dissolution gap run off and excretion.In addition to the controlled by lithology, tectonic development zone also enrichment for karst water.Wang Jawan fault in the area, The stone river-ChangLingGang fault and Anhua syncline strongly controlled the enrichment and movement of karst water.(4)Groundwater runoff of the karst groundwater units are roughly tallying with the actual situation in multiscale hydrogeological model of XiaoPu tunnel.According to the preliminary prediction of large model,determine the two key affected area of south, north of the tunnel blocks use subprime scale models.The north of Xiaopu tunnel on subprime scale model simulation results show that:Karst segment without blocking the water level drawdown under the condition of maximum of160m, scope as far as can be up to15km, the maximum block off of Karst segment in one unit length of period of rainy season is13.8m3/d m;Although under construction conditions of block off influence scope did not decrease significantly,but influence greatly weakened,the deep of underground water level is generally only10-20m,the maximum block off of Karst segment in one unit length of period of rainy season is1.62m3/d·m.The south of Xiaopu tunnel on subprime scale model simulation results show that:Tunnel of karst segmen within karst groundwater runoff area,have less effect on the downstream discharge area of karst groundwater level,the water leve of upstream recharge area is reduced in a certain degree.Without blocking the maximum block off of Karst segment in one unit length of period of rainy season is4.28m3/d·m, block construction condition dropped to0.63m3/d·m.Through successfully in the study area of Xiaopu tunnel modeling practice of the water diversion project in Yunnan, verify the feasibility and rationality of multiscale hydrogeological model of complex karst mountains.This kind of modeling method provide a reference for the future study of the theory and practice.