Based On The Fractal Characteristics Of Karst Landform Elements,the Water Inflow Prediction Of The Tunnel In The Western Hubei Section Of Zhengzhou-wanzhou Railway

The total length of zhengzhou-wanzhou railway is 748.084km,which is not only the main rapid passenger transport channel between southwest China and central China,north China and northeast China,but also an important part of the rapid passenger transport network in southwest China and the"four vertical and four horizontal"passenger dedicated line network of China's railway.The terrain and geological conditions along zheng-wan line are complex and the project is arduous.Water gushing during tunnel construction in the complex karst area of shennongjia fornix is a problem that must be solved.The study of tunnel water inrush in karst areas must pay attention to the study of karst development rules and karst morphology distribution characteristics,but the hydrogeological conditions in karst areas are always complex,karst morphology and scale is difficult to accurately detect.The fractal theory is a powerful tool to study the"irregular"law of karst development.The quantitative study of karst geomorphology is of great theoretical significance to the quantification of karst morphological distribution characteristics.Author based on the fractal characteristics of karst landform elements,the statistics and analysis on the factors of karst landform,the fractal methods to characterization of karst landform,establish karst landform elements corresponding relation with the condition of the underground karst development,and the development degree of karst landform influence catchment condition and infiltration intensity perspective,according to landform fractal feature selection calculation parameters of tunnel water inflow and explore a new method of tunnel water inflow parameters selection,and western hubei section of zheng wan railway tunnel water inflow forecast.Based on the understanding of regional geological background and karst hydrogeological conditions,this paper makes statistical analysis of karst landform elements in the study area by combining conventional statistics and fractal theory,reveals the spatial distribution law of karst landform elements in the study area,and divides the fractal dimension value range of karst landform elements.At last,the water inrush problem of each tunnel section through the soluble rock stratum is predicted.The main research results are as follows:1)by comparing the lithology,exhumation,water content and karst development degree of the soluble rock strata in the study area,we can generalize the upper Cambrian loushanguan formation??₃O₁l?,qinjiamiao formation??₂q?and sinian upper dengying formation?Z₂?₁dn?into the soluble rock with high karst development degree.The lower ordovician?O₁n^g?,lower Cambrian shilongdong formation??₁sl?and lower Cambrian tianheban formation??₁t?were generalized into the soluble rocks with moderate karst development.Middle and upper ordovician(O₂₊₃b),lower Cambrian shipaig formation??₁s?,lower Cambrian niutiutang formation??₁n?,and shencaohe formation?Pt₂s?are summarized as water-bearing rock formations with low karst development.2)according to the division basis of karst water system,the karst water system is divided into eight karst water systems.3)through routine statistical analysis of geomorphic elements in the study area,the following laws are found:the overall trend of mountains in the study area?ne-sw?is parallel to the regional grand tectonic xinhua fault,which is close to the core of the fornix.The denser the mountain distribution is,the higher the peak elevation will be.The river length in the study area is generally<10km and mainly develops at the elevation of 400-1000m.There are 147 depressions in the soluble rock strata in the study area,of which 81.6%are less than 0.1km2.The number of depressions in the study area is controlled by the lithology of the soluble rock stratum.4)using the fractal method to calculate the peak body morphology in the study area,it is concluded that the karst landform development belongs to the period of young^mature,and has the power to continue to expand and develop in depth;Through the fractal calculation of the rivers in the study area,it is found that the fractal dimension of rivers is negatively correlated with the degree of karst development.According to the statistical analysis of the fractal dimension values of149 depressions in the study area,it is found that the mountain planation plane and the huiyuan planation plane,which are developed at the elevation of 1300-1500m,are the concentrated areas of the depressions.The topographic lines in the study area were divided into blocks with kilometer grid,and the fractal dimension values of each topographic lines in the"kilometer grid"were calculated with the two-dimensional mesh coverage method.According to the borehole data collected in the study area,it is confirmed that the fractal dimension value of the topographic line in the study area is divided into five ranges?<1,1¹.2,1.2¹.5,1.5¹.8>1.8?,corresponding to weak karst development,weak karst development,medium karst development,strong karst development and strong karst development,respectively.5)from the perspective that the development degree of karst geomorphology affects the catchment conditions and the infiltration intensity,the fractal characteristics of geomorphologic elements of railway tunnel crossing different regions are fitted to predict the inrush water volume of each tunnel section.In the process of calculating the water inflow,according to the fractal dimension value of topographic lines in the cell grid,the infiltration coefficient of atmospheric precipitation is selected by the"range boundary value method".It is predicted that the normal water inflow of chufeng tunnel can reach 43483.7 m³/d.It is predicted that the normal water inflow of xinhua tunnel is 30983 m³/d.It is predicted that the normal water inflow of ganjiashan tunnel and xingshan tunnel is 11365.58m³/d and10433.67m³/d respectively.