Statistical Analysis And Calculation Of Water Flow In Southwestern Karst Tunnel

With the continuous expansion of the construction scale of Chinese railway and highway transportation system,many underground projects that need to cross the karst area have incresasingly suffered from karst intrusion during construction,design,and operation.The southwestern karst tunnel is especially prominent for water inrush.Many experts have conducted extensive research on the prediction of water inrush from tunnels and have achieved certain achievements.At present,the theory of water balance and groundwater hydraulics have been widely used in engineering.However,in many cases,because the geological structure involved in the tunnel is too complex,with the most prominent in the southwest region,most of the theoretical calculation methods are based on groundwater equilibrium principle or Darcy's law,and are solved through the establishment of formulas.In the process of solving,due to the uncertainty of the boundary and parameters,it is often required to artificially simplify or cut down some actual geological conditions.However,sometimes due to lack of understanding,some important factors may be missed,which seriously affects the prediction effect of these algorithms.It is predicted that the amount of water inflow differs greatly from the actual amount of water inflow and often cannot meet the requirements of actual work.With the increasing number of tunnels built and tunnels under construction in the southwest,through the number of actual water inrush samples collected in the southwestern karst tunnel,and starting from various factors affecting the water inrush from the tunnel,mathematical surge methods are used to establish water inrush.The mathematical calculation model supplements the traditional method of predicting water inrush.Through the visits to the project during the post-graduate study,the data and documentation were collected.From the perspective of mathematical statistics,the case of the water inrush disaster in the karst tunnel project in Southwest China was explored.From the collected data itself,seek the internal relation between data,and used a variety of mathematical methods,such as multiple regression analysis,to address the formation of karst water inrush disasters.Factors and basic geological conditions of this research object,the construction of the corresponding mathematical calculation model.The main results of the study are as follows:(1)Based on the data collected from 128 outbreaks of water inrush from 30 completed karst tunnels in the southwestern region,the conditions for the formation of water inrush disasters in the karst tunnels in the southwestern region have been analyzed,focusing on the identification of tunnel karst surges.The main causes of water inrush and influencing factors.Combining with previous research results,the statistical analysis of the inrush water tunnels in Southwest China has been conducted.The formation mechanism of disatersof the karst water inrushhas been analyzed from five aspects including topography,formation lithology,geological structure,karst hydrodynamic belt,and climate.(2)In tunnel gushing water bursting to mathematical calculation model of mode choice,mainly based on the existing research,and through the analysis of the carding,and again in the southwest karst tunnel surge in combination with the actual data of water inrush for,select the collection tunnel flood water inrush is relatively full and accurate information in the paragraph as a calculation sample set,has led to a mathematical calculation model of comprehensive selection of eight indicators,respectively,the length of the lava,lava composition,tunnel circulation zone,rock structure,the level of surrounding rock,rock strata thickness,strata dip Angle,the slope.(3)The quantified value of the selected calculation index was established,and the calculation index system was established.The quantification principle of the risk evaluation indicator for the inrush water bursting in the karst tunnel established by Yang Yanna was used to quantify the indicator,and it was dimensionlessly treated and normalized.In addition,the missing data is filled by multiple replacement methods.The weight of each factor is determined by the AHP method to ensure the prediction results are more accurate,and the interference of the missing data to the predictionresults is eliminated.(4)Through the collection and analysis of data,the correlation between data is sought from the perspective of mathematical statistics.A multi-factor mathematical model is obtained by linear regression and nonlinear regression,and a single-factor mathematical model is obtained by curve fitting.This aspect verifies that the joint action of many factors in the geological environment determines and influences the occurrence of water inrush disasters.It cannot be directly determined by a single variable.(5)Model comparison: Model 1 prediction accuracy is too low and is directly discarded.Model 3 is slightly higher than model 2 in accuracy.For models 5,6,and 7 of single factor,it is only used as a reference value for initial water inrush prediction.According to different geological environments and backgrounds,suitable formulas are selected for rough calculation.From the results,it can be seen that there are 14 relative error rates of prediction model 2 within 0.5,which account for 58.33% of the total,and the relative error rate of prediction results is within 18% of the one order of magnitude,accounting for 75.0% of the entire sample set.This has a strong guiding significance in practical work.