Method And Application Study On Interval Response Of Groundwater Head In Two-dimensional Confined Water Flow

There is uncertainty in the numerical simulations of groundwater flow.At present,the stochastic statistical method is one of the major method to study the uncertainty of groundwater flow numerical simulations,and obtains the statistical characteristics of the results based on the statistical characteristics of the model parameters.Due to the limited data,it is difficult to obtain statistical characteristics of the model parameters accurately.The interval analysis method does not require the statistical characteristics of random parameters.The interval response of the groundwater system can be obtained using the non-probability interval analysis model established through bounded but uncertain interval variations.Based on the GFModel program,this study introduces the theory of interval analysis,and proposes a new algorithm to solve the numerical model of interval groundwater flow on the basis of the interval parameter perturbation method.Applying the developed program to solve the steady flow and unsteady flow model of ideal two-dimensional confined aquifer and the numerical model of confined aquifer flow in hydrogeological experimental site in Sanbao.The main results are as follows:(1)The method for solving the interval response of groundwater head is obtained by the interval parameter groundwater head equation established using the natural interval expansion in interval mathematics and the interval parameter perturbation method through the established interval linear equations.In order to verify the effectiveness of the method,there are two ideal numerical models of confined water are established respectively,including the steady flow and unsteady flow.The calculation is carried out by the GFModel program after adding the new algorithm.The results show that the first-order interval parameter perturbation method has the advantages of high computational efficiency and small relative error of the head deviation.This interval method can be used to solve the interval response of groundwater head and analysis the interval uncertainty of groundwater numerical simulation when the statistical characteristics of hydrogeological elements are difficult to obtain but it is relatively easy to obtain the interval range of parameters.(2)This study collected and analysed the hydrogeological conditions and pumping test data of the study area in the wild hydrogeological test site in in Sanbao.The computational results of the established numerical model of the determined groundwater flow and the interval groundwater flow of the study area using the GFModel program for comparison and analysis.The comparison shows that the absolute errors of the two models predicting the groundwater head or the groundwater head extremums are within the error specified by the standard.The results of the interval groundwater flow numerical model contain the interval of the truegroundwater head,and this method has high precision and the engineering feasibility when the change rate of parameters is small.At last,the interval model is used to predict the variation range of the groundwater head of the drawdown of each observation hole under the two extraction conditions.