Research On The Inverse Method Of Material Parameter For Concrete Gravity Dams

Inversion of dam material parameters by displacement observation data has been widely used in water conservancy engineering and geotechnical engineering and other fields. Inversion of material parameter for concrete gravity dams can not only revise the original design, but also monitor the running state of dam safety, response the working behavior of the dam. Because of this, study on inversion of dam material parameter has always been the focus topic for the foreign and domestic scholars. This paper lists some inversion methods of material parameter after summarized the existing literature. Established an object function according to the displacement back analysis method, the gradient search method was proposed to optimize the aim function. In view of the disadvantages in calculation of sensitivity matrix, a formula was derived to calculate it. Since the error contained in the observation values will lead to the ill-posed problem of inversion analysis, the regularization method was used to solve this problem. This study is mainly to find a stable and practical inversion method, so that it can be used to assess the integrity of concrete gravity dams. The main work of this paper is the following aspects:(1)The traditional regression factor was supplemented by using the integral regression method, the regression results has higher fitting accuracy after supplemented factors than before. Separated the water level displacement component of the crest observation point by using the stepwise regression analysis method;(2)Established the aim function using the water level displacement component, the solving progress of partition elastic modulus becomes an optimizing problem of the objective function. The basic principles and steps of the gradient search method was introduced, a formula found through the derivation is proposed to calculate the sensitivity coefficients, the coefficients calculated through this method is more accurate than the difference method did, the feasibility of the method is validated by the project examples;(3) The observation noise is inevitable in safety monitoring data, the reason why observation noise would lead to the ill-posed problem was introduced in this paper. The method of applying regularized factor in parameter inversion was adopted to solve the ill-posed problem. Here proposed a regularization inverse method of material parameter for gravity dams. The L-curve criterion was used to determine the optimal regularization parameter. The sub-regions’ elastic modulus of Fengman dam were inversed through using regularization method according to observation data. Through comparing the inversion results with the field corning results, we proved that this method can be used in engineering practice.