Model construction of dynamic inversion and experimental verification for the void of sluice floor on the soft foundation

As the uneven settlement and seepage deformation of the soft foundation, the floor void is prone to occurring in the sluices built on soft foundation. The traditional non-destructive testing methods are hardly difficult to detect the floor void of the sluices under water, which are non-real time, and their applications still have certain limitations. For the floor of sluice on the soft foundation, it has been under water during the operation period, and new diagnostic methods need to be studied to realize the real-time detection and diagnosis of the floor void of sluice on the soft foundation. The floor void of sluice on the soft foundation will cause the overall constraint boundary conditions of the sluice to change, thereby changing the overall modal parameters of the sluice. The diagnosis of the floor void of sluice on the soft foundation can be realized by establishing the nonlinear mapping relationship between the modal parameters and the floor void parameters of sluice. The method of diagnosing the floor void of sluice on the soft foundation based on modal parameters can realize real-time detection well. Therefore, a dynamic inversion method of the floor void of sluice on the soft foundation is proposed on the basis of the indoor physical model of the sluice on soft foundation in this research. First, based on mathematical model of multi-parameter variables of the floor void of sluice, a mathematical proxy model reflecting the nonlinear mapping relationship between the void parameters of the sluice floor and the dynamic parameters (modal parameters) of the sluice was improved. Second, the combination of the change rate of multi-order frequency and mode shape of multiple measurement points of the sluice was took as the dynamic sensitive characteristic quantity of the parameters inversion, and an objective function for the dynamic inversion of void parameters of sluice floor was established. Then the objective function is optimized through the genetic algorithm. Finally, a physical model of the indoor sluice on soft foundation had been made, and three different conditions of floor void of sluice on the soft foundation were set in the model. The prototype vibration test of the physical sluice on soft foundation on three conditions was carried out, and the corresponding modal parameters of sluice were identified based on the vibration response signal. And the dynamic inversion method of the floor void of sluice on the soft foundation proposed in the paper was used to invert the floor void of sluice and verified by the physical model. The results showed that the trend of floor void of sluice and the void area determined by the inversion method based on dynamic parameters of sluice were in good agreement with the actual condition of the physical model. With the three different conditions, the relative errors between the calculated void area and the actual void area are 7.47%, 6.78%, and 6.90%, respectively, which can confirm the reliability and rationality of the proposed method. The proposed method can provide a new idea for safety detection of the floor void of actual sluice on the soft foundation.