The main research work is to study the safety state of dam structure by using mathematical and mechanical methods based on dam monitoring data. The specific research contents include the cause analysis of cracks in concrete faced rockfill dam(CFRD), the risk assessment of safety state of CFRD, the randomness simulation of rockfill dam materials, and the safety monitoring of dam seepage and displacement.
Key words: monitoring, crack, CFRD, dam, seepage, displacement
Due to changes in the environmental load and deformation of rockfill bodies, cracks likely form and develop in the face slab of concrete face rockfill dams (CFRDs), affecting the working behaviour of face slabs and the safe operation of dams. Considering that the uncertainty of construction quality leads to the randomization of rockfill material parameters, the probability function and coefficient of variation in the parameters of rockfill materials were determined based on field test data, and then, parameter samples were obtained by Latin hypercube sampling (LHS). LHS and the long- and short-term memory (LSTM) algorithm were applied to obtain the response surface function.
In order to avoid the phenomenon of over fitting and low prediction accuracy of conventional time series model due to not considering the non-linear and random environmental quantity, the integrated empirical mode decomposition (EEMD) method is used to decompose the actual seepage flow monitoring value of water measuring weir, and multiple groups of stable eigenmode functions (IMF) and residual quantities (R) are generated, and then the correlation vector machine (RVM) is used to decompose some of them The IMF series and R are fitted and predicted.
Due to the formation and development of underwater face slab cracks of concrete face rockfill dam (CFRD) during operation period, the working behavior of concrete face slab is affected. In order to reveal the causes of underwater cracks, based on the monitoring data, this paper studied the influence of combined working conditions of unfavorable temperature and water level and construction quality on concrete face slab cracks during operation period, put forward a method to characterize the construction quality by probability distribution function of void fraction, simulated the construction defect area in rockfill area with quality assurance rate, and determined the process of concrete face crack analysis of rockfill dam during operation period. Taking a CFRD as an example, the stress situation and change trend of concrete face slab crack cracking area were studied through structural calculation.
N E.Huang, Zheng Shen. The empirical mode decomposition and the Hilbert spectrum for nonlinear and non-stationary time series analysis [J]. Proc.R.Soc.Lond.1998, 454:903-995.