New deformation back analysis method for the creep model parameters using finite element nonlinear method

Creep deformation of rockfill and overburden affect anti-seepage systems, such as face slabs, toe slabs, and peripheral joints, which may cause structural damage, particularly in a high concrete-faced rockfill dam (CFRD) on a deep overburden layer. The deformation mechanism of rockfills is complex. It is difficult to determine the creep deformation characteristics completely with creep test. Back analysis based on measured data inversion is an effective approach to study the long-term deformation characteristics of CFRD. In this paper, a new deformation back analysis method called MPSO-BP, which integrates a modified particle swarm optimization algorithm and neural network simulator, is presented to reverse the creep model parameters of Jiudianxia CFRD based on the plate load test, pressure test, and large-scale triaxial test. The creep model parameters of rockfill and overburden are applied to analyze and forecast the long-term deformation characteristics of the CFRD by using 3D nonlinear finite element numerical analysis method. Results show that the calculated creep deformations are agreed with the monitoring data. The back analysis method and the inversion parameters are demonstrated to be reasonable. The deformation of the CFRD tends to stabilize after the dam reservoir reaches its tenth year of operation.