The seepage parameters of the dam body and dam foundation are difficult to determine accurately and quickly. Based on the inverse analysis, a Gray Wolf Optimizer (GWO) was introduced into this study to search the target hydraulic conductivity. A novel approach for initialization, a polynomial-based nonlinear convergence factor, and weighting factors based on Euclidean norms and hierarchy were applied to improve GWO. The practicability and effectiveness of Improved Gray Wolf Optimizer (IGWO) were evaluated by numerical experiments. Taking Kakiwa dam located on the Muli River of China as a case, an inversion analysis for seepage parameters was accomplished by adopting the proposed optimization algorithm. The simulated hydraulic heads and seepage volume agree with measurements obtained from piezometers and measuring weir. The steady seepage field of the dam was analyzed. The results indicate the feasibility of IGWO in determining the seepage parameters of Kakiwa dam.

The calcium leaching effect inevitably increases the grout curtain hydraulic conductivity. It is diffucult to sample and obtain the leaching-related calculation parameters for deep-buried grout curtains. This study introduced the inversion method into the calcium leaching analysis to get proper leaching-related calculation parameters and accurate results. An inverse analysis model was proposed using the genetic algorithm (GA) and finite element analysis technology to solve the calcium leaching problems. The objective function is constructed using the hydraulic head and leakage quantity time-series measurements, which improves the uniqueness and reliability of the inverse results. The proposed method was applied to the inverse analysis of the hydraulic conductivity evolution of the grout curtain in a concrete dam foundation. The predicted water heads and leakage quantity are consistent with the monitored data, indicating the rationality of this simulation. The grout curtain hydraulic conductivity prediction in 100 years is also presented. The results illustrate the feasibility of the proposed method for determining leaching-related parameters and the hydraulic conductivity prediction in the leaching process.

The calcium leaching effect leads to a decrease in the impermeability of the impervious curtain. The inverse analysis strategy was introduced in this study because the calcium leaching parameters of the curtain are not easy to determine. An orthogonal design and the finite element method were used in the strategy. The time-series data of hydraulic head and leakage volume were applied to construct the objective function. The extreme learning machine (ELM) was proposed to build the reflection sets. Genetic algorithm (GA), simulated annealing (SA), sparrow search algorithm (SSA), and particle swarm optimization (PSO) were employed to accelerate the iterative search for the target parameters. The target parameters of the calcium leaching model were used for finite element verification by comparing the monitored and simulated values. The simulated values of hydraulic head and leakage by PSO show good agreement with measurements. The evolution of the curtain permeability coefficient in 100 years was analyzed. The results demonstrate the strategy’s feasibility in determining the curtain’s calcium leaching parameters and permeability coefficients.

Seepage is the primary cause of dam failures. Conducting regular seepage analysis for dams can effectively prevent accidents from occurring. Accurate and rapid determination of seepage parameters is a prerequisite for seepage calculation in hydraulic engineering. The Whale Optimization Algorithm (WOA) was combined with Support Vector Regression (SVR) to invert the hydraulic conductivity. The good point set initialization method, a cosine-based nonlinear convergence factor, the Levy flight strategy, and the Quasi-oppositional learning strategy were employed to improve WOA. The effectiveness and practicality of Improved Whale Optimization Algorithm (IWOA) were evaluated via numerical experiments. As a case study, the seepage parameters of the Dono Dam located on the Baishui River in China were inversed, adopting the proposed inversion model. The calculated seepage field was reasonable, and the relative error between the simulated head and the measured value at each monitoring point was within 2%. This new inversion method is more feasible and accurate than the existing hydraulic conductivity estimation methods.

During earthquakes, seismic ruptures propagate (Vr) along faults as mode II-III cracks, approaching the shear wave speed Vs (i.e., sub-Rayleigh or Vr ~ 0.9 Vs), or, in at least 15% cases, at Vr faster than Vs (i.e., supershear or Vr ~ √2Vs ) (Bao et al., 2022). Since ground shaking increases with rupture speed, the transition from sub-Rayleigh to supershear speeds is critical in seismic hazard studies. This transition may occur (1) directly, due to dynamic stress perturbations associated with stress and strength heterogeneities along the fault, presence of fault step-overs and damage zones, etc., or (2) in-directly, where the stress peak ahead of the main crack tip (mother crack) nucleates a secondary crack (daughter crack) once the local fault strength is exceeded (Burridge-Andrews model).Here we employ a newly-conceived 2-dimensional hybrid Finite Element Method and Peridynamic (FEM/PD-2D) model to simulate crack propagation and investigate the transition from sub-Rayleigh to supershear in dry and fluid-saturated media, where the Finite Element Method is used to simulate fluid flow, while Peridynamics is used to describe solid deformation. The model also incorporates a novel bond failure criterion based on critical rotation deformation (i.e., deflection angle of the Peridynamic bonds before and after shear deformation) for mode II fracture propagation.First, we validate the FEM/PD-2D model against previous results from (1) numerical simulations with ABAQUS by Yolum et al. (2021), and (2) physical experiments with PMMA by Svetlizky et al. (2015). In case (1), the FEM/PD-2D model accurately reproduces rupture propagation in a dry Homalite plate with a pre-notch subjected to impact shear loading. Supershear rupture is recognized by the emergence of shear Mach waves observed in the particle velocity magnitude contours. In agreement with Yolum et al. (2021), the stable supershear crack velocity lies between √2Vs and Vp (compressional wave speed). In case (2), the model reproduces the shear loading experiments of PMMA blocks with a frictional interface, and yields crack growth curves and supershear propagation consistent with the measurements of Svetlizky et al. (2015).Subsequently, we apply the FEM/PD-2D model to explore rupture propagation along both dry and fully saturated media under shear loading. Supershear crack speeds and the emergence of shear Mach cones are observed in both the dry and fluid-saturated cases. Supershear rupture can be achieved through either the in-direct (Burridge-Andrews mechanism) or a direct transition. Notably, the presence of the fluid phase enhances the sub-Raileigh to supershear transition due to poroelastic effects at the rupture front. The findings from this model, beyond their implications for earthquake hazard assessment, may also explain the formation mechanisms of hundred-meter-thick rock damage zones adjacent to seismogenic faults.