Zhenzhong Shen

Back analysis of the 3D seepage problem and its engineering applications

The main purpose of seepage control in dams is to prevent dams and other foundation abutments from being destroyed by seepage erosion. This control is important for safe and efficient maintenance of hydraulic and geotechnical engineering structures in the reservoir areas. Back analysis of a seepage field based on measured data is an effective way to determine the initial distribution of the seepage field, which is essential for seepage control planning and implementation of safety measures. In this paper, a back analysis method and super-equivalent continuum model were used to analyse the natural seepage field parameters and seepage field analysis in the construction zone of the dam. The results of previous analyses of the seepage field and seepage control measures provided the basic parameters and model foundation; back analysis was used to determine the boundaries of the groundwater and the calculation parameters, modify the boundary conditions of the dam foundation excavation pit, and obtain the seepage field during the construction of the hub area. The results of the back analysis show that the natural groundwater distribution simulation is generally consistent with the field data, indicating that the finite element model is an important tool for simulating the engineering geological conditions of the dam area and rock mass permeability partition.

A Hybrid Finite Volume and Extended Finite Element Method for Hydraulic Fracturing with Cohesive Crack Propagation in Quasi-Brittle Materials

High-pressure hydraulic fractures are often reported in real engineering applications, which occur due to the existence of discontinuities such as cracks, faults, or shear bands. In this paper, a hybrid finite volume and extended finite element method (FVM-XFEM) is developed for simulating hydro-fracture propagation in quasi-brittle materials, in which the coupling between fluids and deformation is considered. Flow within the fracture is modelled using lubrication theory for a one-dimensional laminar flow that obeys the cubic law. The solid deformation is governed by the linear momentum balance equation under quasi-static conditions. The cohesive crack model is used to analyze the non-linear fracture process zone ahead of the crack tip. The discretization of the pressure field is implemented by employing the FVM, while the discretization of the displacement field is accomplished through the use of the XFEM. The final governing equations of a fully coupled hydro-mechanical problem is solved using the Picard iteration method. Finally, the validity of the proposed method is demonstrated through three examples. Moreover, the fluid pressure distribution along the fracture, the fracture mouth width, and the pattern of the fracture are investigated. It is shown that the numerical results correlated well with the theoretical solutions and experimental results.