Based on the distinct element method, a numerical procedure is presented for simulation of creep behavior of jointed rock slopes due to excavation unloading. The Kelvin model is used to simulate viscous deformation of joints. A numerical scheme is introduced to create incremental contact forces, which are equivalent to producing creep deformation of a rock-joint system. The corresponding displacement of discrete blocks due to creep deformation of contact joints can be calculated by equilibrium iteration. Comparisons of results between the numerical model and theoretical solutions of a benchmark example show that the presented model has excellent accuracy for analysis of creep deformation of rock-joint structures. As an application of the model, residual deformations of the high rock slopes of the Three Gorges shiplock due to excavation unloading and creep behavior are investigated. By simulating the actual excavation process, the deformation history of a shiplock slope is studied. Good agreement has been achieved between numerical prediction and field measurements. It demonstrates the effectiveness of the presented model in analysis of the creep deformation due to excavation unloading of high rock slopes.

A procedure is presented for the analysis of the stability and propagation of cracks in arch dams based on linear elastic fracture mechanics and three-dimensional boundary element modeling. A simplified crack propagation criterion is employed and the crack trajectories arc obtained by multistep extension. The first up stream cracking which occurred in the Kolnbrein arch dam is studied in detail under various conditions conceming the foundation interface, location of crack initiation, reservoir water level and load combinations. Crack trajectories close to the observed one are obtained with water level at 1, 850-1, 860m, which agrees with the prototype experience. It is found that the hydrostatic load and associated uplift pressure on the crack surfaces are the key factors for causing an initial crack at the dam base to propagate to the upstream face. It is also noted that the bonded condition at the interface between the dam and the upstream elevated foundation is responsible for producing the distinctive profile of the observed crack, which daylights on the upstream face at an acute angle.

Comprehensive studies on the dynamic behaviours of a high rock slope of the Three Gorges shiplock and a blocky arch structure are performed using the distinct element method (DEM). Some additional functions have been incorporated into the current DEM code, including a scheme of non-uniform seismic input on the boundaries and an improved triangular mesh generator for deformable elements. Parameters from the field and laboratory tests of the project are used in the analysis of the shiplock slope. Comparisons between the DEM results and the field measurements under the excavation unloading process are made and the good agreement obtained demonstrates the effectiveness of the DEM for predicting the deformation process of the slope. The above examples of the high rock slope and the blocky arch demonstrate that the effects of different earthquake input, input mechanism andparameters on the dynamic response behaviours and collapse pattern of the systems are significant.

A coupling model of Finite Elements (FEs), Boundary Elements (BEs), In

coupling procedure of finite element (FE) and scaled boundary finite element (SBFE) is presented for three-dimensional (3D) dynamic analysis of unbounded soil-structure interaction in the time domain. The procedure is implemented with the following efficient techniques: (1) Based on the concepts of linear system theory, the acceleration unit-impulse response matrix of the unbounded soil calculated by the SBFE method is converted into a group of time-independent matrices; thus, the time history of the unit-impulse response function of the unbounded medium can be replaced by an equivalent state-variable description. (2) The interaction forces between the unbounded soil and the structure are evaluated by a system of linear equations instead of time-consuming convolution integrals. (3) Since only the partial information of the unit-impulse response function is sufficient to capture the main character of the unbounded medium and the history of response function can be truncated at the cut-off time tc, the computational effort spent in the SBFE method can be further reduced. In addition, the accuracy of the procedure can be controlled with prescribed parameters, thus the main advantage of the SBFE method as a highly accurate procedure is retained. Three numerical examples of foundation response demonstrate that good agreement can be achieved when compared with previous results, and high efficiency is also evident compared with the direct convolution integral method. Copyright