Based on the fundamental solutions due to Dirac's d function for transversely isotropic media, a numerical scheme for wave propagation in two-dimensional orthotropic media is developed within the boundary element method in the time domain. Criteria for selection of the time and space discretizations for convergent and accurate results are established. The applicability and accuracy of the scheme are verified by a number of benchmark problems including dynamic responses of an orthotropic half plane under uniform harmonic surface loadings and a circular cavern in slightly orthotropic media under the incidence of pseudo-P and-SV waves. The procedure is then applied to examine wave propagation for an underground tunnel with different ratios of orthotropy in the media. The effects of different wave parameters and ratios of orthotropy on dynamic response of the tunnel are presented.

Based on the dynamic theory for saturated porous media by Biot (Journal of the Acoustical Society of America 1956; 28:168–178), a numerical model is presented to analyse the resection behaviours of reservoir sediment and compared with those from the visco-elastic model. It is concluded that the two models give very similar results of resection coefficient α within the frequency range of interest. Then, using the two models, the change of the resection coefficients α with various sedimentation parameters and excitation frequencies are studied in detail. The results are further used in the analysis of response functions of hydro-dynamic pressures on, and structural displacements of the Xiang Hong Dian arch dam, for which some results from a Celd vibration test are available. It appears that e2ects of water compressibility with sediment resection on hydro-dynamic pressures and structural response are not signiCcant for this speciCc case. Copyright

A comprehensive study of non-linear seismic response of arch dams with contraction joint opening and joint reinforcements has been conducted. A numerical model of contraction joint reinforcements is presented for optimization control of the joint opening. The objective of this control is to reduce the joint opening and expectantly to balance the sustained loads between the horizontal and the vertical components of the dam, thus avoiding an overstress in the cantilever while retaining the release of arch tensile stresses to some extent. Several parameter studies such as critical element size and required number of joints to be simulated for convergence are also performed. As an engineering application, a 292-m high arch dam (the Xiaowan arch dam) and the Big Tujunga dam are analysed in detail. The results demonstrate that the joint opening and the corresponding load transfer from the arch to cantilever components of the dam during strong earthquakes are substantial. It is also evident that by providing su$cient strength and reinforcement #exibility, the joint opening can be controlled to some extent. However, the stress redistribution due to reinforcement control is not su$cient to avoid the overstress in the cantilever for the Xiaowan arch dam. Thus, alternative measures are discussed. Copyright

Strain controlled uniaxial tensile and compressive tests of rolled compacted concrete ~RCC! are conducted to establish the constitutive relationship of RCC. Complete stress-strain constitutive curves including strain-softening behavior of the material have been obtained. To satisfy the test requirements for obtaining the strain-softening behavior of the material, the stability conditions on specimen parameters and machine rigidity are described based on the concept of strain localization. By using test results of RCC, a 200-m high RCC gravity dam, Longtan Dam, is analyzed for earthquake resistance using the procedure of nonlinear fracture mechanics and the compression-shear failure mechanism for concrete. A safety evaluation of the dam's ability to resist the design earthquake under different reservoir elevations is performed.

The earthquake behavior of arch dams is studied including dam-canyon interaction and nonlinear response of dams due to contraction joint opening and joint reinforcements. Significant effects of canyon radiation damping, non-uniform free-field excitations and nonlinear joint behavior on dam response have been confirmed.

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