Advanced Materials Research Vols. 243-249

Abstract: The influences of the ways in which the surface cracks were made and fillings in the surface cracks on the fracture behavior of the jointed rock masses were studied by a number of experiments. In the experiments the surface cracks were made in different methods such as placing polyester and aluminum thin plate, cutting. The experiment results show that the surface crack made by placing polyester thin plates and cutting may well simulate the natural cracks in jointed rock masses, but the specimens can’t initiate and fracture through the surface cracks formed by placing aluminum thin plate. In order to study the influences of the fillings in the cracks on the fracture behavior of the jointed rock masses polyester and aluminum thin plates were placed in the surface cracks to simulate different fillings. Compare with the surface crack without fillings those with fillings initiated and coalescence at a higher load. However the influences of fillings on the crack growth were very complex, which required to be studied further.

Abstract: Dynamic Poisson’s ratio is a very important parameter for the numerical analysis of dynamic responses in a rock-fill dam. It is generally taken as a constant of which the significance is generally underrated. In order to have a better understanding of the dynamic properties of rock-fill materials, a series of tests were performed to investigate the effects of the shear strain on the dynamic Poisson’s ratio. The experimental results show that dynamic Poisson’s ratio varies with the shear strain, the dynamic shear modulus and the confining pressure. In addition, the empirical formulas to determine the dynamic Poisson’s ratio with the shear strain or normalized shear modulus are given in this paper.

Abstract: DX pile is a newly developed variable cross-section pile. Compared to conventional straight pile, it has distinct advantages on bearing capacity and settlement control. However, the bearing mechanism and characteristics of settlement, especially on group DX piles, are not clear. This paper illustrated and analyzed the bearing capacity and settlement characteristics of single DX pile and group DX piles according to the test results of in-situ model test. Special attention was paid on single and group DX pile comparison under same circumstances, at the mean while, compared the single DX pile and conventional pile with the same pile length and diameter, and with the same bearing capacity. The conclusions from the test results provided theoretical references for the design of the DX piles in engineering practices.

Abstract: The soil-water characteristic curve (SWCC) is one of the major research subjects in unsaturated soil mechanics. To study the influence of deviatoric stress on the SWCC of an unsaturated soil, a series of triaxial drained shear tests by controlling constant net mean stress and suction were conducted. It was found that the SWCC was dependent on deviatoric stress. A unified SWCC equation was proposed including not only water content and suction, but also net mean stress and deviatoric stress.

Abstract: A series of triaxial shear tests on unsaturated intact loess were conducted using CT-multi-function triaxial apparatus. The distinct CT images and relevant CT data were obtained nondestructively during triaxial shear. CT data was used to define a structure parameter and an evolution variable which characterized the evolution of meso-structure. An equation is proposed to describe the evolution of meso-structure of unsaturated intact loess during loading, which reflects the influences of net cell pressure and suction on the evolution of meso-structure.

Abstract: Based on the model test, ABAQUS, the large-scale nonlinear finite element software was applied to build the numerical simulation model of the reinforced cement mixing wall in soft soil. The model parameters were obtained and the model was optimized with the technique of parameter inversion. Based on equivalent principle, the equivalent model was built to study the Cement's Stiffness-Contribution in reinforced cement mixing wall and its equivalent Stiffness was obtained. Analysis shows that the presence of cement can increase the core pile stiffness by 13.2%.

Abstract: To understand the strength behavior of solidified waste matrices as building materials, sewage sludge as a kind of municipal solid waste had been solidified/stabilized by a binder constituted of Portland cement and stone material powder. Based on the experiment data, a mathematical model relating the strength gain of solidified sludge matrices to the ratio of binder to waste is proposed by statistical analysis. The proposed method is then verified with available test data.

Abstract: With increase of terrorist blast, it is becoming more important for buildings to resist the blast load than before. This paper focuses on analysis of loss influence on key members of frame structures subjected to blast loading. The performance of a 5 storey frame structure with damage was evaluated on the assumption that whose key columns and beams had been lost after blast. By comparing the deformation and the internal force of the original frame with the corresponding items of the incomplete one, the impact of the key columns or beams on the performances of the whole frame structure was discussed. Numerical results show that the loss of either the key columns or the key beams will endanger the whole structure. Especially, the deformation and the internal force of the members adjacent to the missing key column have obvious increases. Consequently, the loss of the key column exerts a more serious impact on the building than that of the key beam.

Abstract: A back analysis procedure synthetically using parameters sensitivity analysis based on orthogonal design variance analysis, support vector regression modeling of nonlinear relation between mechanical parameters and displacement, and a hybrid optimization algorithm of particle swarm optimizer (PSO) and differential evolution (DE), was proposed. Optimum values of elasto-plastic mechanic parameters of rock mass were identified using the back analysis procedure and the measured displacement data. Assigning to the numerical model the optimum values of parameters, numerical simulation of powerhouse construction process was carried out to investigate the reliability of result of back analysis and the stability of powerhouse cavern. The result shows that calculated displacements are in good agreement with the measured, the powerhouse cavern is stable and has a considerable safety margin, and the existing support system can satisfy the need of local stability of powerhouse.

Abstract: In recent years the rock-socketed continuous concrete walls have been applied in supporting structure of foundation excavation, and the main problem of which is how to simulate m value of wall bottom bedrock. In this paper, the m value of rock-socketed underground continuous concrete wall bedrock is monitored by a structural test about a typical engineering. The monitored data of foundation excavation supporting deformation are fitted by least-square method, and the bedrock m value of which are researched and analyzed based on an optimization method and fitting deformation curves. The test shows the monitored m value meets the corresponding engineering regulations and is related with the broken degree of rock on the monitored position, and the variability of which is lesser in the construction process.