Advanced Materials Research Vols. 261-263

Abstract: A numerical model of Transient Electromagnetic Methods, which used to detect geological conditions in tunnels, was created by ANSYS finite element software, and the transient electromagnetic response characteristics of typical unfavorable geological bodies were discussed. The results indicate that the apparent resistivity isoline almost outputs in straight structure, and augments equably with the depth increasing when no unfavorable geological body is in front of the tunnel workface. The apparent resistivity isoline obviously reduces when water-rich karst cave, fault, or fracture exist in the front of the tunnel workface, where water-rich karst cave exists, the apparent resistivity isoline becomes close together, and there is to be an ordered pyramid resistivity-reduced area which can be an evidence of rich water fault. However, it will increase when dry fault or karst cave exist, and the high resistivity area corresponding to dry cave shows some triangles, but this phenomena is hard identified, which need detail analyses according to hydrogeologic data.

Abstract: Based on Biot’s wave propagation equation and boundary conditions, this paper builds up pile group and soil system used for calculation in 3 dimension models, though mass conservative and motion equation. The results of ground surface movement are obtained under the effect of vertical dynamic force though Newmark direct integration. Compared with the measured results, the numerical outcomes conform accurately. The calculating results show that vibration of ground surface can be affected by several parameters such as soils’ possion ratio, permeability coefficient, different types of pile groups and so on. Different factors have different effects on ground’s surface vibration in both far field and near field.

Abstract: The large bedded slopes are the common engineering geology in mountain areas. In this paper, the influence factors, including the gradients, slope length, thickness of slide body, of the large bedded slopes were analyzed. The influence laws of the toe segment slippage length of the factors were obtained and the computing formulas of the toe segment slippage length were presented. The computing formulas were validated by the data of field survey. The results indicated that the toe segment slippage length which were determined by the slope length (L), thickness of slide body (H) and slope gradient (α) were according with the field survey and had the better safety coefficients.

Abstract: In the design of deepwater foundation for bridges, the interaction between water and the structure especially under earthquake motions should be addressed. This paper presents a practical simplified method to analyze deepwater pile group foundation to determine its dynamic characteristics by combining approximate analytical solutions with the finite element method. The applicability of this proposed method is shown in a case study of a nine-pile foundation. Compared with those from complete numerical method, the analysis results from this simplified method are in agreement when the pile cap is not submerged in water. Furthermore when ignoring the vertical hydrodynamic added mass of the pile cap, the vertical vibration mode results are greatly affected, but not for other non-vertical vibration modes. This simplified method is also used in the study of the influence of water on the dynamic characteristics. The deeper the water is, the more obvious the impact of water is, particularly for the pile cap lateral bending modes, and there appears no evident difference for the pile lateral bending modes, on which water effect is stronger than that on pile cap lateral bending mode.

Abstract: To reveal the mechanical property on the interface between the surrounding rock and the supporting structure, inducting the definition of the interface, based on ABAQUS software, two finite element models were established to compare and analysis the interaction through the aspects of stress, deformation and plastic region of surrounding rocks and the resistance of supporting structure. At last, compare the simulative and the metrical results. The result shows that the ideal full-constraint between the surrounding rock and the supporting structure isn’t possibility. It becomes more reasonable to define an interface during the numerical analysis and design calculations, the selection of the constitutive relation of the interface is directly related to the accuracy of the numerical calculation results.

Abstract: Based on the theory of sensitivity analysis, the local/global sensitivity analysis of parameters for the modeling of thermal transport in aquifer under special groundwater flow and heat source conditions were carried out with the summer running of Groundwater Source Heat Pump (GSHP) system as a study case, by taking the temperature of typical observation points and thermal affected zone (TAZ) of injecting water at the end of summer as the model outputs. The results showed that the sensitivity of each modeling output was various for the different parameter in local analysis. The orders of local sensitivity coefficients of the nine parameters for two modeling outputs were almost coincident. In global sensitivity analysis, the sensitivity of the parameter being investigated was influenced by the different values of other parameters. The two modeling outputs almost had the same variation tendency of global sensitivity with different parameter combinations.

Abstract: Field soil investigation prior to the foundation design of any structure is a must for the design engineer. Since the cost of such operation is rather high, then it is sometimes impractical. The design and the preliminary cost estimation of the construction are then impossible to be prepared. This paper applies Geographical Information System – GIS via Google earth to all over Bangkok area thus enables engineer to retrieve the physical characteristics of soil layers from the existing soil data. In addition, utilizing the feature of Google earth can be illustrated more visibility in the required position of boring log and position of retrieved soil boring log data. Moreover, it can be applied to everywhere around the world.

Abstract: The consolidation of the composite ground under non-uniformly distributed initial excess pore water pressure along depth was studied in two models which respectively considering both the radial and vertical flows in granular column and the vertical flow only in granular column, and the corresponding analytical solutions of the two models were presented and compared with each other. It shows that the distribution of initial excess pore water pressure has obvious influence on the consolidation of the composite ground with single drainage boundary, and the rate of consolidation considering the radial-vertical flow in granular column is faster than that considering the vertical flow only in granular column.

Abstract: Based on the principles of conventional oedometer tests, half mold consolidation apparatus which attained Chinese Patent Certificate of New and Practical Device was designed for non-saturated soil's micro-observation with axial drainage conditions. By half mold consolidation tests, we could get similar stress-strain curves at different water content, which could illustrate the feasibility of the new apparatus. Besides, on the application of DPDM (the digital photogrammetry for deformation measurement) technology, the deformation fields of the silty clay were analyzed under monotonic increasing load, which could obviously show the macro mechanics properties by digital image analysis. According to the distribution of deformation fields, the analyzing area could be divided into three parts from top to bottom sequence: soil in top area subsided with upper porous-stone in balance; the deformation in the central area was changing the most whereas there had always been inapparent changes near down porous-stone. Such study could put forward a new conception for the development of conventional soil tests, which could be helpful to further establish the theoretical constitutive model for silty clay.

Abstract: By analyzing the association relationships between sand particle mechanics parameters and microscopic characteristics, this paper qualitative establishes the association table including physical and mechanical parameters such as the water content w, void ratio e and shear stress, and micro-parameters of sand particle such as particle number n, long axis L, short axis B, x, y coordinate of the centroid of particle, y-axis projection length, degree of eccentricity and orientation arrangement. Then the macro-micro relationship table of sand was established. The macro-micro relationship table of sand indicated that three micro-parameters of sand particle including particle number n, long axis L, short axis B have closely relationship with the water content w, void ratio e and shear stress. And the qualitative research between the sand particle mechanics and microscopic characteristics laid the foundation for the macro-micro association research.