Applied Mechanics and Materials Vols. 353-356

Abstract: To investigate the influence of surcharge on bearing capacity, model tests were performed. In the tests, 5 kPa and 10 kPa surcharge was applied on silt respectively. The bearing capacity factor Nq is smaller than theoretical solution, and is only of 60.3% and 80.5% of theoretical solution. Model test show that the ground failure mode is not general shear failure mode in condition of ground under surcharge. In bearing capacity calculation, if bearing capacity factor theoretical solution which is from general shear failure mode is applied, the result will be overestimate.

Abstract: A deep foundation pit project in Changsha City covers an area of about 63000m2, the largest excavation depth of the pit is 16.2 m, so it belongs to the deep and large foundation supporting engineering. By comprehensive analysis of the proposed construction site environment conditions and engineering geological conditions the different combined supporting schemes are adopted in different domains separately. In this paper the design schemes of the combined supporting technology are introduced. The problems encountered in the excavation construction process and the corresponding measures being taken are analyzed in detail. The results show that the design scheme is reasonable. Both horizontal displacement and settlement can meet specification and design requirements. At the same time the reasonable construction organization makes the support engineering be finished within the scheduled term, which saves the precious time for the following construction procedure. Furthermore it provides guidance for similar projects.

Abstract: In order to meet the requirements of high-speed train's safe operation, the horizontal displacement of high-speed railway bridge pier top must be strictly controlled. This paper relies on one road construction engineering beneath an existing high-speed railway bridge. We use 2D finite element software to analyze the magnitude and direction of pier top horizontal displacement caused by road load. We take it into account that the effect of the soil nature on pier top horizontal displacement. The analysis showed that the nature of soil around piles of high-speed railway bridge is closely related to the magnitude and direction of the pier top horizontal displacement. Authors believe that the horizontal displacement of pier top consists of two parts. One is pier top pure horizontal displacement dragged by horizontal displacement of the top of piles, the other is pier top rotation horizontal displacement driven by the rotation of pile cap. The analysis result can be used for the design of road with embankment structure beneath high-speed railway bridge.

Abstract: The non-pillar sublevel caving method is used in Iron Mine in Banshi. In the mining area, there are many folds and faults, the inclination of ore body changes greatly, and ore and rock are fragmentized. The tunnel often collapsed and the surrounding rock deformation was getting large during the construction stage. Using the data of tunnel surrounding rock deformation, we adopt the neural network method to set up the mapping relation between the tunnel surrounding rock deformation and the project factors, including tunnel deepness, tunnel dimension, measuring time and surrounding rock quality. The analyzing results show that the maximum error between the forecast and the testing data is 13%, which indicates that this method is useful and feasible to the mining engineering. Key words: rock pressure; measure, deformation of the tunnel surrounding rock; neural network; data normalization; mapping

Abstract: Potential-based fluid model and Westergaard added mass model were used to reflect the dynamic interaction of reservoir-CFRD(concrete face rockfill dam)-foundation coupling system. The deep alluvium deposit was treated as porous medium using Biot's dynamic consolidation theory. In the coupled analysis, the paper focused on hydrodynamic pressures in the reservoir zone, dynamic response and pore water pressure in the structure zone. The result shows that the dynamic response of added mass model is greater than that of potential-based fluid model. The porous medium of alluvium deposit is of great significance in performing soil liquefaction analysis and reservoir-dam-foundation system.

Abstract: According the theory of thermodynamics with internal variables, the relation between yield function and dissipation function and the condition of associated flow rule in stress space are presented; the elastoplastic matrix of the incremental form of the material constitutive equation is given out, this matrix is determined by the free energy function and the yield function. The Gibbs free energy function of solid phase of saturated soils subjected triaxial compression stress state is presented, and using the constitutive theory of thermodynamics with internal variables, yield function and stress-strain relation of the modified Cam-Clay model is obtained by the free energy function and the dissipation function. These results prove the correctness and feasibility for this constitutive theory to construct elastoplastic constitutive relation of saturated soils.

Abstract: While widen the highway foundation, due to it is still unclear that the law of dynamic compaction vibration impact on the original subgrade and foundation structure , which restricts the use of dynamic compaction technology in the highway foundation-broaden project. In this paper, by using the dynamic compaction indoor model test, simulated the dynamic compaction road widening foundation works, monitored the vibration acceleration of the pavement and subgrade surface in the process of dynamic compaction vibration, analyzed the dynamic compaction vibration propagation law of the roadside foundation in the subgrade structure. At the same time, we made the vibration amplitude of the key points and the rammer subsoil dynamic pressure value as double assessment indicators. Besides, we analyzed the dynamic compaction vibration response of subgrade under different parameters, evaluated foundation reinforcement effect. With research, under the same tamping energy and in a certain range of rammer diameter and weight, we had better choose small radius rammer and the compaction process of heavier rammers dropping from lower point, which can reduce the foundation dynamic vibration of the old subgrade and ensure foundation reinforcement effect.

Abstract: The coefficient of compressibility a_v and the coefficient of permeability k_v of clays decrease during the one dimention consolidation process, especially when the strain of clays in the process are large. This paper studies the effects of large strain, decreasing compressibility and decreasing permeability during the one dimention large strain consolidation process by analyzing results obtained from the nonlinear finite element method and comparing with results from the conventional consolidation theory. The research results of this paper shows that the compression index C_c and the permeability change index C_k are two important clay parameters which influence one dimention large strain consolidation process.When the instantaneous load increment remains unchanged, the larger the value of the C_{c ,} the larger the value of the final settlement and the slower the settlement development; the larger the value of the C_k, the faster the dissipation of excess pore water pressure in one dimention large strain consolidation process.

Abstract: High and even super-high embankment filled by red soft soil are often used in road construction in the mountainous areas of Western Yunnan province, China. Due to the poor engineering properties of the red soil, a proper analysis of the stability of the embankment is necessary. This paper aims to analyze the deformation and stability of a typical super-high embankment by comparing the geotechnical centrifuge modeling and FLAC-2D results. The paper finally concludes that: 1) The red soft soil in Yunnan province can be used as fill material; 2) Flat slope and geo-grid can effectively restrain the deformation of the slope; 3) Geotechnical centrifuge modeling well reflect the real engineering performance of the embankment.

Abstract: The relationship between the peak strength of rock masses and joint inclination angle is closely, to study its relationship, experiment on pre-existing persistent jointed rock cylindrical standard specimens was made under uniaxial compression by high stiffness servo control testing machine, experiment found that: the residual peak intensity and peak strength are increased with the decrease of jointed and nonlinear. Analysis on the peak intensity changing with the fissure inclination using Kulun strength theory, theory analysis conclusion is consistent with the experiment, prove the conclusions of experiments and theoretical analysis all can reflect the law of rock masses with transfixion joint failure strength well.