Advanced Materials Research Vols. 243-249

Abstract: This paper takes geological conditions of the Li—Jun expressway by Kang JiaGou and Tong De coal mine goaf as prototype, using the simulation experiment of similar material, simulates the formation process and distribution of the mined rock fracture and the damage variable of the mined rock by using the simulation experiment of similar material, At the same time, It researches the evolvement law of rock’s fracture network in caving zone, fractured zone over goaf using fractal geometry theory. It analyses the damage variable law in caving zone, fractured zone using the damage mechanical theory, and found the relationship of damage variable and mined width. The conclusion of the experiment indicates: with the advance of the working surface, the fractal dimension of the mined rock crack goes through small → large →small, and stable process of change. In the identical push distance of the working surface, fractal dimension of caving zone is 1.0—1.2 times of fractured zone. With the advance of the working surface, damage variable increases gradually, under the identical mined width, damage variable of caving zone is greater than fracture zone, caving zone is about 1.04—1.11 times of fracture zone. Damage variable of goaf central zone is greater than edge.

Abstract: The contribution of surface load to the stability of loess slope should be properly evaluated in order to meet the engineering demand in loess area. It is essential to analyze the stability of loess soil slope by means of the strength reduction finite element method instead of the slices method commonly used in practice so far. Firstly, some researches on stability of loess slope are reviewed. Then some different cases of the mechanism and mode of instability of a loess slope due to surface load are analyzed in this paper. Numerical results not only indicate that the safety factor of loess slope tends to change with the different distribution of the surface load, but also reveal that the distribution of surface load has important effect on the mode of instability of slope.

Abstract: The interface roughness between pile and rock in rock-socketed pile can influence its bearing mechanism largely. At present the numerical simulation, which simulates the interface roughness with changing the surface shape or interface friction coefficient, is used to study the interface roughness’ influence on pile’s bearing mechanism. It can reveal the pile bearing mechanism in some degree; however, there are some defects and limitations in simulation because of its assumptions and simplifications. Based on the pile foundation of Tian-xing-zhou Bridge, the model test is conducted to study the interface roughness’ influence on rock-socketed pile bearing mechanism. In the model test, the surface of model piles are made different ranging from smooth to rough, and the bed rock is simulated with mixture of sand and plaster, the rock-soil overlain the bed rock is simulated with silty sand, the pile is simulated with organic glass rod according to similarity principle respectively. The results show that load-settlement curves grow more gently, the ultimate bearing capacity is bigger, the proportion of point resistance is lower, and the shaft resistance is bigger which reaches more than 70% of total loading as the surface of pile is rougher. The conclusions are useful to deciding the length of pile foundation in Tian-xing-zhou Bridge.

Abstract: The Qing-chun Road Cross-river Tunnel is the first road tunnel under the Qiantang River in Hangzhou, and it is also the first experiences of slurry shield tunnelling in Hangzhou soft ground. In order to ensure the safety of construction and reduction of environmental impacts while shield tunnelling, a comprehensive monitoring system was carried out during construction, which included ground settlements, displacements and deformations of installed linings and so on. In this paper, the long-term ground settlements induced by slurry shield tunnelling were described in detail, and careful analysis of monitoring ground settlements was made. This case study shows that: 1. The surface transverse consolidation settlements do not follow the Gaussian curve; usually the largest settlements exist above the centerline of the tunnel or nearby, from where settlements descend outwards. Due to consolidation, the surface settlement troughs widen with time.2. Shield tunneling in soft ground, the turning point in settlement-time curves or settlement rate-time curves can be chosen as the time divides the immediate and long-term consolidation settlements.

Abstract: Taken the Houchuangzi slope debris flow along Kunming- -Songming highway as instance, analyzed the mineral composition of provenance on the slope debris flow adopted the polycrystal X ray diffractometer, which was rich in hydrophilic clay mineralssuch as kaolinite and montmorillnite; analyzed the fornation mechanism of the HouChuangzi slope debris flow by the laboratory model test, compartmentalized the fornation process of the HouChuangzi slope debris flow in to five stages from the aspects of slope debris flow morphology and crack extension mechanism.The results provide certain reference value for further research of the formation mechanical mechanism.

Abstract: Sand liquefaction is a problem of complex evolution of the disaster, there is no accurate way to judge at present, this study put forward an analytical method to improve and optimize the evaluation system of sand liquefaction based on rough set. The significance of indexes are confirmed by calculating rough dependability between indexes and result for appraisement, the result show that SPT blow count has the greatest impact on the evaluation system, the groundwater level has greater impact, followed by the sand depth, epicenteral distance and duration. The proposed approach overcame the subjectivity of traditional weight determination method, so it is more objective and accurate, and it is reasonable and effective to optimize the evaluation index of sand liquefaction.

Abstract: A physical model test is conducted to study the hydraulic gradient and soil plug development during the suction penetration of bucket foundation in the silts. Furthermore, a FEM simulation is carried out by changing the geotechnical parameters and constitutive model to deeply study the suction penetration mechanism. Through the comprehensive analysis, the results indicate that the seepages inside and outside the bucket foundation are the direct reasons for the formation of soil plugs, and that there are the high hydraulic gradient and the safety mechanism preventing soil flow failure for the silts in the bucket foundation. The seepage changes not only the permeability of soil body but also the physical and mechanical properties, and enhances the rheological property and time effect. Thus, the soil plug failure is not seepage failure, not unloading expansion yet, is a complex deformation failure mode under the protection of safety mechanism of bucket foundation.

Abstract: On the basis of visualization of 3D stratum, deep excavation simulation is accomplished by combining with numerical analytical method, Excavation effect on surrounding environment is analyzed. By using experimental or semi-experimental models, the settlement values and their distribution features, which are caused by excavation, are discussed, by using 3D FEM, the horizontal displacement of excavated foundation ditch is calculated, and the OpenGL technology and triangle split arithmetic are chosen to implement the construction and splitting of 3D strata, the excavating process and its influence on the surrounding environment are ultimately realized. By comparing with engineering cases, the validity of analysis model and implement method are shown to be correct, feasible, and efficient.

Abstract: Based on the law of the spatial distribution, using Monte Carlo technology to simulate joint system, and using three-dimensional solid cutting techniques to build a new rock mass fragmentation prediction model of block three-dimensional interception model. Based on consideration in the joint continuity and the mechanical properties of rock mass, the model simulated the spatial distribution of structure planes according to statistical principles, and predicted rock mass fragmentation using structure planes to cut model prototype and ultimately formed a block muster consisting of cutting blocks. Then, according to a new method of the block shape classification, the distribution statistic rule of internal entities rock block, which are cut out by the structure planes, size and shape are studied. The simulation results show that the fragments with equivalent size of more than 1.65 m account for 40 per cent and those more than 1.26 m account for 59.85 per cent of the total fragment volume.

Abstract: One dimension consolidation equation can be transformed into a fractional differential equation by Laplace transform. The transformed equation can leads to a simple relation between pore water pressure and its time revolution. When local rate of change of the pore water pressure is determined, the local pore water pressure can be obtained without having to solve the consolidation equation within the entire domain. The simplicity of the solution procedure is highlighted considering by a example..