Advanced Materials Research Vols. 261-263

Abstract: The SEM images were obtained from three different sections of the specimens which suffered to one-dimensional consolidation under 5 grade pressures. Basic micro-structure parameters were obtained from these SEM images and their relations with various consolidation pressures were studied. The result indicated that the particle area ratio increase with the increasing of consolidation pressure. Synthesis parameters were studied using principal component analysis. The result showed that the first principle component linearly increased with the increasing of consolidation pressure. When established soil mechanics relation, the Synthesis parameters of micro-structure can be used. That can reflect the integrated character of micro-structure of loess.

Abstract: Different constitutive models is piecewise adopted including modified Cam clay model in cohesive soil and Drucker–Prager model in sand in order to simulate the penetration of jacked piles with ABAQUS more reasonably in layered soil particularly in interactive cohesive and sandy layered soil. Simultaneously, a series of other measures are taken including smoothing the angular corner between the tip and the shaft of a pile in the penetration process, allowing elastic slip even local detachment in pile-soil interface, making the initial stress equilibrium in layered soil come true by means of unconventional multiple calculation and so on. Combining with engineering example, the process of successive penetration of jacked pile in layered soil of having significantly different properties and stiff soil-interlayer in soft soil is simulated and calculated successfully, reflecting the abrupt change phenomenon of stress around pile and jacking resistance. And so the conclusion of numerical analysis is consistent with the in-situ observations.

Abstract: Estuarine area is the intersection zone of river estuary, coastal and land-phase. Cohesive sediment deposition for mutation affects estuary channel transport and brings great challenges to dredging project. Consolidation indicators are closely related to sedimentation and dredging, and there are apparent errors in application of Terzaghi theory in cohesive sediment consolidation evaluation for large stain characteristics. Then it is necessary to modify some consolidation parameters to extend Terzaghi theory in cohesive sediment consolidation. Considering a whole process of sedimentation and consolidation, a unified equation can be established based on sediment deposition and consolidation theory. Equation parameters can be determined by the simulation test (settlement column experiment). According to the settlement curves and volume fraction distribution curves by simulation experiment, modified consolidation coefficient and the trends can be determined, and modified consolidation coefficient can apply in dredging and deposition project.

Abstract: The vertical slice method is generally adopted for calculation of slope stability safety factor. The algebraic expression of the slope stability safety factor Fs is deducted based on the idea of the calculation via the inclined slice method and according to the inclined slice force limit equilibrium conditions. This expression is implicit so that the result can be obtained quickly only through simple iteratives, guaranteeing the convergence. Calculation examples show that the slope stability safety factor Fs derived from this method is very similar with that from conventional methods. which proves that this method is feasible and brings convenience to technical personnel of slope engineering.

Abstract: As the complexity and the tall of open pit slope, two-dimensional slope stability analysis methods have been unable to meet the needs of the accuracy of stability analysis. Therefore, for the complex situation of Pingzhuang open pit slope, use with three-dimensional rigid body limit equilibrium method to analysisstability of slope.slope3D system, which consists of pre-treatment, limit equilibrium analysis solver and post-processing, the first processing core is to construct three-dimensional geological model of the slope, post-processing mainly results analysis and visualization graphics. The system combined organically the slope engineering geological information three-dimensional visualization and the analysis of stability, which make us to determine the landslide model, reveal the mechanism of landslide more accurately. Make an important contribution for ensuring safety in open pit production, a good foundation for slope stability analysis of other open pit.

Abstract: Based on similarity theory, the geologic mechanics model is established and to be used for studying distortion and breakage mechanism of consequent rock slope. The paper introduces the design and process of the experimentation. Through experimentation of a slope model, the stability of a slope is studied. After analyzing the phenomenon and data of the experimentation, it is found that the major deformation model is slippage. The mode of breakage is sliding and fracturing. The process of slippage is graded. The more hinder the position of coast is, the smaller the obliquity of rip face is. The deformation and breakage of bedding slope firstly arises at the dig face near the earth's surface.

Abstract: The causes of water inflow and sand bursting on starting shaft disaster in shield tunnel were analyzed. The analytical model that groundwater seepage from substratum of the reinforced soil to gap in shaft wall on starting shaft in shield tunnelling was established. Using the semi-confined aquifer seepage theory, a practical calculation example was given. The result shows: under the assumption that the reinforced soil was complete exclusion of water, the accidents of water inflow and sand bursting in portal part were influenced by many factors including the length of reinforced soil, groundwater level and so on. The cost and safety of starting shaft engineering had positive correlation with the length of reinforced soil. Lowering the groundwater can significantly reduce water inflow disaster. Comprehensively considered factors of safety, economy, construction period and so on, the reasonable construction parameters can be determined.

Abstract: Pullout force of grouting soil nailing is a key to support. This test revealed that limit pullout force of soil nailing increased with the time. The timeliness function was asked for by Origin software. It's the cause for many failure accidents in soil nailing support engineering. But it was often neglected in engineering design and construction.

Abstract: Rock burst hazard is the main problem of hard rock deep tunnel under high ground stress conditions. The prevention logic of prevention and control of rock burst is proposed by combining local energy release rate index based on the brittle Hoek-Brown model. Stress releasing holes are adopted to lead some energy to release actively and eliminate burst potential of rock burst. Supporting opportunity and parameters were studied by contrasting the magnitude of released energy in FLAC3D numerical software, and then the prevention logic of rock burst is presented. Stress releasing holes relieve stress concentration of the working face, transfer the stress to the deep and reduce the risk of rock burst near the working face. At last, the prevention and control of rock burst for sinping II Hydropower tunnel was analyzed, the results are in good agreement with the actual situations. The proposed method could benefit other deep tunnel projects which have brittle failure.

Abstract: Based on the Drucker-Prager yield criterion which matches with the Mohr-Coulomb yield criterion under the plane strain condition, this paper sets up a cusp catastrophe model of maximum horizontal and vertical displacements to strength reduction factor by using the cusp catastrophe theory. And the catastrophe criterion of slope failure is quantified to the control variable (u) and discriminant (△) which are evaluated by comparing with zero. Taking the above study as the foundation, the cusp catastrophe model is applied to solve one of the standard test ACADS examples. On the two criterions for slope failure of horizontal and vertical displacements catastrophe model, the safety factor of the slope is 0.988 which is consistent with those by ACAS. It shows that the cusp catastrophe model in slope failure analysis is feasible and practical.