Applied Mechanics and Materials Vols. 170-173

Abstract: Based on saturated-unsaturated seepage mechanism, the features of pore-water pressure, strain and displacement of fissured and fissureless slope are analyzed by using the finite element method. At the same time, pore-water pressure, displacement and safety factor of fissured and fissureless slope as well as fissured slope with different depth and width are comparatively analyzed under the condition of rainfall and evaporation. The research results show that, under rainfall condition, the existence of fissures could change the boundary of soil infiltration and seepage filed distribution, lead to stress concentration and make plastic strain around the fissures area. In addition, as the rainfall response time increasing, the plastic zone around the fissures will spread to the surrounding, thus, the new micro-fissures would be produced during the process of the fissures expansion. Evaporation will reduce the shallow soil water content, increase suction and slope stability. Under the condition of rainfall and evaporation, slope stability is affected more seriously by the fissure depth, but less by the width.

Abstract: The finite element method has been used widely in foundation pit engineering to simulate the deep foundation excavation, but it is troublesome and time-consuming to get the important calculation parameter of the soil elastic modulus. So a method based on the comon soil parameters is proposed to get the soil elastic modulus. And a real foundation excavation was simulated using the finite element software ABAQUS and the soil elastic modulus got according to the proposed method. The three-dimensional finite element analysis results were compared to the field data, and both results were close to each other.

Abstract: First, the constitutive equation of the linear elastic and the basic equations flexibility of the unloading rock mass were introduced, and then using the equations and the boundary conditions the variation principle was contracture. Prior to construct an appropriate minimum potential energy functional, on this basis, pending the introduction of two Lagrange multipliers, and absorb the variation constraints to establish the new functional. Last will 、、、as an independent variable, considering the variation stationary conditions functional of the new functional can identify the Lagrange multipliers 、 to be determined, so can build the generalized variation principle of dual variables

Abstract: The direct roof of B132 coal seam is conglomerate layer in a coal mine, which is cemented with gravels and sandstones and has brought great difficulty for tunnel supporting. It is necessary to study the grain size and strength characteristics of gravel in conglomerate layer for the mining of B132 coal seam safely and efficiently. The statistics and analysis of grain-size characteristics of gravel was carried out in this paper, including of the quantity and volume percent of gravel. Uniaxial compressive strength of gravel was tested with point load method. The test results show that uniaxial compressive strength of gravel is very high, especially the black gravels, whose compressive strength is commonly above 200 MPa and the highest even can reach more than 300 MPa.

Abstract: The measured data and mechanical parameters were considered unknown but bounded property and interval numbers were used to denote the measured data and mechanical parameters. The interval parameter perturbation method was presented to solve interval FEM and the interval inverse analysis model was established. Based on the interval parameter perturbation method, the mean and deviation of the mechanical parameters were obtained by the back analysis. For the example of the mechanical parameter back analysis of rock mass cave in the large hydro-electric power station, the effect on the measured data precision was studied. From the results it can be found that the method is reasonable and feasible.

Abstract: The backward blasting of the mine technology and stoping technology will lead to a long time of blasting, high labor intensity and low production efficiency, which also cause roof collapse and the blast of fly rock, support fall and overthrowing the chain-trigger, which cause a larger hidden of production. Through using the mechanical mining technology of the high yielding and efficiency of kaolin, which fundamentally improve the working conditions of workers and safety working condition, will laid the foundation for the increasing of production and efficiency. The production has been promoted from 250-300t/d to 550-650t/d now, which the efficiency is increasing more than 120%. Meanwhile, the optimal of blasting parameters is benefit to roof control after blasting, which can improve the efficiency of blasting, reduce the unit consumption of dynamite, which can save about 0.115kg/ m3; and reduce the intensity of the workers and the damage of the support. This construction technique can provides a reference significance for safe and efficient construction of the mine under similar geological conditions.

Abstract: In this paper, which was based on a deep excavation project in Tianjin, the factors and laws of surrounding buildings and surface subsidence during the excavation were discussed through the real-time monitoring and comprehensive analysis of the subsidence of structures, underground pipelines, ground surface and some other items. The results show that the main influence scope of the excavation to surrounding areas is about 2 times the depth of the pit, and enhancing the stiffness of surrounding buildings can increase the resistant capacity against deformation, which will provide a reference for the allied projects.

Abstract: The stability of two profile, with No.Ⅲ landslide of Daping landslide group near the tunnel engineering of Sunjiaya, was respectively discussed using limit equilibrium and numerical simulation method at operation one (gravity) and two (gravity+rainstorm) in this paper. The dangerous sliding surface and corresponding safety factors was calculated by limit equilibrium method, to upper and lower parts of No.Ⅲ landslide in two different work conditions. The model of two calculation profiles was established and the dangerous sliding surface and corresponding safety factors was simulated by finite difference software of FLAC3D for upper and lower parts of No.Ⅲ landslide at two operations. Compared with limit equilibrium, FLAC3D is a simple and easy method to analyze the stability of slope.

Abstract: In order to solve the question of excess or under excavation, poorly forming around the lane, low rate of excavation caused by less drilling, arbitrarily drilling, non-standard charging, unreasonable initiation network in the construction process of half coal rock lane in Liu-wan mine. According to coal and rock conditions at the scene and through theoretical calculations and engineering analogy, made a scientific and rational borehole layout and correct initiation network, strengthened temporary support and changed operation modes. The driving rate of the single circulation was improved from 1.6m to max.2.75m. The utilization rate of the blasting boreholes was improved from 89% to previous 94.7%. The unit consumption of explosives was significantly reduced from the original 1.24kg/m3 minimum to 0.74 kg/m3.Thus the profile shape results would be good and the driving speed could be highly increased. Research results will be the same geological conditions for excavating to provide reference.

Abstract: The interfacial characteristic of reinforcement plays a significant role in reinforced engineering, and stress history is one of the key factors affecting the interfacial characteristics. By using the comprehensive geosynthesis test apparatus, a series of pull-out tests were carried out by using reinforced soil composed of silt clay and biaxial polypropylene geogrid. Base on the results of the tests and their curve between shear force and displacement, the impact of stress history on the interfacial characteristics of reinforced soil was explicitly discussed in both qualitative and quantitative manner. It is revealed that the soil’s stress history has great impact on the interfacial parameter of c (cohesive force) and  (internal frictions angle )of the reinforcement; the interfacial parameter of c and  in silty clay is increased by 12.10% and 8.56% respectively when the OCR (over consolidation ratio) increase from 1 to 2; and methods like increasing the thickness of cover soil or increasing the times of rolling to form over-consolidation can reach more higher shear strength in specified project. The results of this research should be a guide to the test, design and construction of reinforced silty clay engineering.