Applied Mechanics and Materials Vols. 170-173

Abstract: Gu Bei coal mine deep shaft freezing pressure of calcareous clay dynamic monitoring showed that the freezing pressure of the calcareous clay fastest grow in the first 2 weeks after the sidewall concrete pouring , freezing pressure has obvious direction . Analysis showed that the layer of freezing pressure is mainly calcareous clay layer deformation pressure, size and the temperature of well has a positive correlation. Maximum freezing pressure of the deep calcareous clay layer approximate the permanent formation pressure values and the maximum frost heave force determined by the frost heave experiments in indoor closed systems ,the average freezing pressure with depth variation of the exponential function can be used to good description.

Abstract: Based on the mining conditions of Muchengjian Coal Mine in Beijing, the evolution process of the overburden fractured zone was simulated by the distinct element software UDEC. The simulation results show that with the increase of the mining area, fractured expansion space continues to increase upward and is arched distribution. The fracture changes significantly during primary mining and develops slowly latterly. It reaches steadily 8 times thickness of mining coal eventually. The author uses drilling camera detection technology for detecting destruction of overburden and the development situation of the fracture. Based on the results of detection, overburden fracture can be divided into mild fracture zone, moderate fracture zone, and severe fracture zone according to the fracture degree. The fracture develops unevenly in boreholes and shows that the fractured zone and complete zone appeared alternately. The simulation results have a good agreement with the measured data. And the height of stress arch is suit for the upper limit of fracture development, which can be provided guidance for coal mining in the similar conditions.

Abstract: As the complexity of unsaturated soil theory, and it must have a long test period when we study the unsaturated soils, so the conventional design analysis software does not provide such analysis, so we can imagine that such a slope stability analysis does not accurately reflect the actual state of the slope. Based on the known soil moisture content，this paper use the soil water characteristic curve and strength theory of unsaturated soil to calculate the strength reduction parameters of soil which can calculate the stability of the soil slope when using the common calculation method. It is noticeable that this method can be extended and applied if we establish regional databases for this simple method, and these databases can improve the accuracy of the calculation of slope stability.

Abstract: This paper firstly expounds the scope and principle of riprapping for sludge extrusion, and then details of quality control standard of the construction technology and process are described according to the engineering practice. The points of subsidence, surrounding upheaval, deep horizontal displacement, and pore water pressure are also monitored respectively set in hydraulic fill mud area. The monitoring data are analyzed for conclusion to explore the feasibility and existing problems of riprapping for sludge extrusion in this experiment.

Abstract: This article presents a case history of piezocone penetration test (CPTU) of soft deposit in Shanghai. In Shanghai, stratigraphy for soft deposit is mainly obtained by the laboratory test with borehole samples. The stratigraphy identified by CPTU was developed and improved in recent decades. The analysis is carried out with the field data at test site of Yan’an Road Tunnel in Shanghai. The stratigraphy chart proposed by Robertson (1990) is employed to identify soil layer. The results show that the Robertson charts (1990) is suitable to identify the stratigraphy of the soft deposit in Shanghai. However, there are some discrepancies of the results from Robertson charts (1990) and the norm method. Discussion on the reasons of these discrepancies is conducted.

Abstract: With ANSYS/LS-DYNA dynamic analyzing method, the 3-D finite element model of testing segregation piles with low strain method is got. By analyzing reflective oscillogram of the segregation layer with the same thickness but different strength, the method to analyze the strength of the segregation layer is got. By comparing the reflective oscillogram of the concrete with the same strength but different thickness of the segregation layer, the method to test segregation thickness is formed. The experiment states that when the pile defect is qualitatively validated as segregation by accurately analyzing the amplitude of the stress wave of the segregation part and the amplitude of the reflective wave of the bottom pile, including the time corresponding to the amplitude. The level of the defect of the segregation layer can be judged quantitatively in a much smaller error range.

Abstract: Evaluation of slope stability is a complex system problem of uncertainty. A new model for slope stability evaluation was established based on the Attribute Recognition Model (ARM) and the Projection Pursuit (PP) optimized by the Particle Swarm Optimization (PSO), which was named as Attribute Recognition Model based on Projection Pursuit Weight (ARM-PP). The attribute measurement of single index was computed through constructing the attribute measurement functions, and the synthetic attribute measurement was calculated by the weight of PP optimized by PSO. Confidence criterion was used to recognize the slope stability. The attribute mathematical theory could successfully resolve the comprehensive evaluation problem with a number of fuzzy attribute. Furthermore, ARM-PP adopted the PP to determine weight, avoiding the subjectivity and randomicity, and ensuring objectivity and accuracy of the evaluation. Case study showed that ARM-PP was feasible and precise in slope stability evaluation.

Abstract: Common mining methods for thick coal seams or extremely thick coal seams has slice mining top coal caving mining, greater height mining, and surface mining. From the perspective of economic and technological mining method, the choice of methods should be fully taken into account the technical, economic, quality of operating personnel, equipment, geological conditions. It allows priority to open-pit mining, and then according to the thickness, coal quality, coal other factors to select the top coal caving or mining of high extraction methods which can achieve the economic, security, and efficient purposes. Conversely, if the method is poor choice, it will certainly lead to economic and time losses.

Abstract: As the main method of the foundation pile low strain dynamic test, the reflected wave method has been widely recognized in engineering after years of research and application. Among the many elements of affecting quality of pile foundation, the influence of excitation frequency on pile inspection is research focuses in this paper. This paper analyzes and summarizes the rules of the effect the exciting force produces in low strain integrity testing by using laboratory simulation experiment.

Abstract: With the static load tests of seven piles under the clinic building of the first people hospital in Chang-De city, the character and dimension effect of long spiral mud-jack bored pile’s pressure~settlement curve is analyzed.The result of study shows that the curve may be simulated by Duncan-Chang model so as to obtain exact and alone ultimate load, the increasing of pile diameter can increase the capacity and reduce the settlement more than the increasing of pile length. In order to use the technique widely, the result of the paper can offer the reference in Dong-Ting area.