Advanced Materials Research Vols. 250-253

Abstract: Taking the 2204 working face of Xinzhi Colliery in Huozhou as the background, through experiment of analog simulation, analyze the structure type of old goaf overburden rock breakage, instability activation mechanism of overburden rock and instability form and condition for stability of voussoir beam of old goaf. As the result, after mining and breakage, the rock mass structure of old goaf and overburden rock can be divided four types. This secondary rock structure has an important effect on old goaf activation. The existence form will decide the basic characteristic of old goaf activation. Through the mechanics analysis on voussoir beam of old goaf , it is obtained that instability due to sliding mainly depend upon the physical mechanics characteristic of key block and sideward rock, W/T value, and additional load of building on surface and so on. Rotational instability is related to the physical mechanics characteristic of key block and sideward rock and thick and length ratio h/l of the hanging rock

Abstract: The article makes a simulation on the external CFRP prestressed reinforced concrete continuous beams with ANSYS, the beams which had made analysis by Kiang Hwee Tan and Robert A. Tjandra. There is a little difference between the results of simulation and experimental results. It shows the reliability of simulation on concrete continuous beams with ANSYS. Then it makes a finite element analysis about parameters of the bending properties of continuous beams. It could provide relevant information about bending performance of concrete continuous beams with external CFRP prestressed tendons.

Abstract: Through a lot of rock salt dissolving characteristics tests without stress effect, rock salt dissolving model without stress effect has been studied. The variation of shape of rock salt solid surface has been controlled by rock salt dissolving process directly, and rock salt dissolving model without stress effect can be built by the process of exchange of materials in dissolved boundary layer; through rock salt dissolving characteristics test without stress effect under different concentration, the computing equation by dissolved mass per unit area and concentration and dissolving time has been obtained; depended on the result of test and rock salt dissolving model without stress effect, the value of diffusion coefficient of rock salt has been computed. The achieved results on this paper can provide a foundation for the further analyses of rock salt dissolving characteristics with stress effect.

Abstract: In this study, in order to verify wave induced buoyancy effects by wave conditions of wave height and period, experimental studies were conducted to the floating structures of pontoon type. A series of small-scale tests with various wave cases were performed to the pontoon models. Two small-scale pontoon models having different bottom details were fabricated and tested under the five different wave cases. Six hydraulic pressure gauges were attached on the bottom of pontoon models and wave induced hydraulic pressure was measured during the tests. Finally, hydraulic pressure subjected to the bottom of pontoon models were compared with each other. As the results of this study, it was found that wave induced hydraulic pressures at bottom were dependent on the wave period as well as wave height, and waffled bottom shape hardly influenced on wave induced hydraulic pressure.

Abstract: In order to improve the efficiency of the direct testing machine for rock tension experiments, a new elastic foundation of lower clamper is used to replace the original rigid one. By using this direct tension machine, the complete stress-strain tensile curve of rocks sample was obtained, and the rock mechanical property was studied with this experimental result. Basing comparing the experimental result between the indirect and direct tension experiment, the authors recommend it may obtain the mechanical parameters by direct tension test as well.

Abstract: High temperature conventional triaxial compression test of shale are carried out by the MTS815 servo-controlled testing machine, based on the experimental results, the relationships between temperature and shale peak strength, elastic modulus, Poisson's ratio, cohesion, internal friction angle are investigated. Although the experimental results are discrete comparatively, the general law is obvious. When the confining pressure imposed on shale is constant and the temperature changes form 25°C to 120°C, with the increasing of the temperature, the triaxial compression strength, shear strength gradually increase, while average elastic modulus, Poisson's ratio has a slightly decrease. The thermal stress generated by the high temperature plays a role to accommodate the deformation and the function of preventing crack propagation, thus the bearing capacity of shale samples are strengthened. But the influence of temperature on shale mechanical properties mutates when the temperature is at 80°C. Shale peak strength dramatically decreased, average elastic modulus decreased slightly, and Poisson's ratio also increased slightly, which indicated that at 80°C, different thermal expansivity of mineral particles of shale may cause cross-grain boundary thermal expansion incongruous, creating additional thermal stress, thus the sample’s bearing capacity decreased.

Abstract: More problem about the corrosion of concrete structures in subway engineering at home and abroad has been reported, people have analyzed that many factors have caused the corrosion of its concrete structure according to environmental characteristics and the location, such as the stray current and chloride ion and so on.we have reviewed the current research of the corrosion of concrete structures in subway engineering concerned on stray current and chloride ion, pointing out the direction of the study of corrosion of concrete structures in subway engineering.

Abstract: Obtained stress distribution of hammer bottom according to the analysis of horizontal and vertical red sandstone fill dry density of the hammer bottom after dynamic compaction; affirmed the stress distribution situation of the hammer bottom through comparative analysis of the test results by laboratory and field monitoring.

Abstract: The risk evaluation of environmental monitoring indexes during deep excavation was systematically investigated and applied to a real project. The risk analysis was carried out based on the collected environmental monitoring data. The potential accidents which may be caused by the abnormal environmental monitoring indexes were analyzed. The risk sources which may arouse the value variation of the environmental monitoring indexes were disclosed. The dynamic controlling measurements for the risk sources were suggested. The successful application of the dynamic method to the real project further verified its feasibility.

Abstract: Plate anchor is one of the most popular types of anchors widely used in geotechnical engineering. Reliable prediction of the ultimate uplift resistance of plate anchors requires its failure modes well understood. In this paper, an image-based deformation technique, the digital image cross-correlation (DIC), is used to measure the sand deformations around a scaled semi-circular anchor during uplifting. A series of tests have been conducted to investigate the failure modes of plate anchors in both loose and dense sand. Two distinctively different failure modes are measured by using DIC in both loose and dense sand respectively. This model study improves the understanding of the failure and development of loading capacity of uplift anchor in cohesionless soil.