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In order to study the effect of the replacement rate of recycled coarse aggregate, length-diameter ratio and diameter-thickness ratio on the axial compressive bearing capacity of middle long columns of recycled aggregate concrete with ferronickel slag filled steel tubes (RACFNSFST), the monotonic loading tests were carried out on eight RACFNSFST under axial compression. By comparing the calculation method of axial compressive capacity recommended by the domestic and foreign common concrete-filled steel tube codes, the prediction formula of axial compressive capacity is fitted by regression and compared with the test results. The results show that local buckling occurs at both ends of the medium and long column, which is the failure mode of material, and the long column is the failure mode of whole instability. The medium and long columns with the same reclaimed coarse aggregate substitution rate and section size have better bearing capacity and slower deflection growth than that of the long columns. With the increase of diameter-thickness ratio, the bearing capacity and ductility are reduced, and the hoop effect of steel tube on recycled concrete is obvious. The fitting formula is simple and practical, and it is in good agreement with the measured value. [ABSTRACT FROM AUTHOR]

In order to explore the effect of gas explosion on the refuge chamber of coal mine, this paper carried out a numerical simulation on the process of gas explosion under the closed and open condition respectively. The physical model of the refuge chamber was established by means of applying the software of ICEM, and then Fluent software was used to carry out the numerical simulation on the pressure and temperature variation of gas explosion under different boundaries. In addition, The Origin software was used to carry out the curve fitting of the pressure as well as the temperature variation during the process of the gas explosion. The results show that under the sealing condition, the refuge chamber need withstand the high pressure of 0.61 MPa and the high temperature of 2269 K; under the condition of opening, the refuge chamber only need withstand the overpressure of 12.39 KPa and the high temperature of 1773 K respectively. Considering comprehensively the explosion overpressure and the high temperature, the position of the refuge chamber should be far away from the dead end roadway. [ABSTRACT FROM AUTHOR]