In order to study the difference in thermomechanical properties of soft sedimentary rocks of different coal measures, three types of soft sedimentary rocks, sandstone, sandy mudstone, and mudstone, which are common in deep mines, are tested using the RMT-150B rock mechanics test system and GD-65/150. Uniaxial compression experiments were conducted on three kinds of soft rock-cement mixed specimens at 25°C~55°C multistage temperature in an environmental chamber. The difference of important parameters such as stress-strain curve, peak stress, and elastic modulus was analyzed and compared. The results show that (i) in the test temperature range, the stress-strain curves of the three types of soft rocks at different temperatures are roughly divided into four stages: compaction, elasticity, yield, and failure. The proportion of deformation in the compaction stage to the total deformation decreases gradually with the increase of temperature. (ii) When the temperature is lower than 40°C, the yield stage is shorter, and the peak stress and elastic modulus of the three types of soft rocks decrease significantly with the increase of temperature. (iii) Above 40°C, the decreasing trend of peak stress and elastic modulus curve decreases, and the yield stage becomes more and more obvious. The decreasing rate of elastic modulus of sandstone is 0.041 GPa/°C; the decreasing rate of peak stress is 0.193 MPa/°C, the decreasing rate of sandy mudstone is 0.022 GPa/°C and 0.124 MPa/°C, and the decreasing rate of mudstone is 0.020 GPa/°C and 0.051 MPa/°C. (iv) The rationality of the established thermal damage constitutive model of sedimentary soft rock was verified.
In Pingxiang mining area of Jiangxi Province, a large amount of non-spontaneous combustion coal gangue is piled up into mountains, which not only occupies the land, but also seriously pollutes the ecological environment. In order to solve this problem and improve the utilization rate of coal gangue, the study of coal gangue without spontaneous combustion in Pingxiang mining area was carried out, and the differences of chemical composition, physical characteristics and thermal activation characteristics of coal gangue were analyzed. On this basis, the coal gangue was used as coarse aggregate instead of some natural stones, and the influence of different temperatures on the compressive properties of coal gangue aggregate concrete was studied. The results show that the compressive strength of gangue concrete is lower than that of ordinary concrete at room temperature. At high temperature, under the influence of secondary hydration of cement and thermal activation of gangue, the compressive strength of concrete test blocks in each group presents an upward trend before 400°C, and reaches its maximum strength at 400°C, among which the mechanical strength of concrete with 30% gangue coarse aggregate is the best. This study provides a basis for the resource utilization of coal gangue in Pingxiang.
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