Abstract
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.
Highlights
With the rapid development of economy, society, and mining technology, the huge resource consumption has gradually depleted the shallow earth’s resources
The deformation of sandstone decreased from 25% to 20%; deformation of sandy mudstone decreased from 20% to 12.5% and deformation of mudstone decreased from 15% to 14.5%
(iv) When the temperature is lower than 40°C, the yield stage of the three types of soft rocks is shorter. e yield stage becomes more and more obvious when the temperature is higher than 40°C
Summary
With the rapid development of economy, society, and mining technology, the huge resource consumption has gradually depleted the shallow earth’s resources. Literature retrieval and analysis show that the research on safe production in deep mines has achieved certain results, mainly in two aspects: the stress of the surrounding rock in the high temperature (>100°C) range [8] and the mechanical properties of hard rock masses of the study. It can be concluded that the above research studies focus on the mechanical properties of brittle, dense, homogeneous, and isotropic rock mass (such as marble, sandstone, and limestone.) under ultrahigh temperature (>100°C) These studies provide a basis for the safety problems caused by the high-speed development of underground space engineering, there is a lack of research on the mechanical properties of coal measure sedimentary soft rocks such as sandstone, mudstone, and sandy mudstone, which are commonly found in mine lithology and affected by mine high temperature. In view of this, based on the research results of Zha et al [26, 27], this paper carried out a contrastive analysis of uniaxial mechanical properties of sandstone, sandy mudstone, and mudstone at the temperature of 25∼55°C and constructed a constitutive model of thermal damage of sedimentary soft rock
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