Study on physical and mechanical properties of rock under high temperature action
Baoheng Liu
College of Energy and Mining Engineering, Xi'an University of Science and Technology
Yongping Wu
College of Energy and Mining Engineering, Xi'an University of Science and Technology
DOI: https://doi.org/10.59429/pest.v8i1.13418
Keywords: high temperature; rock; physical properties; mechanical properties; thermal damage; microscopic mechanism
Abstract
To explore the influence laws and internal mechanisms of high temperature on the physical and mechanical properties of rock, and clarify the evolutionary characteristics of rock performance under different lithologies and temperature conditions, this paper takes the tight sandstone of Xujiahe Formation, shale of Longmaxi Formation in Sichuan Basin and granite of Beishan in Gansu Province as the research objects. By combining laboratory experiments with numerical simulation methods, the variation laws of physical properties (bulk density, porosity, permeability, acoustic characteristics) and mechanical properties (uniaxial compressive strength, elastic modulus, Poisson's ratio, creep characteristics) of rocks after hightemperature treatment in the range of 30℃ to 1000℃ are systematically studied. The microscopic damage mechanism of rock under high temperature is analyzed, and a disturbed state constitutive model of hightemperature rock is established. The research results show that there are differences in the high-temperature threshold of rocks with different lithologies: the threshold temperature of sandstone is about 500℃, that of shale is about 400℃, and the strengthening-weakening transition temperature of granite under shortterm heating is about 200℃. With the increase of temperature, the bulk density of rock decreases gradually, the porosity and permeability increase significantly, the acoustic parameters show a downward trend, and the mechanical strength and elastic modulus decrease overall. Long-term heating will further aggravate rock damage due to subcritical crack propagation. The damage effect of high temperature on shale is significantly higher than that on sandstone, which is mainly attributed to the combustion and pyrolysis of organic matter in shale. Confining pressure can inhibit the crack propagation of rock under high temperature and improve the long-term stability of rock mass. The research results can provide theoretical basis and technical support for practical engineering such as nuclear waste disposal, geothermal resource development, oil and gas well stimulation, and fire resistance design of underground engineering.
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