Abstract
Various tests including the longitudinal wave velocity tests and uniaxial compression tests have been conducted to evaluate the impact of cooling methods (including natural cooling, water cooling, and cooling by liquid carbon dioxide) on mechanical properties of sandstone under the natural status and high temperature. The acoustic emission signals were also monitored during the tests. According to the tests conducted, the sandstone sample density attenuation rate and the longitudinal wave velocity attenuation rate are higher than those of the specimen under natural status while the uniaxial compressive strength and Young’s modulus are lower. Comparing with the sandstone under the natural status, the compression sections of the stress‐strain curves of the high‐temperature sandstone samples treated by three cooling methods are longer with lower strain peak values. The order of the acoustic emission is revealed as follows: the sample cooled by liquid carbon dioxide < the sample cooled by water < sample cooled naturally < the sample under natural status, which suggests that the rapid cooling (cooled by liquid carbon dioxide) produces the severest damage on the sample, followed by the water cooling and natural cooling methods. In addition, the relationship between the sample strength weakening coefficient and the cooling rate is defined based on the statistical data of the cooling time of the high‐temperature specimen under the three cooling methods.
Highlights
Since the 21st century, the rapid economic development of various countries has raised higher demands to the resource, energy, and space, resulting in outstanding problems such as environmental pollution on the ground, resource shortages, and traffic congestion, which poses as a serious threat to the social health and sustainable development
Fire is one of the common disasters troubling the underground space. e high temperature and cooling effect produced during the control of fire accidents tend to modify the physical and mechanical properties of underground engineering rock mass, jeopardizing the stability and service life of underground facilities
E changes to the density attenuation rate and the longitudinal wave velocity attenuation rate responding to various cooling rates are presented in Figure 6. e cooling rate of the heated rock is a calculated parameter obtained by dividing the temperature decrease by the cooling time. e surface temperature of the specimen was measured by the infrared thermometer continuously until the specimen was cooled to 40°C ± 5°C
Summary
Since the 21st century, the rapid economic development of various countries has raised higher demands to the resource, energy, and space, resulting in outstanding problems such as environmental pollution on the ground, resource shortages, and traffic congestion, which poses as a serious threat to the social health and sustainable development. Various fire extinguishing methods produce different cooling rates, resulting in various levels of destructive effect on the high-temperature surrounding rock. Erefore, conducting research studies to evaluate the impact of different cooling methods on the mechanical properties of underground engineering rock mass after high temperature becomes necessary. In terms of the water cooling method, some scholars [15,16,17,18] analyzed the mechanical properties of high-temperature granite, marble, limestone, and sandstone after the water cooling, including the analysis of changes in uniaxial compressive strength, tensile strength, and Young’s modulus. Uniaxial compression strengths were tested with the cooling rate as the variable to explore the impact of cooling methods on mechanical properties of sandstone under high temperature.
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