## 5 Conclusions  
Research has shown that thermal shock reduces the physical and mechanical properties of rocks and can even lead to rock fracture, and this finding has been applied to engineering construction. However, previous studies on thermal shock on rocks have usually only been conducted in a qualitative manner. The study conducted an experimental study on the physical and mechanical properties of limestone after thermal shock from 100 \({}^{\circ}\)C to 600 \({}^{\circ}\)C, and the following conclusions were obtained. (1) After thermal shock, the apparent color, mass, and volume of limestone changed and were mainly affected by the peak heating temperature. The apparent color of the specimen gradually changed from off-white to white with the increase in heating temperature. The mass of the specimen decreased with the increase in heating temperature, with a maximum decrease of 1.39%, and 500 \({}^{\circ}\)C was the sudden change temperature of mass loss. The volume of the specimen nonlinearly increased with the increase in heating temperature, and the maximum increase was 2.79%. (2) Thermal shock has a significant effect on the mechanical properties of limestone, and the peak temperature of heating in combination with abrupt cooling act together to deteriorate the mechanical properties of limestone. Thermal shock has a significant effect on the mechanical properties of limestone, and the heating and cooling temperatures work together to deteriorate the mechanical properties of limestone. As the heating temperature increased (cooling temperature decreased), the uniaxial compressive strength, elastic modulus, tensile strength, and cohesion of limestone decreased by 39.5%, 59.5%, 42.9%, and 43.2% (19.3%, 22.9%, 7.6% and 22.5%), respectively. Peak strain and angle of internal friction increased by 74.2% and 27%, respectively. The ductility characteristics of limestone were enhanced. (3) The mechanical parameters of limestone after thermal shock had a good exponential function correlation with the heating temperature. The empirical equations of uniaxial compressive strength, elastic modulus, and tensile strength of limestone at different cooling temperatures versus heating temperature were obtained by fitting the experimental results. (4) The differences in physical and mechanical properties of limestone after thermal shock and high temperature were compared and analyzed. It was found that the thermal shock in the course of quenching the heated specimens had a stronger deterioration effect on the physical and mechanical properties of limestone than the heating itself. The above conclusions reveal the macro-mechanical properties of limestone under the action of thermal shock. The effect of thermal shock on the physical and mechanical properties of limestone was quantitatively characterized. The complex combined effect of heating and cooling temperatures is proposed on the basis of previous studies of the effect of single factors (high or low temperature) on rock properties. This enriches the theory of high-temperature rock mechanics and provides technical support for the drilling and wellbore stability assessment of geothermal development in limestone reservoirs. Next, we will study the fine-scale fracture characteristics of rocks under thermal shock using a variety of non-destructive testing and visualization techniques. We will also combine them with the evolution of macroscopic mechanical parameters of rocks to study the interrelationship between them and further reveal the mechanism of rock rupture by thermal impact. [PERSON] performed the experimental work and wrote the manuscript. [PERSON] developed the idea of the research, supervised the research, and revised the manuscript. [PERSON] assisted with the experimental work and revised the manuscript. [PERSON] supervised the research and revised the manuscript. All authors have read and agreed to the published version of the manuscript. This research was sponsored by the General Pro-gram of National Natural Science Foundation of China (Grant no. 51874207).