## 5 Conclusions  
In this study, a split Hopkinson pressure bar (SHPB) test system with real-time temperature control was developed, and dynamic tests on limestone taken from deep coal mines were carried out in real-time temperatures from 25 to 800 \({}^{\circ}\)C. The XRD, SEM, and EDS tests were conducted to investigate the fracture mechanism of the limestone specimen at real-time temperatures. The main conclusions are as follows:  
1. Under the coupling effect of real-time temperature and impact loading, the dynamic stress-strain curve of the limestone specimen has no evident compaction stage, while the strain rate demonstrates a nearly linear correlation with the impact velocity across  
Figure 15: Variation in the microfracture patterns under different strain rates and at a temperature of 800 \({}^{\circ}\)C.  
different temperatures. As the temperature increases, the dynamic compressive strength of the limestone specimen decreases linearly at a rate of 0.15 MPa/\({}^{\circ}\)C within the strain rate interval of 40-60 s\({}^{-1}\), 60-80 s\({}^{-1}\), and 80-100 s\({}^{-1}\). Additionally, a negative exponential nonlinear relationship is established to describe the variation of elastic modulus with temperature.
2. The dynamic compressive strength increases linearly with strain rate at different temperature ranges of 25-800 \({}^{\circ}\)C. The temperature sensitivity coefficient \(\eta\) is defined to quantify the influence of temperature on the variation of dynamic compressive strength with strain rate, and a quantitative relationship is established accordingly. Moreover, the correlation between dynamic elastic modulus and strain rate can be characterized by a Boltzmann function. The macroscopic fracture characteristics of the limestone specimen under real-time temperature and the impact load are also obtained.
3. The real-time high temperature leads to a decrease in dolomite content and an increase in calcite content due to the thermal decomposition of dolomite, resulting in a significant reduction in the mechanical properties of the limestone specimen. With the increasing real-time temperature, the number of micro-cracks on the fracture surface of the specimen under impact loading is greater, the crack width is wider, and the breakage degree is higher. As a result, the fracture characteristics of the calcite mineral components change from brittle failure to brittle-ductility failure. The action mechanism of real-time high temperatures on the physical and chemical properties of limestone can be categorized into three characteristics: physical reinforcement, physical degradation, and physical and chemical deterioration.  
[PERSON] conceived and designed the research. Material preparation was performed by [PERSON] and P.W. Testing, data collection, and analysis were performed by [PERSON], [PERSON], [PERSON], S.G. and F.Z. The first draft of the manuscript was written by [PERSON], and all authors commented on previous versions of the manuscript. All authors have read and agreed to the published version of the manuscript.  
This work was supported by the National Natural Science Foundation of China (52074240, 52274140, and 52304102), Excellent Innovation Team Project of Universities in Jiangsu Province, China (Engineering Structural Safety under Complex Environmental), State Key Laboratory for Geomechanics and Deep Underground Engineering, China University of Mining and Technology (SKLGDUEK2212).  
Not applicable.  
Some or all data, models, or codes that support the findings of this study are available from the corresponding author upon reasonable request.  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.