The effect of high temperature on engineering properties of rocks has recently become an important topic for geotechnical engineering applications due to the development in geothermal energy extraction, underground coal gasification, disposal of nuclear waste and deep mining applications. This study aims to investigate the engineering properties of four rocks heated at high temperatures and to identify the corresponding mineralogical changes. Two types of sandstone (Beaudesert sandstone and Jimboomba sandstone), basalt and argillite were subjected to a range of temperatures from 25 to 800 °C and their properties such as porosity and point load index were studied through a series of laboratory experiments. The physical and mineralogical alteration of the heated rock specimens were also investigated to better understand the thermally induced processes that occurred in each rock type using the X-Ray Diffraction, Thermogravimetry (TG), Differential Scanning Calorimetry (DSC) and Derivative Thermogravimetry (DTG) techniques. The obtained data indicated the important role of mineral composition in the thermal behaviour of the studied rocks. Noticeable changes in the mineral compositions at the threshold temperature were observed for each rock type. This behaviour was confirmed with TG/DSC/DTG analysis. This temperature-related process resulted in the formation of cracks, an increase in porosity and a decrease in strength. However, the effects of high temperatures on engineering properties were found to be different in the two sandstone types. While Beaudesert sandstone underwent significant weakening at high temperatures, only a slight change in the strength of Jimboomba sandstone was recorded. The threshold temperatures were identified as 400 °C, 400 °C, 500 °C and 300 °C, for the tested Beaudesert sandstone, Jimboomba sandstone, basalt and argillite samples, respectively. The critical temperatures (obtained using a damage coefficient) were found as 570 °C for both Beaudesert sandstone and basalt, and 440 °C for argillite. Analysis of the laboratory data revealed the difference between the threshold temperatures and the critical temperatures. It is recommended to use both threshold temperature and critical temperature parameters to provide more accurate estimations of the temperature range at which rock undergoes significant changes.

由于地热能提取，地下煤气化，核废料处理和深层开采应用的发展，高温对岩石工程特性的影响最近已成为岩土工程应用的重要课题。这项研究旨在调查在高温下加热的四种岩石的工程特性，并确定相应的矿物学变化。对两种类型的砂岩（Beaudesert砂岩和Jimboomba砂岩），玄武岩和泥晶石进行了25至800°C的温度范围测试，并通过一系列室内实验研究了它们的性质，例如孔隙率和点载荷指数。还使用X射线衍射，热重法（TG），差示扫描量热法（DSC）和导数热重法（DTG）对加热的岩石标本的物理和矿物学变化进行了研究，以更好地了解每种岩石类型中发生的热诱导过程。技术。所得数据表明矿物成分在所研究岩石的热行为中具有重要作用。对于每种岩石，在阈值温度下观察到矿物成分的显着变化。TG / DSC / DTG分析证实了这一行为。这种与温度有关的过程导致裂纹的形成，孔隙率的增加和强度的降低。然而，发现两种类型的砂岩中高温对工程性能的影响是不同的。尽管Beaudesert砂岩在高温下明显减弱，但仅记录到Jimboomba砂岩的强度略有变化。对于测试的Beaudesert砂岩，Jimboomba砂岩，玄武岩和泥晶石样品，确定的阈值温度分别为400°C，400°C，500°C和300°C。对于波德塞特砂岩和玄武岩，发现的临界温度（使用损伤系数获得）均为570°C，而对于辉石，则为440°C。对实验室数据的分析表明，阈值温度和临界温度之间存在差异。建议同时使用阈值温度和临界温度参数，以更准确地估算岩石发生重大变化的温度范围。