Experimental study of the temperature influence on mode Ⅰ fracture toughness of sandstone specimens with different porosities
The mechanical properties of hot rock are important basis for rock stability analysis and sup-port design of deep rock projects such as underground gasification of coal.In order to reveal the evolu-tion of fracture behavior of rock after high temperature,a series of tests on sandstone specimens with two porosities after different high temperatures(25-800 ℃)were carried out.Digital image processing tech-niques were used to analyze the distribution characteristics of thermal cracking,and calculate the microc-rack area ratio.Three-point bending tests were performed on semicircular bend sandstone specimens after high temperature treatment.Based on the test results,the effects of high temperature on load-displace-ment curves,mode Ⅰ fracture toughness and failure modes of sandstone specimens were analyzed.The results show that:the microcrack area ratio tends to decrease first and then increase with increasing tem-perature,and the microcrack area ratio of Group C sandstone with higher porosity is higher than that of Group A sandstone with lower porosity.The mode Ⅰ fracture toughness of Group A sandstone is higher than that of Group C sandstone under the same testing temperature.As the temperature increases,the mode Ⅰ fracture toughness of sandstone specimens first increase and then decrease.The threshold tem-peratures of the two groups of sandstones are 200 ℃ and 400 ℃,respectively.The crack initiated from the prefabricated notch tip under three-point bending leads to the failure of sandstone specimens.The higher the temperature,the more obvious the degree of fracture of the sandstone specimens.
rock mechanicshigh temperature treatmentmode Ⅰ fracture toughnessmicrostructureimage processing
万方数据
维普
