Effect of Heat Treatment on Dynamic Tensile Strength and Damage Behavior of Medium-Fine-Grained Huashan Granite

Abstract

In order to investigate the dynamic behavior of medium-fine-grained Huashan granite treated by different temperatures, the splitting tests on the granite specimens are carried out using an improved split Hopkinson pressure bar (SHPB). The dynamic force equilibrium condition in the specimen is basically satisfied. The results show that with increasing treatment temperature, the ultrasonic P-wave velocity decreases, while thermal damage accordingly increases. The damage evolution follows the logistic curve model. For a temperature at or below 500°C, all the specimens break diametrically into two halves at relatively low impact velocities. As the impact velocity rises, the triangular crushed zones are observed at the two loading ends of the specimen. When the temperature exceeds 500°C, the damage of the specimen becomes severe, and even completely pulverized under high impact velocity. There are good correlations between the splitting strength and the treatment temperature, the ultrasonic P-wave velocity as well as the thermal damage. In addition, the splitting strength is slightly abnormal at 100°C, namely the strength becomes lower than that at room temperature with increasing impact velocity. Overall, the decay of the splitting strength with thermal damage for the treatment temperatures over 100°C accords with the power function. Moreover, the splitting strength of specimen is sensitive to strain rate at high temperature, but the increasing rates are different under different ranges of temperature.

Experimental and Theoretical Investigations of Hard Rocks at High Temperature: Applications in Civil Engineering

“…Determining the velocity of propagation of elastic waves (acoustic waves) through the material before and after heating is an effective tool for assessing changes in its properties depending on the temperature. e results of a large number of researchers have shown that the propagation velocity of these waves in rocks depends on the mineral composition, density, porosity, microcracks, temperature, and especially the applied pressure [19,42,59,86,87].…”

“…Damage of material is a concept that is increasingly explored and characterizes the state of degradation of this material. In rock engineering, several authors have already expressed their opinions [15,19,22,23,51,65,101,102,[111][112][113][114]. From Figure 10, it can be seen that between 300°C and 500°C, the damage of most rocks is increased continuously [115,116].…”

“…Several literature research studies also underlined the creation of microcracks by heating rate ranged between 5°C/ min and 50°C/min and concluded that it plays a significant role in the mechanical properties of the rocks [17][18][19]. As this velocity increased, the chemical structure was modified and the stiffness of rock increased.…”

Experimental Study on Dynamic Mechanical Properties and Energy Evolution Characteristics of Limestone Specimens Subjected to High Temperature

“…Rock engineering safety problem induced by high temperature had become an important topic in rock mechanics research [1][2][3]. High-temperature rock mechanical behavior was different from normal temperature, and its physical and mechanical properties were closely related to the temperature; hence, studying the mechanical behavior of rock after high temperature had important theoretical and engineering significance [4][5][6].…”

Study on the dynamic characteristics of rock surrounding a wellbore in energy storage areas during deep geothermal energy mining

“…Researchers have performed many studies on the unique mechanical conditions that rocks experience during the production of geothermal energy. It was found that the dynamic tensile failure strain of rocks increased with increasing temperature [ 10 , 11 ], and the dynamic tensile strength first increased and then decreased by using Brazilian discs to perform dynamic splitting tests of high-temperature rocks [ 12 , 13 ]. Some researchers also carried out studies on the rock surrounding wellbores under a high static load, and it was found that the dynamic tensile strength of the rock under a high static load was far greater than the tensile strength under a static load, and the failure characteristics of tensile strength mentioned above were generally consistent [ 14 , 15 ].…”