高低温加载对大理岩力学特性影响的试验研究

许多工程（如采矿、隧道掘进、地热开采等）都涉及到岩石损伤及破碎问题．传统的岩石损伤破碎技术，如爆破法、水射流法、机械掘进法等均面临着一系列问题，利用岩石的热损伤性质辅助机械破岩有望实现安全、高效破岩的目的．大理岩是一种典型的硬岩，常见许多工程之中，因此本文以大理岩为研究对象，首先将均质性较好的大理岩试样加热至不同温度(20~1000 °C)后放入液氮中进行急速冷处理，然后对其进行了系列的物理力学性质测试．试验结果表明：处理后密度、纵波波速、抗拉强度、单轴抗压强度(UCS)和弹性模量整体上都随温度的上升而下降；当加热温度在100 °C之前，大理岩表现出一定的热硬化现象，即随着温度升高，其UCS、纵波波速以及弹性变形模量均增大；UCS变化的阈值温度为400 °C左右，一旦温度超过400 °C，UCS迅速下降，其速率达到了9 MPa/100 °C，当温度超过500 °C弹性模量迅速下降，其速率达到7.00 GPa/100 °C，表明岩样抵抗变形能力减弱．整体上，热加载降低了大理岩的脆性，使其在单轴作用下的破坏模式由脆性破坏逐渐转化为弹塑性破坏．

Experimental Study on the Influence of Heating and Rapid Cooling Treatment on the Mechanical Properties of Marble

Many projects (such as mining, tunneling, geothermal mining, etc.) involve rock damage and fragmentation problems. Traditional rock damage technologies, such as blasting, water jet method, and mechanical tunneling, all face a series of problems. Using the thermal damage properties of rocks to assist mechanical rock breaking is expected to achieve the purpose of safe and efficient rock breaking. Marble is a typical hard rock, which is commonly used in many projects. Therefore, this article takes marble as the research object. First, the marble sample with good homogeneity is heated to different temperatures (20 ~ 1000 °C) followed by liquid nitrogen cooling treatment. Then a series of physical and mechanical tests were conducted on the treated samples. The test results show that the density, P-wave velocity, tensile strength, uniaxial compressive strength (UCS), and modulus of elasticity generally decrease with temperature after treatment; when the heating temperature is below 100 °C, marble shows a certain thermal hardening phenomenon, that is, as the temperature increases, its UCS, P-wave velocity, and elastic deformation modulus all increase. The threshold temperature for UCS change is about 400 °C. Once the temperature exceeds 400 °C, UCS decreases rapidly with a rate as high as 9 MPa/100 °C. When the temperature exceeded 500 °C, the elastic modulus rapidly decreased at a rate of 7.00 GPa/100 °C, indicating that the rock specimen's resistance to deformation was weakened. Overall, the thermal loading reduces the brittleness of rock, which transfers the failure mode gradually from brittle failure to elastic-plastic failure under uniaxial compression.