高温后砂岩单轴压缩加载速率效应的试验研究

Experimental investigation on loading rate effect of sandstone after high temperature under uniaxial compression

温度是影响岩石材料物理力学性质的重要因素,为考察温度对砂岩加载速率效应的影响规律,对25℃~800℃之间6种温度水平后的砂岩试样分别进行不同加载速率下的单轴压缩试验。试验结果表明:①高温后砂岩的物理性质出现一定的劣化,由25℃升高至800℃,密度和纵波波速分别减小了5.89%和73.72%;②随着温度的升高,砂岩峰值强度和弹性模量逐渐减小,峰值应变逐渐增大,而峰值强度随温度的变化过程受加载速率的影响较大;③高温后砂岩的峰值强度和峰值应变具有明显的加载速率效应,且服从正线性关系,相关性参数A表征了材料受加载速率影响的显著程度,随着温度的升高参数A呈现先减小后又增大的趋势;④随着温度和加载速率的增大,砂岩破坏形态由拉剪混合破坏逐步转化为单一斜剪破坏,破坏程度愈渐剧烈,分形维数也逐渐增大。

The temperature is a very important factor affecting the physical and mechanical properties of rock. Uniaxial compression tests on sandstone after high temperature with six temperature levels between 25℃ to 800℃ under different loading rates are conducted to investigate the influence of temperature on loading rate effect. The results show that the physical properties of sandstone after high temperature appear to have a certain degradation, and that the density and longitudinal wave velocity respectively decrease by 5.89% and 73.72% with temperature rising from 25℃to 800℃. With the increase of the temperature, the peak strength and elastic modulus decrease little by little, but the peak strain increases gradually, and the evolutionary process of the peak strength along with the temperature is strongly influenced by the loading rate. The peak strength and peak strain of sandstone after high temperature have an obvious loading rate effect, and they obey the positive linear relationship. The correlation parameter A characterizes the impact degree by loading rate, and with the increase of temperature, parameter A first decreases and then increases. The failure mode of sandstone transforms from mixing failure of tensile and shear gradually into a single shear failure with the increase of the temperature and loading rate, the damage degree becomes increasingly more serious, and the fractal dimension also increases gradually.