温度和应力循环作用下花岗岩力学特性变化规律试验研究

采用多功能岩石高温三轴试验机,对花岗岩试件进行温度上限为100℃～600℃、应力上限分别为各温度下70%和85%单轴抗压强度的温度和应力循环试验,揭示温度和应力循环过程中花岗岩力学特性的变化规律,研究表明:(1)随循环次数增加,花岗岩弹性模量逐渐增大,每次循环加载的上限应变总体呈减小趋势,与应力上限为70%单轴抗压强度相比,应力上限为85%单轴抗压强度时上限应变的降低程度更大;(2)除600℃外,试件经温度和应力循环作用后的单轴抗压强度都大于对应实时温度下的强度值,其中循环温度上限为300℃时,其强度值增幅最大,在循环应力上限为70%与85%抗压强度条件下,增幅分别达到57.1%和50.9%;(3)经温度和应力循环后,花岗岩试件的强度产生明显变化,而峰值应变与实时温度下的峰值应变相差不大,说明从变形条件研究岩石的稳定性比强度条件研究岩石的稳定性更符合试验规律。研究结果对受温度和应力循环作用的深部岩石工程的稳定性研究有一定的借鉴价值。

Experimental study on mechanical properties of granite subjected to temperature and stress cycles

The uniaxial compression test of granite specimens under temperature and stress cycles was carried out to reveal the mechanical properties of granite subjected to temperature and stress cycles. The results show that,with increasing the cycle number,the Young’s modulus of the granite increases gradually while the strain corresponding to the upper stress of the samples decreases. The decrease amplitude of the upper limit strain at the upper limit stress of 85% uniaxial compressive strength is greater than that at 70% uniaxial compressive strength. Except for 600 ℃,the uniaxial compressive strength of the samples after temperature and stress cycles is greater than that at real-time temperature. Especially for 300 ℃,the strength increase rates at the upper cycle stresses corresponding to 70% and 85% uniaxial compressive strength reach 57.1% and 50.9% respectively. After temperature and stress cycles,the strength of the granite specimen changes significantly while the peak strain almost keeps invariable,which shows that studying the stability of rock from deformation rather than strength is more consistent with the actual situation. The results can provide reference to study the stability of rock engineering under the cyclic action of temperature and stress.