循环单轴应力和循环温度作用下玄武岩力学性质初探

对玄武岩在循环单轴应力–温度作用下的力学性质进行初步的试验研究。开展应力上限为80%和65%单轴抗压强度、温度上限为60℃和90℃的循环单轴应力–温度试验以及循环后的单轴压缩试验。试验结果表明:循环应力和循环温度作用具有"叠加"效应;循环应力上限为80%单轴抗压强度时,玄武岩随循环次数增加逐渐损伤,在循环中破坏;应力上限65%抗压强度且温度上限60℃时,玄武岩随循环次数增加逐渐硬化,在循环中不会发生破坏;损伤岩样峰值应变经历初始阶段、等速阶段和加速阶段,残余应变具有较大波动性;损伤岩样峰值割线模量先迅速降低,后缓慢降低,在临近破坏时急剧减小,应力上限大时峰值割线模量的降低程度大;应力上限相同,温度上限大的损伤岩样破坏循环数小;硬化岩样峰值应变和残余应变随循环次数增加而减小,峰值割线模量、割线弹性模量和卸载模量随循环次数增加而增大,温度上限大时岩样模量增加幅度小;硬化岩样受循环作用后,抗压强度较初始强度提高;岩石破坏时峰值应力与峰值割线模量定义的损伤因子线性相关程度高。

Preliminary study on mechanical property of basalt subjected to cyclic uniaxial stress and cyclic temperature

The mechanical property of basalt subjected to cyclic uniaxial stress and cyclic temperature is preliminarily studied through laboratory tests. Cyclic uniaxial stress-temperature tests are conducted during which stress upper limit is 80% or 65% of the uniaxial compressive strength and peak temperature is 60℃ or 90℃. Uniaxial compression tests after cycling are also performed. The results exhibit superposition of the effects of cyclic temperature and cyclic stress. The basalt specimens are gradually damaged with the increase in cycle number and fail in the cycles when the maximum stress is 80% of the uniaxial compressive strength. However, the specimens are gradually hardened and do not fail in the cycles when the maximum stress is 65% of the uniaxial compressive strength and the highest temperature is 60℃. The peak strain of a damaged specimen undergoes initial acceleration, steady and acceleration stages, while the residual strains fluctuate. The peak secant modulus of the damaged specimen decreases rapidly in the initial cycles, and then it decreases at a relatively low rate during most of the cycles, and drops sharply when the failure occurs. A higher stress upper limit results in more variations in the peak secant modulus. Failure cycle number is smaller at a larger temperature upper limit. The peak and residual strains of a hardened specimen decrease with the increase in the cycle number. However, the peak secant, secant-elastic and unloading moduli have opposite trends. Higher temperature results in smaller modulus variations. The uniaxial compressive strengths of the hardened specimens increase after stress-temperature cycling. The peak stress has a high linear degree of correlation with the damage factor defined by the peak secant modulus when the specimens fail.