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.