温度对盐岩疲劳特性影响的试验研究

EXPERIMENTAL STUDY OF TEMPERATURE EFFECT ON FATIGUE PROPERTY OF SALT ROCK

对不同温度下的盐岩试件进行单轴压缩试验,发现盐岩单轴抗压强度随着温度的升高明显下降,峰值应变却随着温度的升高而逐渐增大。根据不同温度下盐岩的单轴抗压强度选取合适的上、下限应力值,对各温度条件下盐岩试件进行循环荷载试验,发现:盐岩在相同应力比循环荷载作用下,疲劳寿命随着温度的升高而增加;不同温度下盐岩的疲劳损伤发展模式都包括减速损伤阶段、匀速损伤阶段和加速损伤阶段;随着温度的升高匀速疲劳损伤阶段所占的比例增加;与轴向应变曲线相比,体积应变的3个损伤阶段更加明显。最后应用弹塑性材料损伤分析公式,对盐岩的疲劳损伤进行分析,发现盐岩损伤发展模式与盐岩试件的体积应变发展模式较为接近,因此选取体积应变来描述盐岩的疲劳损伤较为合理。

By uniaxial tests on salt rock specimens under different temperatures, it is shown that the unlaxlal compressive strength of salt rock drops significantly and the peak strain increases gradually with the increase of temperature. Through the cyclic loading test under different temperatures, in which the upper and lower limit stresses are chosen according to the uniaxial compressive strength under different temperatures, it is found that： （1） The fatigue life of salt rock under the same stress ratio becomes longer as the temperature rises. （2） The fatigue damage development mode of salt rock under different temperatures all includes three stages： slow damage stage, uniform damage stage and accelerated damage stage. （3） The proportion of uniform damage stage increases as the temperature becomes higher. （4） The curve of volumetric strain shows the three stages more obviously than the axial strain curve. Finally, the fatigue damage of salt rock is analyzed by using the analytical formulas for elastoplastic material damage. It is indicated that the development mode of salt rock fatigue damage is matched with that of the volumetric strain. Therefore, the volumetric strain is more appropriate for describing the fatigue damage of salt rock.