周期荷载作用下盐岩疲劳特性试验研究

Testing Study on Fatigue Deformation of Salt Rock Under Cyclic Loading

利用RMT-150C型岩石力学多功能试验机,针对盐岩进行了单、三轴周期荷载作用下的疲劳试验,研究了盐岩的破坏特征、变形特性及损伤。单轴试验结果表明,盐岩疲劳破坏终点的变形量受静态轴向应力-应变全过程曲线的控制,周期荷载的上限应力和幅值对盐岩的疲劳寿命有着显著影响;轴向应变和损伤都可以分为初始、等速和加速三个阶段;当上限应力小于单轴抗压强度的75%时,盐岩未发生明显破坏,疲劳效应明显弱化,可以认为是盐岩的门阀值为75%。盐岩的三轴疲劳试验表明:不同上限应力和幅值对疲劳寿命起关键作用;盐岩在三轴周期荷载作用下,很快完成初始变形阶段,而很长时间内处于稳定的等速变形过程,这种疲劳特性对储气库的稳定性有利。

Testing study is made on the fatigue failure and deformation mechanism of salt rock under uniaxial and triaxial compression condition with rock mechanics test equipment RMT-150C.The uniaxial testing results indicate that the fatigue failure curve is controlled by complete stress-strain curve under static loading.The deformation modulus of salt rock also can be divided into three stages： first,deformation modulus increasing;second,deformation modulus is in slightly decreasing trend;third,deformation modulus decreasing sharply.When the maximum loading is above 75% of compressive strength of salt rock,the fatigue failure will be taken place.The triaxial testing results indicate that fatigue life is decided by the maximum and average cyclic load.On the triaxial cyclic load,the first phase of deformation modulus increasing will finish at soon and the second phase（deformation modulus is in slightly decreasing trend） will be prolonged.The second phase of fatigue failure is a good factor for the stability of gas storage.