低加载应变率下页岩力学特性试验研究1)

EXPERIMENTAL RESEARCH ON MECHANICS CHARACTERISTICS OF SHALE UNDER DIFFERENT LOADING STRAIN RATES1)

  • 摘要: 利用室内三轴试验获取页岩破坏的典型应力应变曲线。试验结果表明:在所设定的应变率范围内,低围压条件下(10 MPa,30 MPa),峰值强度随应变率升高呈增大的趋势;在高围压的条件下(50 MPa),页岩的应变率效应减弱甚至丧失;随着加载的应变率减小和围压增加,页岩破坏模式由脆性劈裂--剪切破坏向单一剪切破坏转变,页岩的脆性特征被弱化。通过试验结果分析,研究了应变率对页岩内部能量转化、损伤演化的影响规律,可为我国页岩气的大规模开采提供一定的指导理论与方法。

     

    Abstract: The typical stress-strain curves of shale failure are obtained by triaxial tests. The results show that in the range of strain rate tested the peak strength increases noticeably with the increase of strain rate under low confining pressure (10~MPa, 30~MPa), but it increases only mildly or even stabilizes under high confining pressure (50~MPa). The failure mode of shale evolves from brittle splitting shear failure to single shear failure when decreasing the strain rate and increasing the confining pressure, which means that the brittle characteristics of shale is weakened. The influence of strain rate on energy conversion and damage evolution in shale is also investigated, which enriches both the theory and method for large-scale exploitation of shale gas in China.

     

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