岩石剪切亚临界裂纹扩展长度的研究

Sub-critical crack growth length of shear (Mode Ⅱ) fracture of rock

采用剪切盒实验获得岩石平面剪切(II型)断裂,利用Drucker-Prager强度准则推导了岩石的剪切亚临界裂纹扩展长度公式,并通过岩样裂纹尖端断口的扫描电镜实验加以验证。结果表明:利用Drucker-Prager强度准则建立的岩石剪切亚临界裂纹扩展长度计算公式具有形式简单、参数容易确定等优点;根据裂尖应力状态,选用对应于M-C外角点外接圆修正形式(DP1)的参数α和k0代入此公式计算得到的岩石剪切亚临界裂纹扩展长度值与实测值吻合较好,验证了该公式的正确性。岩石剪切亚临界裂纹扩展长度计算公式的建立,可为进一步研究实际工程中的岩石剪切裂纹扩展及止裂问题提供了重要的科学依据。

Shear-box test was used to obtain shear （Mode II） fracture Qf rock. A new formula of sub-critical crack growth length of the shear fracture of rock was established based on the Drucker-Prager （D-P） strength criterion. Microscopic features of shear fracture surface are analyzed by scanning electron microscope （SEM） in order to measure the sub-critical crack growth length of the shear （Mode II） fracture of rock. Results show that the new formula of sub-critical crack growth length has advantages of simple form and easy obtaining of parameters. According to the stress state of crack tip, the value of sub-critical crack growth length calculated by substituting suitable parameters α and ko corresponding to the circumscribed Drucker-Prager （DPI） into the formula is in good agreement with the measured value by SEM. Establishing a correct formula of sub-critical crack growth length will provide an important basis for further studies on the shear crack growth and crack-arrest of rock.