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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 plane shear (Type II) fracture was obtained by shearing box experiment. The formula of shear subcritical crack propagation length was derived by Drucker-Prager strength criterion and verified by scanning electron microscopy (SEM) at the crack tip of rock specimen. The results show that the calculation formula of rock shear subcritical crack propagation length established by Drucker-Prager strength criterion has the advantages of simple form and easy parameter determination. According to the stress state of crack tip, the circumscribed circle modified form (DP1) The parameters α and k0 substituted into this formula to calculate the rock shear sub-critical crack propagation length values agree well with the measured values, which verify the correctness of the formula. The establishment of the formula for calculating the subcritical crack propagation length of rock shear can provide an important scientific basis for further research on the problem of rock shear crack propagation and crack arrest in practical engineering.