Based on the theory of elasticity and molar-Coulomb strength failure criterion, we proposed the prediction method for hole enlargement ratio in the condition of underbalanced drilling.

基于弹性力学理论及岩石摩尔-库仑强度破坏准则，提出了欠平衡钻井条件下井径扩大率的预测方法。

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When the consolidation ratio is the same, the effect of failure criterion on the dynamic shear strength would reduce with the failure time of vibration increasing.

相同固结比时，破坏标准对动强度的影响随着破坏振次的增加而减小。

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There is a macro-crack and micro-crack system in rocks, which affects almost all the mechanical properties of rocks, especially the failure mechanism and the strength criterion.

岩石内部存在一个宏观的和微观的裂隙系统，岩体的一切力学特性几乎都与这个裂隙系统有关，当然岩体的破坏机理与强度准则也不例外。

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