Wellbore instabilities frequently occur in mudstone formation with weak plane bedding because of strong anisotropies. The mechanics parameters of weak plane bedding are of vital significance to the wellbore stability analysis for mudstone formations. The conventional method for determining the mechanics parameters is to fit lots of triaxial test data due to the blindness of coring. In this paper, an evaluation method of the mechanics parameters of weak plane bedding is proposed to improve the accuracy of weak plane bedding mechanical properties. The mechanics parameters of weak plane bedding are obtained by combing the single-weak plane failure criterion with the compressive strength of rock obtained by the triaxial test of cores with different coring angles. It is seen that the new evaluation method is simple and convenient. On the other hand, a validation method of the mechanics parameters of weak plane bedding is proposed to ensure their accuracy. The compressive strength obtained from the core with the special coring angle is compared with the theoretical compressive strength for verifying the accuracy of weak plane bedding mechanical properties. It is observed that the proposed evaluation and validation methods can be used to measure the value of weak plane bedding mechanical properties precisely. The proposed methods are general and can be used for measuring the mechanical properties of fracture weak-plane and joint weak-plane.

中文翻译：

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泥岩中弱平面层理力学性质的分析与试验研究

由于各向异性强，在具有弱平面层理的泥岩地层中经常发生井筒不稳定性。弱平面层理的力学参数对泥岩地层井筒稳定性分析具有重要意义。由于取芯的盲目性，传统的力学参数确定方法是拟合大量的三轴试验数据。本文提出了一种弱平面层理力学参数的评价方法，以提高弱平面层理力学性能的准确性。弱平面层理的力学参数是将单弱平面破坏准则与不同取心角岩心三轴试验得到的岩石抗压强度相结合得到的。可见，新的评价方法简单方便。另一方面，提出了弱平面层理力学参数的验证方法，以确保其准确性。将具有特殊取心角的岩心获得的抗压强度与理论抗压强度进行比较，以验证弱平面层理力学性能的准确性。据观察，所提出的评估和验证方法可用于精确测量弱平面层理力学性能的值。所提出的方法具有通用性，可用于测量断裂弱面和接头弱面的力学性能。将具有特殊取心角的岩心获得的抗压强度与理论抗压强度进行比较，以验证弱平面层理力学性能的准确性。据观察，所提出的评估和验证方法可用于精确测量弱平面层理力学性能的值。所提出的方法具有通用性，可用于测量断裂弱面和接头弱面的力学性能。将具有特殊取心角的岩心获得的抗压强度与理论抗压强度进行比较，以验证弱平面层理力学性能的准确性。据观察，所提出的评估和验证方法可用于精确测量弱平面层理力学性能的值。所提出的方法具有通用性，可用于测量断裂弱面和接头弱面的力学性能。