Rock bolts are highly important underground to prevent falls of ground and thus, ensure safety. In situ, the ground reinforcement is subjected to a combination of loads, such as shear, tensile, and/or bending loads. Studies have been conducted to evaluate the effect of either shear, tensile, or bending loads on the ground support. However, only a few studies have been done to evaluate the effect of combined load on the rock bolt performance. In situ, the order of loads acting on the bar cannot be predicted, and more than one load can act on the bar at the same time. Thus, a hybrid failure criterion was developed that covered all combined loading conditions. Fifty-eight un-grouted laboratory rock bolt tests were conducted in total under two load conditions: applying shear displacement to the rock bolt and then tensile load to failure, and applying tensile displacement to the rock bolt and then shear load to failure. From the test results, the failure criterion was developed based on regression analysis. A nonlinear relationship was determined for the loading condition variations. The failure criterion presented in this paper can be used as a guide in the rock bolt capacity design under all loading conditions.

中文翻译：

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硬岩矿岩锚组合载荷失效判据

锚杆在地下非常重要，可以防止地面坠落，从而确保安全。在现场，地面钢筋承受多种载荷，例如剪切载荷、拉伸载荷和/或弯曲载荷。已经进行了研究来评估剪切、拉伸或弯曲载荷对地面支撑的影响。然而，只有少数研究来评估组合载荷对岩石锚杆性能的影响。在原地，无法预测作用在杆上的载荷顺序，并且可以同时作用在杆上的载荷不止一个。因此，开发了涵盖所有组合载荷条件的混合失效准则。在两种载荷条件下总共进行了 58 次未灌浆的实验室岩石锚杆试验：对岩石锚杆施加剪切位移，然后向断裂施加拉伸载荷，并对锚杆施加拉伸位移，然后剪切载荷破坏。根据测试结果，基于回归分析制定了失效准则。为加载条件变化确定了非线性关系。本文提出的破坏准则可用作所有载荷条件下岩石锚杆容量设计的指南。