With the increase of the coal mining depth, the surrounding rock shows characteristics of high stress and large deformation. However, the traditional bolt could not adapt to this surrounding rock environment and become invalid due to low elongation. In order to solve the problem, the new type of yielding bolt has been designed. It could release the deformation energy of the surrounding rock through its yielding pipe. However, few studies have been reported on the mechanism in bearing capacity decrease of the yielding pipe. Furthermore, the evaluation of the yielding bolt was not fully understood. Under such a background, a numerical model of the yielding model was established. According to the numerical simulation, the mechanism of the decrease in the bearing capacity of the yielding bolt is that the buckling occurs at different positions of the yielding pipe, making the material stiffness matrix turn negative, and the bearing capacity decreases significantly. Also, the performance of the yielding bolt could be evaluated from the use efficiency of the yielding pipe, the plastic strain characteristics of the components of the yielding bolt, and the energy absorption law. The evaluation results indicated that: (a) the deviation of the yielding pipe's Mises stresses was within the range of 1.0%‐4.0%. The stresses were distributed evenly, and the material use efficiency was high; (b) only the yielding pipe occurred the plastic failure during the yielding process, and other components were at the elastic stages. After the yielding, the yielding bolt was still effective for support. (c) The yielding pipe could absorb energy smoothly, which is helpful for the stability of the yielding bolt.

中文翻译：

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煤矿井下锚杆承载力下降机理及性能评价。

随着采煤深度的增加，围岩具有应力高，变形大的特点。然而，传统的锚杆不能适应这种围岩环境，并且由于伸长率低而变得无效。为了解决该问题，已经设计了新型的屈服螺栓。它可以通过其屈服管释放围岩的变形能。但是，关于屈服管承载力下降的机理的研究很少。此外，屈服螺栓的评估还没有被完全理解。在这种背景下，建立了屈服模型的数值模型。根据数值模拟 屈服螺栓承载力下降的机理是屈曲发生在屈服管的不同位置，使材料刚度矩阵为负，承载能力明显下降。同样，可以根据屈服管的使用效率，屈服螺栓的组件的塑性应变特性以及能量吸收规律来评估屈服螺栓的性能。评估结果表明：（a）屈服管的米塞斯应力的偏差在1.0％-4.0％的范围内。应力分布均匀，材料使用效率高。（b）在屈服过程中，只有屈服管发生塑性破坏，其他部件处于弹性阶段。屈服之后 屈服螺栓仍然可以有效地支撑。（c）屈服管可以平稳吸收能量，有利于屈服螺栓的稳定性。