The application of ductile rock bolts has been a crucial method for solving the problems of large deformations, energy absorption and stability control issues in deep rock masses. To study the anchoring mechanism of the key expansive structure, this paper proposes a novel type of bolt — the Ductile-Expansion bolt, and conducts research on anchoring mechanics, energy absorption characteristics, and failure modes of the bolt. In addition, this paper defines the concept of load-volume ratio of metal rock bolts and proves the Ductile-Expansion bolt is capable of better improving the unit volume bearing capacity of the bolt material. Furthermore, laboratory and field tests verify the Ductile-Expansion bolt had better anchoring effect than the traditional rebar bolt, with the expansion structure favorably enhancing the ductility and energy absorption performance of the bolt. Finally, this paper microscopically analyzes the crack propagation and distribution morphology of the bolts by establishing a 3D coupled numerical model based on FDM-DEM. Numerical results illustrate the interface at the variable diameter of the Ductile-Expansion bolt serves as the transition zone between high and low stress levels. The expansion structure can impose radial compression on the medium around the bolt, which can improve the bolt anchorage performance.

中文翻译：

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延性膨胀螺栓的锚固机械特性


韧性岩石锚杆的应用一直是解决深部岩体中大变形、能量吸收和稳定性控制问题的关键方法。为研究关键膨胀结构的锚固机理，本文提出了一种新型螺栓——延性膨胀螺栓，并对螺栓的锚固力学、吸能特性和失效模式进行了研究。此外，本文定义了金属岩石锚杆的载荷-体积比的概念，证明了延性膨胀锚杆能够更好地提高锚杆材料的单位体积承载能力。此外，室内和现场测试验证了延性膨胀锚杆比传统钢筋锚杆具有更好的锚固效果，膨胀结构有利于提高锚杆的延展性和吸能性能。最后，通过建立基于 FDM-DEM 的三维耦合数值模型，微观分析了螺栓的裂纹扩展和分布形貌。数值结果表明，延性膨胀螺栓的可变直径处的界面用作高应力水平和低应力水平之间的过渡区。膨胀结构可以对螺栓周围的介质施加径向压缩，从而提高螺栓锚固性能。