适用于围岩大变形的螺纹钢锚杆设计及工程实践

Design and engineering practice of rebar bolt for large deformation roadway

  • 摘要: 矿用锚杆自20世纪90年代已开始大规模应用,但目前其螺纹几何参数仍与土木行业钢筋相同。钢筋螺纹是针对地面无地应力、且支护体变形控制在弹性阶段的钢混结构而设计,随着深部资源开采进展,地下巷道出现围岩大变形,原基于地面建筑的钢筋螺纹几何参数需针对高地应力、软岩大变形等地质条件进行优化。基于锚固力学载荷传递机理,明确螺纹钢螺纹是锚杆支护承载者,锚杆锚固性能与螺纹几何参数密切相关;通过分析锚固段的破坏方式,将锚固段破坏分为平行剪切破坏和剪涨滑移破坏;进一步通过分析2种破坏过程,阐明了螺纹几何参数(包括杆体直径、螺纹上升角、肋宽、肋坡角、肋高、肋间距)对锚固性能的影响和作用。针对深部资源开采,综合考虑巷道围岩的变形控制及离层控制,研发了一种适用于围岩大变形的新型螺纹钢锚杆,该设计通过螺纹几何优化提高了锚固段的峰后残余强度,通过增加锚固段吸能能力有效提高大变形围岩体的岩层控制能力。对新螺纹钢锚杆进行了实验室锚固力测试和现场拉拔试验,结果显示,围岩大变形锚杆平均拉拔力峰值比矿用左旋锚杆分别提高了13%和16%;从能量吸收的角度,新锚杆在实验室和现场的平均吸能较左旋锚杆提高了15%和55%,表明围岩大变形锚杆的锚固性能优于矿用的左旋锚杆。进一步对新设计锚杆进行了工业试验,在深部回采巷道设计安装了3种锚网支护方式,通过对比分析断面收敛量、顶板离层量、杆力及锚杆宏观破断失效方式等,进一步验证了新设计的围岩大变形锚杆支护更有利于深部巷道的岩层控制。

     

    Abstract: Rebar rock bolt has been widely used in the mining industry since 1990′s, however, its thread geometric parameters are still the same as those of steel tendon used in civil engineering, which is designed for the steel-concrete structure without ground stress and the deformation of the structure is normally within elastic stage. With the development of deep resource mining, the surrounding rock of the underground roadway has large deformation. The geometric parameters of the rebar bolt designed for the ground building should be optimized for the geological conditions such as high ground stress and large deformation of soft surrounding rock. Based on the load transfer mechanism of anchorage mechanics, this paper clarifies that the rib of the rebar is the bearing body of bolt support, and the anchorage performance of the bolt is closely related to the geometric parameters of the rib. By analyzing the failure mode of anchorage, the failure mode of the anchorage section is classified as parallel shear failure and dilational slip failure. Furthermore, by analyzing two failure processes, the influence of the geometric parameters of rebar rib (including rod diameter, rib slope angle, rib width, rib rise angle, rib height and rib spacing) on anchorage performance are clarified. Aiming at deep resource exploitation, a new type of rebar bolt designed for the large deformation of surrounding rock is developed by comprehensively considering the deformation control and separation control of surrounding rock. The design improves the residual strength of anchorage section through thread geometry optimization, it effectively improves the strata control ability of large deformation surrounding rock by increasing the energy absorption. Pullout tests were conducted in the laboratory and in the field. Results show that the average peak pull-out forces of the new bolt are 13% and 16% higher than that of the left-spiral bolt, respectively. From the perspective of energy absorption, the average energy absorption of the new bolt is 15% and 55% higher than that of the left-spiral bolt, indicating that the anchoring performance of the new bolt designed for large deformation surrounding rock is better than that of the left-spiral bolt. Furthermore, the application of the new designed bolt is carried out. Three sections of rock bolting support roadway are designed and installed in a deep mining roadway. Through the comparative analysis of roadway convergence, roof separation, bolt bearing force and the failure mode of the bolt, it is further verified that the new designed bolt support is more conducive to the strata control of deep underground roadway.

     

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