The effective reinforcement of two or more overlying layers of mine openings in a single installation is usually done by coupling of two standard rock bolts mainly during the extraction of medium-thick coal seams. However, field observations show that the couplers of multiple bolts often degrade or break mostly at their connections. These types of failures can be avoided by strengthening the couplers of such multi-bolts assemblies. To achieve this, a novel threaded coupler system with an expansion shell was suggested in this paper. The newly designed coupler consists of a threaded tapered-plug-cum-connector with an expansion shell for connecting and tightening two standard rock bolts. An analytical model for evaluating the load distribution along the coupler subject to axial load was derived. Numerical analysis was performed to analyse the load transfer, deformation, and strains across the coupler including the factor of safety for the bolt-coupler-resin and bolt-coupler-expansion shell. The results validated the analytical model of the proposed coupler design, which provides better anchorage near the interface of the host rock mass. Thus, the developed coupler design would reduce the failures of the proposed coupler and stabilize laminated roof strata above the medium-thick coal seams in underground mines.

在一次安装中，通常通过两个标准岩石锚杆的连接（主要是在开采中厚煤层的过程中）有效地加固两层或更多层矿井口。但是，现场观察表明，多个螺栓的连接器通常在连接处经常退化或断裂。可以通过加强此类多螺栓组件的连接器来避免这些类型的故障。为了达到这个目的，本文提出了一种带有扩展壳的新型螺纹连接器系统。新设计的连接器包括一个带膨胀外壳的带螺纹的锥形插头兼连接器，用于连接和拧紧两个标准的岩石螺栓。推导了用于评估沿轴向载荷的沿耦合器的载荷分布的分析模型。进行了数值分析，以分析整个耦合器上的载荷传递，变形和应变，包括螺栓耦合器树脂和螺栓耦合器扩展壳的安全系数。结果验证了所提出的耦合器设计的分析模型，该模型可在主体岩体的界面附近提供更好的锚固。因此，开发的耦合器设计将减少所提出的耦合器的故障并稳定地下矿井中厚煤层上方的层状顶板地层。