分段锚预应力锚杆加固围岩力学分析

Mechanical analysis of surrounding rock reinforced by prestressed bolt with subsection anchor

基于端锚锚杆支护的优越性和围岩破坏分区及破坏深度逐步向深部发展的规律,针对煤矿深部巷道采用加长或全长锚固锚杆支护时,锚杆的锚固段整体受力不均,抗剪切承载能力低,而端锚锚杆无法适应其大变形缺点的问题,建立了两段锚预应力锚杆支护模型。运用理论计算和数值模拟的手段研究了两段锚预应力锚杆锚固段的受力特征和承载能力,并进行了算例对比分析。结果表明:两段锚分区锚固的支护方式明显改变了加长或全长锚固锚杆锚固段的剪应力曲线变化趋势,使原本呈负指数变化趋势的剪应力曲线变得平缓,提高了锚杆锚固段的剪切承载能力;在相同预紧力作用下,与端锚锚杆相比,明显降低了锚杆锚固段的荷载和剪切应力;在不同预紧力下,两段锚预应力锚杆的两锚固段可分别起到围岩不同变形时期端锚锚杆的支护作用,继续发挥端锚支护的优越性。

In this study, a model for a pre-stressed bolt with two anchorage segments was established, by considering both the superiority of point-anchoring bolts and the laws of destruction partitioning and gradually destructive depth development. The model is basically used to solve the following problems. When lengthening-anchoring or fully-anchoring bolts were applied in the deep roadway, the anchorage segments of the anchor was not as uniform as the whole, and the shear capacity was low. While point-anchoring bolts could not adapt to the large deformation. Afterwards the stress characteristics and bearing capacity of two anchorage segments were studied using theoretical calculations and numerical simulations. Moreover, a comparative analysis was also provided in this study. The results show that the bolt with two anchorage segments obviously changes the shear stress curve of the lengthening-anchoring or fully-anchoring bolts, which turns the trend of the original negative exponent into the gentle. Its shear bearing capacity is also improved by the partition supporting pattern with two anchorage segments. Under the conditions of the same pre-stressed force, the load and shear stress of the anchoring section are obviously lower than that of point-anchoring bolts. Under different pre-stressed conditions, these two anchorage sections are separately used as the supporting function of point-anchoring bolts according to various periods of surrounding rock deformation, which continues to show the superiority of point-anchoring bolts.