对拉锚杆、锚索的承载特性与加固效果分析

Analysis for bearing characteristics and reinforcement effect of counter-pulled bolts and cables

随着开采强度的提高,巷道空间层位关系越趋复杂,对拉锚杆、锚索被应用于煤矿巷道支护。现有关于锚杆、锚索的研究基本针对传统锚固方式锚杆、锚索,少有涉及对拉锚杆、锚索,对拉锚杆、锚索的承载特性与加固效果尚不完全清楚。为研究对拉锚杆、锚索的承载特性与加固效果,提出并验证基于FLAC^3D的对拉锚杆、锚索模拟方法,解决FLAC^3D中pile结构单元无法施加预紧力的难题;建立对拉锚杆、锚索拉伸与剪切数值模型,分析全长黏结型与非黏结型对拉锚杆、锚索的轴向与切向承载特性,对比对拉锚杆与对拉锚索的抗剪能力;开展对拉锚杆、锚索阻止结构面剪切滑移和张拉破坏的数值试验,研究对拉锚杆、锚索在原岩应力条件下对结构面剪切滑移和张拉破坏的加固效果。在此基础上,分析对拉锚杆、锚索的适用性。研究结果表明:①所提出的对拉锚杆、锚索模拟方法能够高度仿真对拉锚杆、锚索的结构组成与轴向、切向承载作用;②与非黏结型对拉锚杆、锚索相比,全长黏结型对拉锚杆、锚索对拉伸变形更为敏感,增阻更快,作用范围更大,但也更易在杆体或索体中部破断;③全长黏结型对拉锚杆、锚索的抗剪能力强于非黏结型对拉锚杆、锚索,剪切位移较小时,对拉锚杆的抗剪能力强于对拉锚索,随剪切位移增大,对拉锚索的抗剪能力逐渐强于对拉锚杆;④在原岩应力条件下,对拉锚杆、锚索主要发挥轴向承载作用,可有效阻止煤岩体结构面的张拉破坏,但对煤岩体结构面剪切滑移破坏的控制效果较差;⑤在裂隙岩体加固中,全长黏结型对拉锚杆、锚索的轴力呈“中间高,两边低”分布,易在裂隙位置破断,应注重提高杆、索体的强度。

With the increase of mining intensity,the spatial relationship between roadways becomes more and more complex,and the counter-pulled bolts and cables are used in the roadway support of coal mine.The existing research on bolts and cables is basically directed to the traditional anchoring bolts and cables,and there is little study on the counter-pulled bolts and cables.Therefore,the bearing characteristics and reinforcement effects of counter-pulled bolts and cables are not fully understood.To investigate the bearing characteristics and reinforce-ment effects of counter-pulled bolts and cables,the simulation method of counter-pulled bolts and cables based on FLAC^3D software was proposed and verified.The problem that the pile structure element in FLAC^3D cannot be preloaded is solved in the proposed method.Numerical models for the tension and shear of counter-pulled bolts and cables were established to analyze the axial and tangential bearing characteristics of counter-pulled bolts and cables,and the shear resistances between counter-pulled bolts and cables were compared.Numerical experiment for the counter-pulled bolts and cables preventing the shear sliding of discontinuity was conducted to investigate the reinforcement effect of counter-pulled bolts and cables on the shear sliding of discontinuity under in-situ stress.Numerical experiment for the counter-pulled bolts and cables preventing tension rupture of discontinuities was conducted to investigate the reinforcement effect of counter-pulled bolts and cables on the tension rupture of dis-continuities under in-situ stress.Based on the results,the applicability of counter-pulled bolts and cables was ana-lyzed.The results show that:①the proposed simulation method can exactly simulate the structures and the axial and tangential bearing effects of counter-pulled bolts and cables;②compared with none-encapsulated counter-pulled bolts and cables,the fully-encapsulated counter-pulled bolts and cables are more sensitive to tensile deformation with faster resistance increase and wider supporting range,but are also easier to be broken in the middle of the bodies;③the shear resistance of fully-encapsulated counter-pulled bolts and cables is larger than that of none-encapsulated counter-pulled bolts and cables.When the shear displacement is small,the shear resistance of the counter-pulled bolt is larger than that of the counter-pulled cable.With the increase of the shear displacement,the shear resistance of the counter-pulled cable increases gradually and is finally larger than that of the counter-pulled bolt;④under in-situ stress,the counter-pulled bolts and cables can effectively prevent the tension rupture of discontinuities by mainly exerting axial bearing capability,but their control effect on preventing the shear-sliding rupture of discontinuities is poor;⑤in the reinforcement of jointed rock mass,the axial forces of the fully-encapsulated counter-pulled bolts and cables are distributed as“high in the middle and low on both sides”.The bolts and cables are easy to be broken in the positions of discontinuities,so that special attention should be paid for improving the strength of the bolts and cables.