涨壳式预应力中空锚杆锚固效果及其支护参数优化

Anchorage effect and support parameters optimization of prestressed hollow bolts with expanded shell in rockburst section of tunnel

为探究隧道岩爆地段涨壳式预应力中空锚杆的锚固效果及其支护能力,依托中兰(中卫—兰州)铁路香山隧道工程,利用现场锚固试验,对比分析了涨壳式锚固和其他锚固形式在岩爆隧道中的锚固效果,同时采用有限元数值分析软件MIDAS/GTS NX,分析不同工况下的隧道围岩压力、围岩变形及锚杆轴力对围岩稳定性的影响,进而提出了涨壳式预应力中空锚杆优化后的支护参数,并基于现场实测数据,对涨壳式预应力中空锚杆与普通砂浆锚杆的现场应用效果进行评价。研究结果表明:相对于树脂锚固、水泥药卷以及水泥砂浆锚固形式,涨壳式锚固以其最大的锚固力、支护及时性以及较强的耐久性能,成为本次试验的最优锚固形式,并且能够满足岩爆隧道快速预应力锚固形式施加要求;涨壳式预应力中空锚杆支护参数对围岩稳定性的影响程度从大到小依次为锚杆间距、锚杆长度、预应力、锚杆直径,且直径25mm、间距1.2m、施加预应力80kN、长度3.5m为香山隧道岩爆段涨壳式预应力中空锚杆支护参数的最优组合;相比于普通砂浆锚杆,现场采用涨壳式预应力中空锚杆后,隧道拱顶沉降和水平收敛S1、S2线变形量减小了57.1%、61.9%和64.4%,收敛时间提前了3~5d,拱顶和左、右拱腰围岩压力值减小了32.1%、36.5%和34.2%,进一步验证了涨壳式预应力中空锚杆在岩爆隧道中应用的优越性。

In order to study the anchoring effect and supporting ability of expanded shell prestressed hollow bolt in rock burst section of tunnel,the anchoring effect of expanded shell anchoring and other anchoring forms in rock burst tunnel was compared and analyzed by field anchoring test based on Xiangshan Tunnel Engineering in Zhonglan(form Zhongwei to Lanzhou)Railway,and the finite element numerical analysis software MIDAS/GTS NX was adopted.By analyzing the influence of surrounding rock pressure,surrounding rock deformation and bolt axial force on the stability of surrounding rock under different working conditions,the optimized supporting parameters of the expanded shell prestressed hollow bolt were proposed.Based on the field measured data,the field application effects of the expanded shell prestressed hollow bolt and ordinary mortar bolt were evaluated.The results show that compared with resin anchoring,cement coil anchoring and cement mortar anchoring,expanded shell anchoring is the best anchoring form for its maximum anchoring force,timeliness of support and strong durability,and can meet the requirements of the rapid prestressed anchoring form of rockburst tunnel.The influence degree of extension-shell prestressed hollow bolt supporting parameters on the stability of surrounding rock is bolt spacing,bolt length,prestressed,bolt diameter.The optimal combination of extension-shell prestressed hollow bolt supporting parameters in the rock burst section of Xiangshan Tunnel is 25mm in diameter,1.2min spacing,80kN in prestressed and 3.5min length.Compared with the common mortar bolt,the deformation of S1and S2lines decreased by 57.1%,61.9%and 64.4%compared with the same period of last year,and the convergence time was advanced by 3to 5days.The surrounding rock pressure values of the vault and the left and right arches decreased by 32.1%,36.5%and 34.2%.The application superiority of expanded shell prestressed hollow bolt in rock burst tunnel is further verified.3 tabs,13figs,15refs.