泥质粉砂岩地层浅埋联拱隧道锚杆支护效果

Bolt Support Effect of Shallow-buried Multi-arch Tunnel in Argillaceous Siltstone Stratum

锚杆在软弱围岩等特殊地层中的作用效果一直是近几年的研究热点。为了明确泥质粉砂岩地层中系统锚杆的作用效果,通过现场监测的方法研究了泥质粉砂岩地层联拱隧道取消锚杆试验段与布设锚杆试验段拱顶沉降、水平收敛、围岩压力以及钢拱架内力等监测项目的变化规律和异同。结果表明:取消锚杆试验段拱顶沉降、水平收敛与布设锚杆试验段差别不大;取消锚杆试验段围岩压力略大,但分布较为均匀,试验段围岩压力均小于理论计算值;联拱隧道先开挖洞拱架内力大于后开挖洞,布设锚杆试验段由于锚杆约束拱架的作用导致拱架受力较小;隧道大部分位置锚杆受压,轴力范围为-4.45~4.23 kN,最大拉力占杆体极限拉力值的2.35%,锚杆抗拉效用无法得到充分发挥。

The effect of bolt in soft surrounding rock and other special strata has been a hotspot of research in recent years.To clarify the effect of systematic anchor in clayey siltstone strata,variations and similarities of monitoring items were studied in clayey siltstone stratum in on-site monitoring method.The monitoring items included vault settlement,horizontal convergence,surrounding rock pressure,and internal force of steel arch frame with or without anchoring.Results reveal that the difference in vault settlement and horizontal convergence between test sections with or without anchoring is very little.The wall-rock pressure of the test section without anchoring is slightly greater and distributed evener,and smaller than the theoretical calculation value.The internal force of the arch frame of the double-arch tunnel excavated earlier is greater than that of the tunnel excavated later.The stress of the arch frame is smaller in the test section with anchoring because of the restraint of the arch frame by anchors.Most parts of the tunnel are under compression,and the axial force ranged from-4.45 kN to 4.23 kN.The maximum tension is accounted for 2.35%of the ultimate tension value of the bolt,and the tension effect of the bolt can not be fully played.