大跨浅埋黄土隧道中系统锚杆受力机制研究

郑州-西安铁路客运专线穿越西北黄土分布的主要地区，而在黄土地区修建跨度超过15.1 m、开挖面积达170 m2的超大断面大跨度铁路隧道洞群在国内尚属首次，相关的设计理论与经验均较为欠缺，尤其是系统锚杆在黄土隧道中的作用机制及锚固效果尚不清楚，使得设计遇到关键难题。为研究大断面黄土隧道中系统锚杆的作用，通过理论推导，阐明了锚杆的作用机制，指出了浅埋大跨度黄土隧道中锚杆的受力原因。采用理论锚杆单元模型，计算得到与实测数据一致的结果，说明该理论模型能够解释浅埋黄土的锚杆受力情况。综合研究表明，浅埋黄土隧道中拱部系统锚杆的锚固效果较弱，而边墙部锚杆的锚固效果显著。

Anchoring mechanism and effect of systematic rockbolt for shallow buried loess tunnel

New-built railway passenger dedicated line from Zhengzhou to Xi’an passes through many districts mostly covered with loess. It’s the first time for China to build such large cross-section tunnel groups in loess zone, which have an area of more than 170 m2 and a span of more than 15.1m. Design theory and relative experience about this type of tunnel in the loess zone is insufficient, especially the anchoring effect and mechanism of systematic rockbolt is unknown. That is a key problem for the large span loess tunnel design. To analyze the effect of systematic rockbolt in the loess tunnel, a formula to explain systematic rockbolt anchoring mechanism is deduced; and the key cause of rockbolt loading in loess tunnel is pointed out. A theoretical model is used to study rockbolt loading; and the calculated results are in good agreement with practical measured data; it is indicated that the theoretical model proposed can give right loading of rockbolt. These results show that in the shallow buried loess tunnel, anchoring effect of systematic rockbolt near the arch is very weak, but systematic rockbolt near the sidewall works well.