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湘桂线石头岗隧道下穿衡昆高速工程,在对85m超长Φ159m大管棚内力现场测试分析基础上,建立精细化的数值模型对长管棚作用机理进行研究.提出管棚预支护结构受力的纵向可按掌子面前方受拉段、掌子面后方受压段、靠近洞口受拉段分为Ⅰ,Ⅱ,Ⅲ区,其中:Ⅰ区呈凸起分布,峰值位于掌子面前方一定距离处;Ⅱ区为凹形分布,计算峰值位置滞后掌子面一定距离;Ⅲ区自洞口向内呈逐步减小趋势,峰值位于洞口处.各区间长度除Ⅰ区维持基本不变外,Ⅱ和Ⅲ区间长度随掌子面掘进而增长;各区内管棚受力也随隧道掘进而增长,且表现为先快后慢趋势.
On the basis of on-site testing and analysis of internal force of 85m long Φ159m pipe roof, a detailed numerical model was established to study the mechanism of long pipe shed. The longitudinal direction of the force may be divided into Ⅰ, Ⅱ, Ⅲ areas by the tension section in front of the face and the compression section in the back of the face, and the tension section near the hole entrance, in which: Ⅰ area is convex and the peak is in front of the palm The area is located at a certain distance, and the area Ⅱ is a concave distribution, and the peak position lags behind the facet of a certain distance. The area Ⅲ gradually decreases from the entrance to the entrance and the peak is located at the entrance. The length of sections Ⅱ and Ⅲ increased with the excavation of the palm face. The stress of the pipe roof in each area also increased with the tunneling, and showed the trend of first fast and slow down.