粉煤灰地层浅埋大断面连拱隧道预加固方式研究

Research on Pre-reinforcement Method of Shallow Buried Large-section Double-arch Tunnel in Fly Ash Stratum

由于粉煤灰地层本身工程性质较差,隧道开挖时不同工序及支护方式的变化也极易影响掌子面的稳定及支护结构的安全。本文结合盐坪坝隧道埋深浅、跨度大、穿越不良地层粉煤灰地层的特点,对浅埋暗挖大断面隧道工程中常用的地层预加固方式做简要介绍并分析其适用性,结合现场实际,提出了一种适用于粉煤灰地层大断面连拱隧道的预加固技术,主要采用高压旋喷桩对穿越粉煤灰地段实施地表加固,从现场施工情况来看,盐坪坝隧道现已成功贯通,期间没有发生掌子面坍塌、地表沉陷等情况。

Due to the poor engineering nature of the fly ash stratum,the changes in different working procedures and support methods during tunnel excavation can also easily affect the stability of the tunnel face and the safety of the support structure.This article combines the characteristics of Yanpingba Tunnel with shallow depth,large span,and fly ash stratum through unfavorable strata,briefly introduces the pre-reinforcement methods commonly used in shallow-buried tunnels with large cross-sections,and analyzes its applicability.Combining with site reality,A pre-reinforcement technology suitable for large-section double-arch tunnels in fly ash stratum is proposed.High-pressure jet grouting piles are mainly used to reinforce the surface of the fly ash section.Judging from the on-site construction situation,the Yanpingba tunnel has been successfully penetrated.During the period,there was no collapse of the tunnel face or ground subsidence.