漳龙高速公路扩建隧道围岩力学特性三维有限元分析

3D Finite Element Analysis on Mechanical Characteristics of Surrounding Rocks of Expansion Project: A Case Study on Houci Tunnel on Zhangzhou-Longyan Highway

为分析隧道扩建过程中围岩的力学特性,确保施工期间围岩的稳定性,以漳龙高速公路后祠隧道扩建工程为依托,建立了反映实际地形的三维有限元模型,对后祠扩建隧道施工期间地表沉降、拱顶下沉、周边位移的特征以及拱脚和拱顶的应力变化规律进行计算分析。计算结果表明:原位扩建隧道位移变化规律不同于普通新建隧道位移变化规律,隧道原位扩建施工过程中,地表沉降曲线表现出了明显的非对称性;隧道掌子面前方12 m及掌子面后方24 m范围内变形较为迅速,为非稳定变形段;根据隧道拱顶位移曲线,提出了针对扩建隧道位移空间变化规律的公式,该公式能预测后祠隧道的变形,从而为施工提供建议和指导;隧道拱脚表现为压应力集中区,随着开挖的进行,拱脚主应力逐渐增大,而拱顶主应力逐渐减小并向拉应力过渡,最终拱顶呈现出较小的拉应力。

To ensure the stability of surrounding rock,the 3D finite element model of Houci tunnel expansion project on Zhangzhou-Longyan highway is established and ground surface settlement, vault subsidence, surrounding rock displacement and variation of stress on tunnel arch feet and crown are analyzed. The calculation results show that： 1）The tunnel displacement law of expansion is different from that of new tunnel construction,and the tunnel displacement curves of expansion shows obvious asymmetry. 2） The deformation speed of the unstable section,12 m in front of and24 m behind tunnel working face,is large. 3） The displacement formulas for expansion tunnel,which can predict the deformation of Houci tunnel,is proposed. 4） The tunnel arch feet show a stress concentration trend. The principle stress of tunnel arch feet increases and that of tunnel invert decreases as the excavation goes on. The stress of tunnel vault develops into small tensile stress in the end.