节理围岩台阶法隧道锁脚锚管支护参数研究

Study on Design Parameters of Feet-Lock Pipes for Bench Cut Tunnels in Jointed Rocks

应用平面应变有限单元法,考虑软弱节理围岩的各项异性本构特征,研究台阶法隧道采用锁脚锚管作为沉降控制措施的加固效果,分析锁脚锚管关键参数对支护效果的影响。结果表明,在研究条件下,增设锁脚锚管后,隧道拱顶沉降有所减小,初期支护内力显著增大。相对而言,增加锁脚锚管长度对支护效果的影响较不明显。增大锁脚锚管安装角度时,锁脚锚管对拱顶沉降的限制作用减小,同时支护结构内力先增大后减小。根据研究结果,建议软弱节理围岩中浅埋大跨隧道采用台阶法施工时锁脚锚管的合理长度约为4 m,与竖向间的合理角度约为40°-60°。

The supporting effects of feet-lock pipes for bench cut tunnels in jointed rocks are studied using the plane strain finite element method,with consideration of anisotropic constitutive behaviors of jointed rocks in which the tunnel is constructed.The results show that,compared to the tunnels without feet-lock pipes,the crown settlement of the tunnel will be decreased after the feet-lock pipes are applied,and the internal forces of the preliminary supporting system will be increased significantly.Comparatively,the increase of the length of the feet-lock pipes can only slightly influence the supporting results.When the installed angle of feet-lock pipes is increased,the restriction effect of feet-lock pipes on tunnel settlement is decreased,and the internal forces of the supporting structures first increase,and then decrease.Based on the studied results,it is recommended that the appropriate length of the feet-lock pipes in bench cut tunnels constructed in weak jointed rocks with shallow burial depth can be taken to be about 4 meters,and the installed angle between the feet-lock pipes and the vertical line can be between 40°and 60°.