浅埋暗挖软基隧道分部开挖拱脚地基承载力研究

Study on the Bearing Capacity at Arch Toot of Shallow Buried Soft Base Tunnel with Partial Excavation

针对目前浅埋暗挖软基隧道在分部开挖条件下支护结构拱脚受力进行专门理论计算分析的报道尚不多见的现状,基于Winkler弹性地基梁理论建立管棚超前支护和锁脚锚杆的力学模型,提出两者对支护结构竖向荷载的承载作用计算方法,并在此基础上推导拱脚地基荷载的计算公式,并进行实例计算分析。计算结果结合现场拱脚压力测试结果表明:提出的拱脚地基荷载计算方法可靠性良好,能够很好地解释地表过量沉降以及隧道中上部开挖步为位移控制关键步序的原因,提出浅埋暗挖软基隧道分部开挖时应重视对拱脚地基承载力进行验算,承载力不足时应采取措施,避免因此造成的隧道和地层整体沉降。

In view of the fact that special theoretical analysis of the stress at the foot of supporting structure of shallow buried soft base tunnel with partial excavation is rarely reported, mechanical models and corresponding calculation method of vertical-load-bearing role of pipe-shed advance support and foot-locking bolt are established respectively based on the elastic theory of Winkle. Based on these, formulas of foundation load at the arch foot are obtained and applied in real calculation. Results of both calculation and field tests on arch foot pressure show that the proposed calculation method is reliable to calculate the load at the arch foot and helpful to explain the reason why excessive surface settlement takes place and why the upper-middle excavation step is the key to control displacement. It is recommended that the foundation capacity at the arch foot of shallow buried soft base tunnel should be checked when partial excavation is executed, and necessary measures be taken if the foundation capacity is not sufficient to avoid general settlement of the tunnel and the stratum.