软弱泥质页岩隧道衬砌受力特征探讨

Discuss of mechanics characteristic of tunnel lining at softening shale stratum

通过对关口垭隧道泥质页岩条件下软弱地段支护系统的现场测试,得到了钢支撑、喷射混凝土和二次衬砌等支护构件的受力状况与软弱泥质页岩地质状况之间的关系,建立相应的模型,进行了三维有限元数值分析,并对测试与计算结果进行了分析。结果表明:围岩应力前期释放较快,而后期变形压力延续时间长,除钢支撑承担了较大的围岩初始释放压力外,二次衬砌也承担了较大比例的长期变形压力,为了有效地约束围岩早期的快速变形和后期的长期变形,初期支护和二次衬砌都应具有足够的强度和刚度;现行《公路隧道设计规范》所推荐的围岩松动压力计算方法,对于软弱泥质页岩隧道并不完全适用,在进行围岩类别划分时应适当降低围岩类别;施工掘进时必须控制好各工序的施工距离,尽快使初期支护体系形成封闭环,并加设锁脚锚杆等辅助措施,以便有效地改善围岩地受力状况。

<Abstrcat>By measuring the supporting system of Guankouya tunnel at softening shale stratum, the relationship between the stress of the surrounding rock masses about I-steel supporting, secondary lining and the geological of softening dunn bass stratum is obtained.The model is set, and 3-D finite element numerical calculating is made. The results of the survey and the computing are analyzed and discussed. These results shows that surrounding rock stress releases rapidly in the early stage while the continue time of the deformation compressive stress is long, and that I-steel bears major releasing stress, the secondary lining bears much great proportion deformation compressive stress. The initial shoring and the secondary lining should be provided with adequate intensity and rigidity so as to restrict the fast deformation in the forepart and the long-term deformation in the forepart; the computing formula of the flexible compressive stress about the surrounding rock commended by Highway Tunnel Design Specification is not absolute applicable to the softening shale tunnel, and the surrounding rock class should be proper cut down in the design. Distance between production processes also must be controlled in the process of construction, and locking-feet anchor rod should be set, while forming the closed-loop to the supporting system as to improve surrounding rock stress effectively. These provide a sound basis for the tunnel design of at this type geological condition.