板岩隧道顺层塌方分析及预防失稳措施研究

Study and Countermeasure for Collapse Instability of Tunnel in Slate

为避免板岩隧道围岩楔形体掉块和顺层塌方的发生,针对板岩的力学性质和变形特性,从隧道施工方面对板岩隧道围岩的工程特性和易形成塌方的地质构造类型进行总结,并以半山隧道初期支护长段落顺层塌方为例进行深入的分析和研究。结果认为:当顺层构造岩层和节理产状与隧道走向夹角较小、多组节理相互切割与岩层面形成不利结构面组合长段落斜穿隧道时,受施工开挖爆破震动、地下水浸润、重力作用以及大断面开挖形成临空面的影响,围岩及支护结构局部薄弱处出现失稳破坏,由于牵引作用不断扩大并持续发展造成较长段落的坍塌。最后,提出了顺层构造、节理密集带和隧道开挖后不利结构面组合对围岩稳定性的影响分析方法,针对板岩地质隧道施工提出了预防围岩失稳的措施和支护结构的优化措施。

In order to avoid the occurrence of slabs and bedding collapse of the surrounding rock wedge of tunnel inslate, analysis of long section of bedding collapse of Banshan Tunnel with primary support is carried out; the mechanicalproperties and deformation characteristics of slate are studied; and the engineering characteristics of surrounding rock ofthe tunnel in slate and the geological structure type prone to collapse are summarized in terms of tunnel construction. Theresults show that： the traction increasing and continuous developing induced long section of bedding collapse occurs afterinstability of local weak points of surrounding rock and lining under the comprehensive influences of excavation blastingvibration, groundwater infiltration, gravity and large cross-section excavation induced free face when the angles betweenbedding structure rock or joint occurrence and tunnel are small and the tunnel crosses long unfavorable structural planegenerated by intercuting between multi-group joints and form. Finally, an analysis method for the influence of thebedding structure, the joints and unfavorable structural plane of the tunnel excavation on the stability of surrounding rockis proposed. The measures to prevent the instability of the surrounding rock and the optimization of the support structureare put forward.