三峡库区公路陡高边坡拉裂-滑塌型危岩破坏机制分析

Analysis on the Failure Mechanism of Tensile Fracture-Sliding of Unstable Rock with Steep Slope in the Three Gorges Reservoir Area

【目的】探究公路陡高边坡危岩的失稳破坏机制,对确保公路交通交通安全具有重要意义。【方法】针对三峡库区公路陡高边坡中受2组结构面切割控制形成的危岩,分析了首先受控于近水平层状第一条主控结构面逐渐受拉扩展,扩展至一定程度沿陡倾卸荷裂隙面第二条主控结构面滑移变形破坏的拉裂-滑塌型危岩地质模型。考虑危岩块间的相互作用,通过转角判断相邻危岩块的荷载传递;基于断裂力学方法构建了危岩体在自重与振动荷载作用下第一主控结构面拉断裂方程与破坏判别式,利用极限平衡理论构建了第二主控结构面在自重与振动荷载下的滑塌失稳判别式。通过对发生2007年11月20日三峡库区宜万铁路高阳寨隧道口20m外的拉裂-崩塌型危岩破坏,分析了被2组结构面切割面形成的3块近临空面附近的危岩位于国道318线K1405上方,在自重与工程振动荷载作用下危岩失稳破坏机制。【结果】经计算发现,针对水平状第一主控结构面,底部危岩块与中间危岩块层面间受压,不会拉裂,底部与中间危岩块联合与顶部第三危岩块层面间也不会拉裂破坏,3块危岩块联合一体后顶部层面会被拉裂扩展,导致陡倾的第二主控结构面滑塌失稳破坏坠落解体。【结论】计算结果与实际情况基本吻合,验证了含两条主控结构面的拉裂-滑塌型危岩的稳定性分析法的合理性,为危岩防治提供了重要的理论依据。

[Purposes]To explore the instability and failure mechanism of dangerous rocks in steep high slope of highway,which is of great significance to ensure the traffic safety of highway.[Methods]For highway slop in the Three Gorges Reservoir by 2 group of unstable rock structural plane cutting control live,it analyzed the first controlled by nearly horizontal layered first master structure surface tension gradually expand,expanded to a certain degree along the steep tipping fracture plane of the second master slip deformation and failure of structural surface cracking,slump type dangerous rock geological model.Considering the interaction between dangerous rock blocks,the load transfer of adjacent unstable rock blocks is judged by the angle of rotation.Based on the method of fracture mechanics,the failure discriminant of the first master controlled structural plane under dead weight and vibrating load is constructed,and the collapse and instability discriminant of the second master controlled structural plane under dead weight and vibrating load is constructed by using the limit equilibrium theory.Based on the rupture and collapse of the dangerous rock 20 meters away from the entrance of Gaoyangzhai Tunnel of Yiwan Railway in the Three Gorges Reservoir area on November 20,2007,it analyzes the instability and failure mechanism of the dangerous rock which is located above the national Highway 318 line K1405 and formed by the cutting surface of two groups of structural planes.[Findings]The calculation,found that the first master structure for horizontal surface,unstable rock at the bottom and middle unstable rock block level compression,not cracking,bottom and middle dangerous rock joint and top nor between the third level of unstable rock cracking destruction,three pieces of unstable rock after the unity at the top level will be pull-apart extension,lead to steep dip second master fall in instability and failure of structural plane sliding collapse.[Conclusions]The calculated results are basically consistent with the actual situation,which verifies the effectiveness of the stability analysis method for unstable rocks with two main control fissures,and provides an important theoretical basis for the prevention and treatment of unstable rocks.