德格隧道冒顶和冒落破坏特征及处治技术

Characteristics of Roof Caving and Rock Falling of the Dege Tunnel and Corresponding Treatment Measures

在川藏公路德格隧道施工中相继出现冒顶和冒落事故。文章利用数值模拟和现场测试对围岩及支护的位移和应力特征进行研究,就同一隧道发生冒顶和冒落的破坏特征和机制进行了深入分析,最后提出了相应的处治措施。研究表明:冒顶破坏以碎屑流变为主,而冒落破坏以碎裂变形为主;冒顶发生时拱顶部碎石土出现塑形变形区,冒落发生时因围岩中形成的竖向与水平方向应力差产生扩容现象;浅埋碎石土围岩自稳能力差,施工扰动引起隧道冒顶破坏发生,而深埋绢云石英片岩裂隙发育,受围岩自重和施工爆破影响诱发隧道冒落破坏。基于以上结论,现场主要采用了限制塑性变形及碎裂变形扩展、施作锚注支护体系、实施“强行”联合支护和加强支护参数等关键措施。

Roof caving and rock falling occurred during the construction of Dege tunnel on the Sichuan-Tibet high? way. The characteristics of displacement and stress of surrounding rock and support were studied by numerical simulation and site test, a thorough analysis was carried out regarding the features and mechanism of roof caving and rock falling occurred at the same tunnel, and some corresponding treatment measures were proposed. The research results show that roof caving was represented by debris flow and rock falling was represented by cracked deformation;plastic zone of crushed stone occurs at tunnel crown in the course of roof caving and dilatancy occurs due to the difference of vertical stress and horizontal stress in the course of rock falling;roof caving is caused by construction disturbance due to poor self-stability of shallow-buried crushed rock mass and rock falling is induced by dead load of rock mass and blasting construction attributed to developed fissure of deep-buried sericite quartz schist. The main corresponding measures include restriction of plastic deformation and cracking development, installation of anchoring and injection support system, implementation of forced composite support and strengthening of the support parameters.