基于主动支护的木寨岭隧道高地应力软岩大变形预应力锚索支护设计实践

Design Practice of Prestressed Anchor Cable Support Technology for Soft Rock with Extremely High Geostress and Large Deformation in Muzhailing Tunnel

为解决在建木寨岭特长公路隧道薄层极软岩在高地应力下发生的挤压性大变形问题,结合现场展开的工程地质分析、设计变更、监控量测工作,提出一种预应力长短锚索+W型钢带+柔性纤维网组合的基于主动支护的设计方案。该方案采用“先锚后支”的施工工艺,采用数值分析和试验段施工对设计方案进行验证。结果表明,预应力长短锚索组合的主动支护能够充分发挥锚索的锚固和悬吊作用加固围岩,提高围岩的抗剪能力,控制围岩形变能的释放态势,有效控制围岩变形,将初期支护变形控制在20 cm以内,减小约50%。在实际施工过程中对锚索防腐、锚索支护参数及锚索施工设备选型等进行优化调整,确保了隧道施工的顺利进行。

To control severe squeezing deformation of thin extremely soft rock under high geostress in the Muzhailing tunnel under construction,a design scheme based on active support with combination of prestressed long and short anchor cables,W-shaped steel belt,and flexible fiber mesh is proposed based on engineering geological analysis,design changes,and monitoring and measurement work carried out onsite.The scheme adopts the construction order of anchor first and then support.The design scheme is verified by numerical analysis and test section construction.The results show that the active support can fully reinforce the surrounding rock,improve the shear resistance of surrounding rock,control the release state of deformation energy of surrounding rock,effectively control the deformation of surrounding rock,and control the deformation of supporting within 20 cm(that is 50%reduction).In the engineering practice,anticorrosion,support parameters,and construction equipment selection of anchor cable are optimized and adjusted to ensure the smooth progress of tunnel construction.