软弱围岩下铁路隧道支护结构受力监测与分析

Monitoring and Analysis of Support Structure Stress of Railway Tunnel under Soft Surrounding Rock Condition

以宝兰客专朱家山隧道为工程背景,通过现场监测,研究了围岩压力、钢架应力、初支混凝土应力、初支与二衬接触压力和二衬混凝土应力等参数随时间变化的规律及空间分布特征。研究结果表明:Vb级围岩压力大于IVb级,但压力分布均性要比IVb级好,IVb级断面左侧围岩压力大于右侧;钢架整体处于受压状态,Vb级断面分布不均性比IVb级更明显,Vb级拱顶、左拱脚处应力超过200 MPa;两类围岩初支混凝土应力分布不均,部分位置施工过程中均表现为拉应力,仰拱处初支混凝土应力较其他位置大很多,超过了容许值;初支与二衬接触压力在二衬施做后迅速增大后减小并趋于稳定,断层破碎带承载能力降低的问题得到改善;二衬混凝土应力分布不均;拱顶、右拱腰及右墙中出应力较大,尤其是拱顶处应力最大,已超过容许值;综合量测结果,部分位置钢架和混凝土受力过大,甚至超过了容许值,故需采取适合的施工控制措施。

Based on the engineering background of Zhujiashan Tunnel on Baoji-Lanzhou Passenger Dedicated Lines,the rule of the parameters changing with the time and the spatial distribution characteristics were studied by in-situ monitoring,such as surrounding rock pressure,steel frame stress,the initial support concrete stress,the initial support and inner lining contact pressure and second lining concrete stress.The research results show that the surrounding rock pressure of Vb class rock is larger than that of IVb class rock,but the pressure distribution uniformity of Vb class rock is better than that of IVb class rock; the surrounding rock pressure of left side is larger than that of the right side for IVb class rock. The whole steel frame is in the state of compression and the uneven distribution of Vb section is more obvious than that of IVb; the stress of vault and left arch foot of Vb class rock exceeds 200 MPa.The initial support concrete stress distribution of the two types of surrounding rock is uneven,and some parts are tensile stress during construction; the initial support concrete stress of the inverted arch is much larger than that in other locations,exceeding the allowable value. After inner-lining construction,the initial support and inner lining contact pressure increase in a short time and then reduce to a stable value. That means the problem of bearing capacity reduction in fault fracture zone has been improved. The distribution of second lining concrete stress is not uniform; the stress of vault,right arch waist and wall middle are larger; especially the stress of the vault is the largest and exceeds the allowable value. Based on all monitoring results,the stress of steel frame and concrete in some places is too large and even exceeds the allowable values. Therefore,appropriate construction control measures need to be taken.