基于BOTDA光纤传感技术的盾构隧道变形感知方法

DEFORMATION SENSING METHOD OF SHIELD TUNNEL BASED ON OPTICAL FIBER SENSING TECHNOLOGY OF BOTDA

盾构隧道横断面收敛变形是评价隧道结构性态的重要指标。由预制管片拼装而成的盾构隧道,接头刚度显著低于管片刚度,因此,其横断面变形主要集中在接头张开及管片转动部位。针对盾构隧道横断面变形特点,提出考虑分布式光纤传感技术空间分辨率的点式固定方法,测量相邻管片接头两侧的相对位移。运用几何学原理,对管片接头张开、管片转动及隧道变形进行分析。通过2组不同轴力下的盾构隧道接头室内原型试验验证该方法,结果表明该方法可以有效感知盾构隧道横断面变形。采用该方法长距离布设光纤,可形成盾构隧道变形感知神经网络,提高监测密度,实现长距离、高密度、高精度、低成本的盾构隧道变形健康监测,从而保证地铁隧道的运营安全。

Transverse deformation is basically regarded as a key index to evaluate structural behaviors of shield tunnels. The joint stiffness in shield tunnel is always weaker than segmental lining. Therefore the transverse deformation of shield tunnel is mainly governed by opening of joint and rotation of segmental lining. This paper presents a deformation sensing method using two-point fixed pretension fiber based on distributed optical fiber sensing technology, i.e. Brillouin optical time domain analysis（BOTDA）. Both the spatial resolution of analyzer and the pattern of transverse deformation of shield tunnel are considered in this method. Geometrical analysis is used to calculate the opening of joint, rotation of segmental lining and deformation of tunnel. Two laboratory segmental joint tests of full-scale shield tunnel with different axial loads are conducted to verify this method. Test results indicate that this method is efficient in sensing the deformation of shield tunnel. Furthermore, monitoring density of shield tunnel deformation can be significantly increased using this method. Using this long-distance, high-density, high-accuracy and low-cost healthy monitoring method, the safety of metro tunnel operation can be greatly ensured.