基于FRP筋自感知监测技术的隧道衬砌施工全过程应变分析

Strain analysis of tunnel lining during construction based on self-sensing monitoring technology of FRP

作为地下结构,隧道衬砌的隐蔽性导致其全天候的实时监测非常困难。提出了一种基于内嵌光纤自感知纤维增强复合塑料(fiber reinforced plastic,FRP)筋的隧道衬砌智能监测方法,将光纤传感器嵌入FRP材料中形成自感知FRP筋并嵌入隧道衬砌中,实现对隧道衬砌不同位置全天候、长时间、高精度监测,监测结果能够定量给出隧道衬砌环向的实时受力状态,反映裂缝生成风险。采用该智能监测方法对广汕高铁陈塘隧道进行了监测,监测数据反映了隧道衬砌施工全过程的力学机制。影响衬砌结构安全的因素主要有隧道围岩压力、水化热导致的温差应力以及混凝土干缩导致的应力;其中,混凝土水化热产生的温差效应导致衬砌内侧受到较大拉应力,需采取合理的施工措施以避免温差效应引起的拉应力过大而产生温度裂缝。所提出的智能监测方法能够全天候、长时间、实时监测隧道衬砌应力-应变状态,此自感知系统将在隧道运营过程中持续、及时反映隧道衬砌开裂风险,为高速铁路列车的运行安全提供技术保障。

It is difficult to monitor the underground tunnel lining in an all-weather manner due to its concealment. An intelligent monitoring method of tunnel lining based on self-sensing FRP(fiber reinforced plastic) bar embedded with optical fiber is proposed in this paper. The optical fiber sensor is embedded in the fiber reinforced plastic to form self-sensing FRP bar, which is installed in the tunnel lining, to monitor the stress state of the tunnel lining in a real-time and all-weather manner. The monitoring results can show the circumferential stress of the tunnel lining and predict the risk of crack generation. The intelligent monitoring method is used to monitor Chentang tunnel in Guangzhou-to-Shantou high-speed railway. The main factors affecting the safety of lining structure during the period from lining construction to operation are surrounding rock pressure, temperature difference stress caused by hydration heat and stress caused by concrete drying shrinkage. The temperature difference stress caused by hydration heat can lead to a large tensile stress on the inner side of the lining. Therefore, reasonable construction measures need to adopt to avoid cracking caused by temperature effect. The proposed intelligent monitoring method is capable of monitoring the tunnel lining stress-strain state in real time, for a long period of time and in all weather. This self-sensing system will continuously and timely reflect the risk of tunnel lining cracking during the tunnel operation, providing a technical guarantee for the operational safety of high-speed railroad trains.