基于光纤传感的盾构输水隧洞内压加载原位试验研究

In-situ Experimental Study on the Behavior of Water Conveyance Tunnel Under High Internal Pressure Using Fiber Optic Sensing Technique

高水压作用下水工隧洞衬砌结构的承载特性及破坏机理复杂,借助现有的监测技术难以准确评价其工作状态.针对珠江三角洲水资源配置工程,开展了以“外衬管片-自密实混凝土-内衬钢管”叠合衬砌结构为研究对象的现场原位试验.采用分布式光纤感测技术对内压加载过程中叠合衬砌结构力学性能特征进行了深入探究.试验结果表明:在内压逐步增加的条件下,隧洞衬砌的应变发展呈现非连续阶跃的特征;内衬钢管环向应变起伏变化均匀、平缓,整体基本处于弹性工作状态;衬砌结构中的自密实混凝土在内压作用下由弹性变形进入弹塑性变形状态,且在管片拼接缝位置处出现裂缝;外衬管片在均布内压作用下呈现非均匀性的膨胀变形,且管片接缝张开显著区域主要分布于隧洞拱顶位置.研究结果从应变演化的角度揭示了叠合衬砌结构承载特性及破坏机理,充分验证了分布式光纤感测技术在输水隧洞结构健康监测中的巨大应用潜力.

The deformation behaviors of water conveyance tunnels under high internal pressure can scarcely ever be accurately evaluated using existing monitoring technologies.A full-scale experimental test,based on the project of water resources allocation in Pearl River Delta,was conducted to investigate the deformation mechanism of the superimposed linings consisting of a concrete segment,self-compacted concrete,and steel tube.The distributed fiber optic sensing was used to monitor the performance of superimposed linings under high internal pressure.The test results show that the strain development of the linings presents the character of discontinuous variation during loading.The steel tube generates elastic deformation,and the strain change is small.The deformation process of self-compacted concrete can be divided into two stages:elastic deformation and plastic deformation.The plastic zone gradually expanded from the concrete surface to the deep layers forming several cracks at the segment splicing joint.The spaces between some segments on the crown of the tunnel are prone to enlarge under high uniform internal pressure.The deformation characteristics and failure patterns of the superimposed linings were revealed in the view of strain measurement.This study verifies the great application potential of distributed fiber optic sensing in the water conveyance tunnel.