Feasibility of Leakage Detection in Diaphragm Walls Using OFDR-Based Fiber-Optic Temperature Sensing with Active Heating

Jianian Yang^*

• Suzhou Rail Transit Science and Technology Innovation Research Institute Co., Ltd., Suzhou 215100, China, Suzhou, China

Diaphragm walls are important subsurface retaining structures, and their cast quality is mainly influenced by geological conditions, construction methods, and equipment. Leakage stemming from defects in diaphragm walls is an intermittent yet critical issue that demands attention. To address the limitations of conventional inspection methods and devices — including difficulty in locating leaks in diaphragm walls, high detection cost, poor continuity, low immunity to interference, and limited timeliness — we propose a method for continuous detection of diaphragm-wall leakage using an active heat source combined with fully-distributed optical frequency-domain reflectometry (OFDR) temperature sensing. We designed and conducted indoor model tests, analyzed the characteristics of the temperature-rise curve during active heating and the accuracy of fiber-optic measurements, characterized the spatiotemporal distribution and evolution of temperature along leakage pathways and on exposed leakage surfaces at the leakage, accurately identified and located leaks, and preliminarily validated the feasibility of the method.