Development of an FBG-sensed miniature pressure transducer and its applications to geotechnical centrifuge modelling

Because of the elevated gravity and dimensional constraints, miniaturized sensors are required to measure pore pressure within soil specimens in geotechnical centrifuge testing. Electrical sensors have been used for the purpose. The small dimensions and their mechanical configurations made the available electrical pore pressure sensors fragile. They can be easily damaged in specimen preparation and testing. The electrical sensors tend to have a nonlinear and non-repeatable behavior in negative pressure range. Taking advantage of the optical fiber Bragg grating (FBG), the authors developed an FBG based miniature pore pressure sensor. The FBG sensors are immune to moisture and electromagnetic interference. The readings are linear in both positive and negative pressure range. A specially made FBG readout unit capable of taking readings at 10 kHz was used to monitor the pore pressure within the soil specimen in dynamic centrifuge tests. The paper describes and design of the miniature FBG pore pressure transducer system and its applications in static and dynamic physical model tests at the Cambridge University and National Central University geotechnical centrifugal testing facilities.