Development and performance evaluation of a novel FBG-based sensor for measuring positive and negative pore water pressure in soil

• Published in: Geotechnical Aspects of Underground Construction in Soft Ground pp. 378 - 386
• Main Authors: Jing, J., Wang, T., Zhou, W.
• Format: Book Chapter
• Language: English
• Published: CRC Press 2024
• Edition: 1
• Subjects: elastic diaphragm; geotechnical engineering; femtosecond fiber Bragg grating; pore water pressure sensor
• ISBN: 9781032538129; 1032538163; 1032538120; 9781032538167
• DOI: 10.1201/9781003413790-45

Pore water pressure sensors are essential instruments for geotechnical testing in the development of underground spaces. We report on a high-sensitivity pore water pressure sensor, incorporating a femtosecond fiber Bragg grating (Fs-FBG) embedded in an elastic diaphragm. The FBG is axially fixed at the center hole of the elastic diaphragm and sealed on the other end to a rigid plate, forming the core sensing component. An additional FBG compensates for temperature cross-sensitivity effects. A mathematical theoretical model suitable for measuring both positive and negative pore water pressures was proposed and simulated. The simulation results demonstrate the sensor's pressure sensitivity under positive and negative pressure conditions as 33.8586 pm/kPa and 32.136 pm/kPa, respectively. Calibration tests under positive pressure indicate that the sensor's sensitivity within a range of 100 kPa is 21.403 pm/kPa, with excellent linearity and a linear fit coefficient of 0.999. This confirms the sensor's capability for effective pore pressure measurement in the complex environments of geotechnical engineering.