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Takeuchi, Shinji; Kashiwai, Yoshio*; Hirata, Yoichi*; Yoshida, Yukimi*; Nishigaki, Makoto*
Proceedings of 4th IEEE/LEOS Workshop on Fibres and Optical Passive Components (WFOPC 2005), p.393 - 398, 2005/00
A multi-level groundwater monitoring system using FBG sensors has been developed for measuring pore water pressure and temperature in small diameter boreholes. The system consists of packer units, temperature and pressure sensing units, and optical fiber cable connecting units. The system with two measurement sections was established as a prototype for the feasibility study. A preliminary test was carried out for about 11 months in a borehole in the Tono area central Japan. The test data obtained in early period were unstable and periods of data loss occurred. Several improvements were implemented and subsequent results show the developed system is feasible for using in slim boreholes.
Hirata, Yoichi*; Yoshida, Yukimi*
JNC TJ7440 2005-085, 25 Pages, 2003/03
JNC-TJ7440-2005-085.PDF:2.49MB
Long-term monitoring system for the underground water is needed as one of the important method to understand characteristic of hydro-geology. To measure long-term pore water pressure, we manufactured the pore water pressure monitoring system with optical fiber sensors which have long term stability and durability, On this job, we producted a new type monitoring system which has two identified zone for measuring water pressure and temperature.This system is divided in two parts by the sense of installed place. The down-hole part is composed of the packer units, temperature and pressure measuring units and optical fiber jointing units. The surface part is composed of observation and data-saving equipment.The specification is as following* Measurement method: FBG (Fiber Bragg Grating)* Measurement contents: Pressure and Temperature* Range: 0-10 kgf/cm
(0-1MPa)* Accuracy: plus mimus 0.5%FS* Borehole diameter: from fai 86 to fai 100 millimeterThis system was installed at the DH-5 bore-hole.