Abstract:

Based on the fiber Bragg grating (FBG) sensing system, heat pulse method is proposed for concentrated leakage monitoring in core rockfill dam. Model experiment was carried out with monitoring system composed of sensing-heating unit, regulated power supply, booster and FBG demodulator. At first, the aggregate was in dry and moist condition respectively. The experimental results show that it is difficult for temperature rise to make an exact identification to leakage state, so two dimensionless distinguishing indices ? and ? were defined; where ? was related to seepage velocity and ? was related to water table gradient. Then, two cases with various leakage flow rates were carried out and the leakage state was identified by ? and ? respectively. The results show that both ? and ? can locate the leakage position exactly and can reflect leakage intensity qualitatively. The identification effects by using ? as distinguishing index are better than ?

Key words: safety monitoring, heat pulse method, concentrated leakage, porous media, fiber Bragg grating sensor