The riverbank collapse poses a serious threat to the safety of urban areas and critical infra-structures along the Yangtze River.At present,the commonly used monitoring techniques expose some problems,such as limited parameters and low monitoring frequency.To improve the effectiveness of river-bank collapse monitoring and early warning,a real-time monitoring approach based on weak fiber Bragg grating(WFBG)technology is introduced.This method employs weak fiber brag grating sensors as meas-uring units,and then utilizes time-division/wavelength-division hybrid multiplexing demodulation tech-niques together with some relevant conversion formulas to distinguish groundwater flow velocities under active heat source.A real-time monitoring system of riverbank collapse site can be set up for collecting multiple parameters simultaneously,including strain,temperature,displacement,flow velocity,and so on.We analyzed the monitoring data of WD02 borehole,which was located at the Zhinan Village riverbank collapse site in Yangzhong City.The results showed that there were two abnormal flow velocity zones at the depth of 20～30 m and 62～80 m,where the follow velocities reached 2.98×10-6 m/s and 3.4×10-6 m/s,respectively,nearly twice of the values observed in adjacent layers.Consequently,it is necessary to pay more attention to these two abnormal zones.Typical practice case shows that this technology has the advantages of accurate positioning,abundant data collecting and real-time monitoring even under extreme weather conditions.This research provides a cutting-edge and reliable alternative solution for the monito-ring and early warning of riverbank collapse disasters.
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