Author(s): Takahiro Itoh, Takahisa Mizuyama, Michinobu Nonaka, Satoshi Tagata, Satoru Matsuda
Linked Author(s): Takahiro Itoh
Keywords: Debris flow, bed pressure, vibration, detection, LVP sensor
Abstract: A LVP sensor is consisted of load cell, acceleration meter and pressure meter, and some sensors can detect debris flows occurrences even if the other sensors are broken for continuous detections of debris flow. The flame of the sensor is made by stainless, the thickness of top plate (force plate) is 25 mm and the load is measured by a centered round plate with 60 mm in diameter. The small size of a force plate for load measurement is designed to avoid direct collisions due to boulders to the plate. The LVP sensor is better to use together with a wire sensor, and the sensor, which is modified several times, is installed on the bed at Nojiri No. 7 sabo dam on February 6th, 2015 in Sakurajima Island. There are several patterns of detections of debris flows such that the LVP sensor detected at almost same time to disconnected wires, the LVP sensor could detect several surges after disconnected wires and the LVP sensor could not detect perfectly because of transverse flow shifting. Referring to relationships between the flow depth and load, between the flow depth and vibration at the time of disconnected wires, there seem to be some threshold for debris flow event, though the sediment concentration could take various value for the flow depth. The threshold value for debris flow occurrences is estimated at 400 kgf/m2 in load and 200 mVolt in vibration, though more data collections are necessary. Supposing combination both a wire and LVP sensor, the data for debris flow detections were collected by the LVP sensor in every debris flow event, and the threshold value are tried to determine through continuous monitoring by the LVP sensor
Year: 2017