Signal response of the Swiss plate geophone monitoring system impacted by bedload particles with different transport modes

Abstract

Abstract. Controlled experiments were performed to investigate the acoustic signal response of the Swiss plate geophone (SPG) system impacted by bedload particles varying in size, impact angle and transport mode. The impacts of bedload particles moving by saltation, rolling, and sliding were determined by analyzing the experimental videos and corresponding vibration signals. For a particle impact on the bed or on the geophone plates, the signature of the generated signal in terms of maximum amplitude, number of impulses and centroid frequency was extracted from the raw monitoring data. So-called signal packets were determined by performing a Hilbert transform of the raw signal. The number of packets was calculated for each transport mode and for each particle size class, with sizes ranging from 28.1 mm to 171.5 mm. The results show how the number of signal impulses per particle mass, the amplitude of the signal envelope, and the centroid frequency change with increasing particle size, and they also demonstrate the effect of bedload transport mode on the signal response of the SPG system. We found that there is a general increase in the strength of the signal response or in the centroid frequency when the transport mode changes from sliding to rolling to saltation. The findings of this study help to better understand the signal response of the SPG system for different bedload transport modes, and may also contribute to an improvement of the procedure to determine bedload particle size from the SPG signal.

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

“…A decrease in with increasing particle size was observed for different bedload surrogate monitoring techniques (Belleudy et al, 2010;Uher and Benes, 2012;Barrière et al, 2015). Furthermore, has the advantage of showing weaker dependency on the flow velocity and transport mode than the maximum registered packet amplitude (Wyss et al 2016b;Chen et al, 2021). As shown by Nicollier et al (2021b), also contains information about the impact location of a packettriggering particle.…”

“…increases together with the transport rate, with the transport of large particles (which typically generate packets of longer durations), and with the occurrence of sliding and rolling particles (Chen et al, 2021). The long packets take the place of multiple shorter packets that would otherwise be individually counted; thus, they lead to underestimated mass fluxes for a given value.…”

“…Numerous studies have reported successful calibration of impact plate systems in laboratory flumes (e.g. Bogen and Møen, 2003;Krein et al, 2008;Tsakiris et al, 2014;Mao et al, 2016;Wyss et al, 2016b,c;Kuhnle et al, 2017;Chen et al, 2021), although transferring these flume-based calibrations to the field remains challenging. Nonetheless, controlled flume experiments are valuable because they allow us to systematically explore relationships between the recorded signal, the transport rates of different sediment size fractions, and the hydraulic conditions.…”

Toward a general calibration of the Swiss plate geophone system for fractional bedload transport

“…A decrease in f centroid with increasing particle size was observed for different bedload surrogate monitoring techniques (Belleudy et al, 2010;Uher and Benes, 2012;Barrière et al, 2015). Furthermore, f centroid has the advantage of showing weaker dependency on the flow velocity and transport mode than the maximum registered packet amplitude (Wyss et al 2016b;Chen et al, 2022). As shown by Nicollier et al (2022), f centroid also contains information about the impact location of a packet-triggering particle.…”

“…Numerous studies have reported successful calibration of impact plate systems in laboratory flumes (e.g., Bogen and Møen, 2003;Krein et al, 2008;Tsakiris et al, 2014;Mao et al, 2016;Wyss et al, 2016b, c;Kuhnle et al, 2017;Chen et al, 2022), although transferring these flume-based calibrations to the field remains challenging. Nonetheless, flume experiments are valuable because they allow systematically exploring relationships between the recorded signal, the transport rates of different sediment size fractions, and the hydraulic conditions.…”