Monitoring Settling and Consolidation of Fluid Mud in a Laboratory Using Ultrasonic Measurements

Abstract

Ultrasound measurements are routinely used to evaluate the safe depth for ships navigationnautical depth -at waterways and ports using single-beam dual-frequency echo-sounders. The nautical depth is routinely defined by suspension density in the range of 1100-1300 kg/m3 in the mud layer. While ultrasound measurements have a weak sensitivity to density variations, calibration is always needed to convert ultrasound measurements into reliable indicators for nautical depth levels in the mud layers using densely distributed density rheological in-situ measurements.We present a laboratory ultrasonic transmission experiment to monitor the fluid mud's settling and consolidation processes using a sample from the Port of Rotterdam. We use P-and S-wave ultrasonic transducers in the frequency range between 200 to 1000 kHz. Our results show that the P-wave velocities slightly increase during the consolidation and settling process while the P-wave amplitudes decrease. On the other hand, we observe a high S-wave velocity that increases together with amplitudes over time. The P-and S-wave amplitude and S-wave velocity variation over time correlate well with the mud average density variation. The presented results can be very useful for fluid-mud monitoring at a lab scale, besides possible utilization for large-scale monitoring field campaigns.

Continuous monitoring of the depth of the water-mud interface using distributed acoustic sensing

“…If one could monitor the depth at these locations on demand, the availability of these docks would increase. Fadel et al (2021) and Ma et al (2021) showed that nonintrusive seismic measurements can be used for estimating shear strength in fluid mud.…”