Assessment of In Situ Scour Profile in Sand Using a Jet Probe

Abstract

Work in this paper presents a device and a process for in situ assessment of erosion potential with depth. The proposed device is termed “in situ erosion evaluation probe” (ISEEP), and the process is developed based upon advancing a rod fitted with a truncated cone jet nozzle into the soil. As water exits the nozzle with controllable velocity and flow rate (induced by an external pump) the probe advances into the subsurface profile and the rate of advancement is measured. The jet flow velocity and the advancement rate of the probe are correlated with a stream power value, and used to estimate soil erodibility parameters. Results from laboratory testing show the feasibility of the concept. An approach for the estimation of a critical stream power and a detachment rate coefficient is presented. Numerical modeling and deployment of the device at a North Carolina barrier island site after hurricane Irene are used to demonstrate the applicability of the proposed concept. Correlations between scour magnitudes, estimated by ISEEP parameters, and those estimated through modeling and field observation are presented and illustrate the viability of ISEEP’s soil erosion parameters as defined by a critical stream power and a detachment rate coefficient.

Assessment of Scour on Bridge Foundations by Means of in Situ Erosion Evaluation Probe

“…The viability of obtaining various penetration rates by using the probe with an increasing jet velocity is demonstrated in this work. Results also indicate that the probe is capable of applying various velocities with the same flow rate as well as various flow rates at the same velocity by changing the size of the jet orifice (8).…”

“…The test procedure follows that described by Gabr et al (8). To estimate the critical stream power (P c ) at two depths, the penetration rate is plotted against the natural log of the stream power, and extrapolation is performed to a zero penetration rate, as shown in Figure 3.…”