CARUSO, CARY WAYNE. In Situ Measurement of the Scour Potential of non-cohesive Sediments (ISEP). (Under the direction of Dr. Mohammed A. Gabr.) A vertical probe (VP) employing a water jet has been developed for assessing the scour potential and scour rates of sediments. The probe termed "In situ Scour Evaluation Probe," or ISEP, is based on the idea by Dr. Gabr that analysis of the probe penetration rate into the soil may be correlated with scour rate and erosion potential. This method measures the potential scour rate in situ and as a function of depth. Work in this thesis describes the applicability and the laboratory-based experimental verification of the ISEP and provides insights into the effects of the water jet parameters (i.e. water volume flow rate and jet nozzle velocity) on maximum probe penetration depth, the probe insertion rate, and the estimated erosion rate. In addition, ISEP is applied in the field at two sites for validation of the testing approach. Results on the test sand with mean particle diameter (D 50) ~0.3 mm suggest that the maximum depth of advancement of the probe can be empirically correlated to the vertical velocity of the water at the tip of the probe raised to a positive exponent. The rate of probe advancement also seems to vary with moisture content. Thus far, scour rates determined with this method are comparable with published scour rates for similar sand type. results are presented from field trials showing the ISEP can differentiate between eroded and replaced sands of the Isabel breach and the non-eroded sands of the outer banks Erosion rate and velocity are also related to the depth of the probe as well as tip water velocity for the sand in the test pit. A relationship between erosion rate and depth is presented for the sand in the test pit. The relationship between erosion rate and depth suggests that effective stress and friction are major factors controlling erosion rate with depth. Application of this technique to different sands in the Isabel Breach on the outer banks of NC shows that this technique has the ability to differentiate between reclaimed sands and uneroded sands. More specifically, erodibility values for the reclaimed sands in the breach area average between 4 and 5 times larger that the erodibility values for the uneroded sands outside of the breach. In addition, the shape of the erosion rate versus depth curves in the breached zone is different from the shape of the curve in the unbreached zone. Results are also presented for sands in two other field trials and are consistent with previous results.
