Investigation of pore pressures during high-velocity impact by a free fall penetrometer

Free-fall penetrometers (FFPs) are an attractive tool for the rapid characterization of sediments in the nearshore and coastal areas. To improve their measurement capabilities, modern FFPs can be equipped with pore pressure sensors. Pore pressure measurements are extensively used in traditional cone penetration testing, but their usage and interpretation is still limited for FFP testing. This study represents an effort to advance the interpretation of pore pressure measurements from FFP testing.
Data was collected using the torpedo-shaped FFP BlueDrop during surveys at Herschel Island, YT, Yakutat, AK, Clay Bank, VA, and Yorktown, VA. Two major advancements regarding current data analysis of FFP pore pressure measurements were explored: 1) a method based on fluid dynamic principles was proposed to correct the pressure recordings for the dynamic flow effects due to the high-velocity fall and impact. The results show that using Bernoulli’s theorem coupled with the concept of pressure coefficients results in good agreement between measured and hydrostatic pressures during the free-fall and initial penetration stage. 2) Pore pressure dissipation curves measured by the penetrometer at rest at maximum penetration depth were also studied. The mechanisms behind the non-standard dissipation curves were explored. This dataset contains data that was used during this study and was collected during field surveys to the aforementioned sites.

自由落体贯入仪（Free-fall penetrometers，简称FFPs）作为一项快速表征近岸及海岸地区沉积物的工具，具有极大的吸引力。为提升其测量能力，现代FFPs可配备孔隙水压力传感器。孔隙水压力测量在传统的锥形贯入测试中得到了广泛应用，但在FFP测试中的应用及其解释仍较为局限。本研究旨在推进FFP测试中孔隙水压力测量的解释方法。研究数据采用鱼雷形FFP BlueDrop在赫舍尔岛（Herschel Island，YT）、雅库塔特（Yakutat，AK）、克莱银行（Clay Bank，VA）和约克敦（Yorktown，VA）等地进行的调查中收集。本研究针对当前FFP孔隙水压力数据分析方法，探索了两大主要进展：1）基于流体动力学原理的方法被提出，以校正高速坠落和冲击引起的动态流动效应对压力记录的影响。结果显示，运用伯努利定理并结合压力系数概念，在自由落体和初始贯入阶段，测量值与静水压力之间具有良好的一致性。2）研究还探讨了贯入仪在最大贯入深度静止时测量的孔隙水压力衰减曲线。对非标准衰减曲线背后的机制进行了深入研究。本数据集包含了在此次研究中使用并在现场调查中收集的数据。