单向流条件下单桩桩周冲刷过程特征试验研究

水流引起桩基周围地基冲刷是海洋工程中的经典课题,由于问题涉及流体动力学和土力学的交叉内容,加之试验技术和计算能力的限制,这一冲刷过程仍有很多方面尚待进一步厘清。开展10组室内水槽试验,研究了不同水深情况下定床和动床冲刷时单桩桩周局部冲刷深度的发展过程。在试验过程中,通过模型桩内放置摄像机实时监测桩周冲刷深度变化,得到桩周冲深边界及最大和最小冲深方位随时间的变化曲线。试验研究发现这一冲刷过程主要特征为:局部冲刷首先发生在桩(侧)前方并逐渐向桩周扩展,而桩后则先发生淤积后再冲刷;水深越大,流速越大,桩后淤积现象持续时间越短,桩周冲刷发展迅速、均匀,但达到稳定所需时间越久;桩周最大、最小冲深点首先分别位于桩的侧前方、桩后区域,随着试验进行会发生转变或波动。

Scour characteristics at the periphery of a vertical pile under steady flow

Local scour around pile foundations is a classic issue in ocean engineering, which involves both the hydrodynamics and soil mechanics. With the current limitation of experimental techniques and computational capabilities, the scour process around the pile foundation is not clear and needs to be further explored. In this paper, ten flume experiments were conducted to study the development of local sour around a single pile under clear-water and live-bed conditions. During these experiments, a camera was placed inside the model pile to monitor the change of scour depth at the periphery of the pile, and then the curves of scour depth, maximum and minimum scour points over time were obtained. The test results illustrated the characteristics of local scour process: the local scour started in the zone in the side and front of the pile and then extended around the pile boundary. The sand at the back of model pile deposited first and then was washed away. When the water depth and the flow velocity were lager, the sand deposition at the back of model pile lasted shorter, and the local scour around the pile developed fast and needed longer time to reach the equilibrium state. The maximum point first appeared between the front and the side of the pile, and the minimum point was at the back, which changed or fluctuated during the scour process.