Vertical pore pressure variations and geotechnical sediment properties at a sandy beach
Vertical pore pressure variations and geotechnical sediment properties at a sandy beach
复制标题
DOI：
10.1016/j.coastaleng.2021.104058
复制
发表时间：
2021-11
影响因子：
4.4
通讯作者：
N. Stark;P. Mewis;Bridgit Reeve;M. Florence;Jan Piller;J. Simon
中科院分区：
文献类型：
--
作者：
N. Stark;P. Mewis;Bridgit Reeve;M. Florence;Jan Piller;J. Simon
岩土工程性质和土壤特性对海滩动力学的作用以前已经被认识到，但是在充满活力的海滩环境中的岩土工程现场测量仍然很少。这项研究的重点是两天的实地测量沿着一个跨海岸的横断面，从沙丘的脚到达上潮下带在西桑迪海滩的叙尔特岛，德国，南部的城市韦斯特兰。沉积物特性和岩土参数是从沉积物取样和有限的现场测试中获得的。孔隙压力测量进行了沿着垂直阵列在上55厘米的海滩表面在下潮间带。然后使用基于毕奥（1956）和梅和福达（1981）的一维垂直（1DV）模型分析孔隙压力记录。实验室测试结果表明，从陆上到潮间带下部，粒度和摩擦角略有增加的趋势。使用便携式自由落体重力仪进行的现场沉积物强度测试支持陆上和潮间带摩擦角的趋势。此外，一个显着增加的沉积阻力，观察到在冲带和上潮下带。孔隙压力记录显示出一致的趋势与潮汐水海拔。然而，在低潮期间收集的数据表明，地表水的影响和地下水的脱钩，可能与气体含量和负孔隙压力在渗流区。孔隙压力记录还表明，在上部沉积层和一个小的相位滞后波阻尼更明显。1DV孔隙压力模型成功地模拟了所有沉积物深度的观测压力，并建议在测量期间没有液化事件，但可能影响沉积物动力学的有效重量减少。
The role of geotechnical properties and soil behavior for beach dynamics has been recognized before, but geotechnical field measurements in energetic beach environments are still rare. This study focused on two days of field measurements along a cross-shore transect reaching from the foot of the dunes to the upper subtidal zone at the western sandy beach of the island of Sylt, Germany, just south of the city of Westerland. Sediment properties and geotechnical parameters were obtained from sediment sampling and limited in-situ testing. Pore pressure measurements were conducted along a vertical array in the upper 55 cm of the beach surface in the lower intertidal zone. Pore pressure recordings were then analyzed using a one-dimensional-vertical (1DV) model based on Biot (1956) and Mei and Foda (1981). Laboratory testing results demonstrated slight trends of increasing grain size and friction angles from the subaerial to the lower intertidal zone. In-situ sediment strength testing using a portable free fall penetrometer supported the trends in friction angles for the subaerial and intertidal zone. Additionally, a significant increase in sediment resistance was observed in the swash zone and upper subtidal zone. Pore pressure recordings showed a consistent trend associated with the tidal water elevations. However, data collected during low tide suggested a decoupling of surface water effects and groundwater, possibly associated with gas content and negative pore pressures in the vadose zone. Pore pressure recordings also suggested a more pronounced wave damping in the upper sediment layers and a minor phase lag. The 1DV pore pressure model succeeded to simulate the observed pressures at all sediment depths well, and suggested no liquefaction events during the measurement period, but a reduction of effective weight that may affect sediment dynamics.