软基路堤拓宽静压PHC管桩挤土效应现场试验

PHC（prestressed high-strength concrete）管桩近年来被广泛应用。PHC管桩为挤土沉桩模式，沉桩过程引起的挤土效应对周围环境产生不利影响并对其可打性和承载特性有重要影响。结合广－清（广州至清远）高速公路扩建工程，通过现场监测超静孔隙水压力和土体水平位移，进行PHC管桩挤土效应研究。水平位移利用固定式测斜仪测量，孔隙水压力使用振弦式孔压计测量，并使用自动系统进行数据采集。研究发现，沉桩过程中引起的超静孔隙水压力变化随深度增加近似呈线性增长，水平方向随距离的增加而减小；挤土效应产生的土体水平位移随距离的增大而减小，随深度增加而减小；挤土效应滞后现象明显，可导致成桩后的桩体倾斜；拓宽地基场地上管桩施工对老路地基影响小，场地条件对沉桩挤土效应影响大，老路路堤对垂直于路基方向的水平位移有约束作用。

Field test on extruding soil caused of PHC pipe pile driving by static pressure for improving soft foundation of widened embankment

PHC pipe pile is widely used in recent years. The application of PHC pipe pile belongs to soil compaction pile-sinking mode. The compaction effect caused during piles driving would produce adversely effects on the surrounding environment and affects its possibility and bearing characteristics. The study of compaction effect was conducted based on the measurements and statistics of excess pore water pressure and horizontal displacement in the Guang-Qing Expressway Expansion Project. Horizontal displacements were monitored by fixed inclinometer measurements, pore water pressure was measured using vibrating wire, and using the automatic data acquisition system of data acquisition. The studies show that excess pore water pressure which caused by pile-driving in the project presented approximately linearly with the depth increasing and reduced with the distance increasing in the horizontal direction. Soil horizontal displacement of soil compaction effects decreasing as the distance increasing; it also has the significantly of hysteresis which can lead to pile body tilt. Piling on the widened foundation influences the original foundation slightly, while the site conditions have remarkable impaction on pile driving effect. The old embankment restraints horizontal displacement perpendicular to the roadbed direction.