珊瑚砂振冲密实加固响应室内模型试验研究

Laboratory experiment study on response of vibroflotation compaction of coral sand

随着海洋岛礁工程的大力推进,吹填珊瑚砂地基的密实加固问题开始备受关注。利用自主研发的室内振冲器开展了珊瑚砂饱和砂土地基的室内振冲模型试验研究,深入分析了振冲过程中动孔隙水压力、水平动土压力等动参量的响应规律,探讨了振冲后沉降变形、相对密实度的变化特征。结果表明:松散珊瑚砂地基的密实度在经过两次双点振冲反复加固后均提升至中密。其中相对密实度在振冲点位处的提升效果较其余位置更为明显,并且中层或深层区域的加固效果优于表层区域。在超孔隙水压力方面,其最大值出现在振冲珊瑚砂地基过程中的贯入阶段,并且在留振开始时出现衰减现象。珊瑚砂地基在振冲器上拔过程中超孔隙水压力发生断崖式下跌。在第2次贯入时,超孔隙水压力比的峰值较首次出现显著下降。超孔隙水压力比等值线云图表明,振冲过程中的超孔隙水压力比等值线呈现平行分布。珊瑚砂浅层水平土压力随振冲器的贯入与拔出均呈现增加态势,深层水平土压力则呈现减少态势。

The treatment of the hydraulic fill coral sand ground starts to attracted a lot of attentions with the development of marine island reef engineering.By using self-developed laboratory vibroflotation instruments,vibroflotation tests on of saturated coral sands ground are conducted to analyze dynamic response regularity during vibro-compaction,such as dynamic pore water pressure and horizontal earth pressure.The characteristics of settlement and relative density are also investigated.The results indicate that loose coral sands can be improved to medium density after two times of double-point vibro-compaction;meanwhile,the most obvious effect to relative density appears at the point where vibrator works,and the middle or deeper areas are better improved than the surface areas.The maximal excess pore water pressure appears at the stage of vibrator penetration.The excess pore water pressure starts to attenuate at the beginning of vibration retention.A significant descend of excess pore water pressure happens when vibrator starts to lift.The peak excess pore water pressure of the second penetration is obviously smaller than that of first penetration.The excess pore water pressure ratio contours exhibits parallel distribution during vibro-compaction.The shallow horizontal earth pressure of coral sands shows an increase with both penetration and extraction of vibrator,while the deep horizontal earth pressure presents a decrease.