瓯江河口巨厚海相软土沉积历史与工程特性

瓯江是浙江省内第2大河流，瓯江河口区是国内典型的软土分布区，曾经历过3次显著的海侵事件，其中尤以全新世海侵规模为大。但至今尚未开展过针对不同海侵软土的沉积历史及工程特性的系统对比研究。在研究各期海相软土层沉积历史与展布特征的基础上，对各层软土的物理力学性能进行了研究和对比分析，发现：随着地层由老到新，软土力学性能与结构性随之显著降低，土体灵敏度明显增强。物理力学指标的相互关系上，全新世软土的含水量与湿密度、压缩系数和孔隙比等指标间线性关系相对较好，而随着沉积历史的增长，土体指标间的线性关系不再显著，离散性增强。特别地，随着沉积时代的增长，土体的水平向渗透系数显著增长而垂向渗透性逐渐减少，两者之间相差可达10倍。

DEPOSITION HISTORY AND ENGINEERING CHARACTERISCS OF THE HUGE THICK SOFT SOIL IN OUJIANG ESTUARY

Oujiang is the second largest river in Zhejiang province, and Oujiang estuary is a typical area where soft soil is distributed in China. Oujiang estuary has experienced three transgressions in Quaternary Period, and three layers of soft soil was formed ever since. The transgression which happened in Holocene Epoch is the largest in scale, Yetthe deposition history and engineering characteristics of the three layers of soft soil formed duringtransgressions have not been compared or studied. On the basis of studying the deposition history and distribution characteristics of soft soils formed in different deposition stages, the physical and mechanical properties of the soft soil were studied and compered. It was found:as the stratum become newer, the physical properties and the struct of the soft soil become weaker, the sensitivity of the soil become more remarkable. In the relationship between physical and mechanical indexes, the water content of the silty soft soil which is formed in Holocene Epoch is in good linear relationship with wet density, compressibility coefficient and void ratio. As the deposition history extended, the linear relationship between indexes was no longer remarkable, the discreteness enhanced. Specially, as the deposition history extended, the horizontal permeability coefficient enhanced remarkably and the vertical permeability coefficient decreased gradually, the multiple can be up to 10 times.