超软土的界定与特性

Definition and Characteristics of Ultra Soft Clay

文章推荐了一个适合于我国土质情况的超软土界定标准，在此基础上试验研究了超软土的工程特性。结果表明．我国沿海地区超软土黏粒含量为40％。50％，其中胶粒含量为30％～45％，蒙脱石含量为3．58％～19．58％：土粒双电层结合水层厚，黏土蜂窝状构造的凝聚体较大，吸水量多。泥浆的落淤沉积过程可分为两个阶段。第一阶段的絮凝沉积在2d内结束，第二阶段的沉降速率要慢很多。超软土固结变形在200kPa处出现转折点，转折点前呈大变形特征，转折点后变形速率变缓。超软土的固结特性和规律与地基的上层软土或黏土基本一致，当压力大于先期固结压力时．固结系数随压力的递增而递增。文章最后解释了超软土经排水固结加固后强度仍然较低的原因．

A definition criterion of ultra soft clay suitable for the soils in China is recommended for reference. The experimental research on the engineering characteristics of the ultra soft clay is conducted. The research shows that the clay grain content of the ultra soft clay in China littoral is 40% ~ 50%, its colloid fraction is 30% ~ 45% and montmorillonite fraction is 3.58% ~ 19.58%; thickness of bound water covering electric double layers of soil grain, coagulate of clay honeycomb structure and water absorption rate are relatively big. The course of slurry deposition includes two phases: the flocculent deposition in the first phase ends within 2 d, but the deposition in the second phase is much more slowly. consolidation deformation of the ultra soft clay has a turning point at 200 kPa, and big deformation appearing before it and slow deformation appearing after it. The consolidation characteristics and rule of the ultra soft clay are basically as the same as that of upper layer soft clay or clay of foundation, consolidation coefficient increases with pressure increase as the pressure is big than the pre-consolidation pressure. At last, the reason of lower drained consolidated strength of the ultra soft clay is explained.