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土体在天然沉积过程中由于时间效应会产生次固结变形和结构性,两者都使土体的固结屈服压力增大,传统Bjerrum次固结模型无法解释后者的机理,也无法描述结构性土的次固结变形特性。通过天然沉积结构性土的次固结试验,基于Burland提出的孔隙指数Iv和固有压缩曲线ICL,分析了结构性土的次固结变形机理。当固结压力小于固结屈服压力时,天然沉积结构性土的结构强度抵抗了孔隙的压缩势,压缩曲线与固有压缩曲线间的距离△Iv随压力增大而增大,该阶段存在稳定的土颗粒骨架结构,土颗粒的蠕动变形受抵抗,导致几乎不产生次固结变形;而当土体处于临界屈服状态时,土结构强度受破坏,孔隙压缩势的抵抗作用消失,大孔隙骨架坍塌,Iv发生骤减,土颗粒的蠕动变形剧烈,次固结系数骤增出现峰值;△Iv随固结压力的进一步增大而减小,次固结系数的变化表现出与△Iv密切的线性相关性;基于天然沉积土SCL压缩曲线说明了天然沉积土的次固结变形不可能无限发展。
Both the secondary consolidation deformation and the structure of the soil due to the time effect in the natural sedimentation process will cause the consolidation yield stress of the soil to increase. The traditional Bjerrum secondary consolidation model can not explain the latter mechanism nor can it be described Secondary consolidation deformation of structural soil. Based on the secondary consolidation test of natural sedimentary structured soils, the secondary consolidation deformation mechanism of structured soils was analyzed based on the porosity index Iv proposed by Burland and the intrinsic compression curve ICL. When the consolidation pressure is less than the consolidation yield pressure, the structural strength of the natural sedimentary structured soil resists the compression potential of the pore, and the distance between the compression curve and the intrinsic compression curve, △ Iv, increases with the increase of the pressure. At this stage, the stable The creep deformation of soil particles is resisted, resulting in almost no secondary consolidation deformation. When the soil is in a critical yield state, the strength of soil structure is destroyed, the resistance of pore compression potential disappears, and the macropore framework collapses , Iv is abruptly decreased, and the creep deformation of soil particles is vigorous. The peak value of secondary consolidation coefficient increases sharply. △ Iv decreases with the increase of consolidation pressure. The secondary consolidation coefficient shows a close linear relationship with △ Iv Correlation; SCL compression curve of natural sediment shows that the secondary consolidation deformation of natural soils can not be infinitely developed.