Research On Consolidation And Secondary Consolidation Of Soft Soil Under K₀Lateral Constraint

The deformation and long-term deformation of dredger fill has always been ahotspot in academic and engineering. Structures built on reclaimed land foundationwill produce a great settlement, especially the influence for later application coursedby post-construction settlement. Thus the accurate calculation and forecast of thesettlement has great meaning for practical engineering. As the main reason for thelong-term deformation of soil and long-term settlement of soft soil foundation, thestudy of secondary consolidation deformation is necessary for the after constructiondeformation control.In this article, the confined compression refers to the soil consolidation with notallowing of the lateral deformation. K₀consolidation refers to geometric consolidationwhich the ratio of the vertical stress and lateral stress is exactly equal to an estimatedvalue of K₀.The engineering practices show that the consolidation state of deep softsoil is more inclined to K₀consolidation and the real situation of the lateraldeformation cannot be reflected via the confined compression test. Based on theprinciple of consolidation test, using the soil from the reclaimed land foundation ofShantou （Guangdong province）, a long-term deformation test of using confinedcompression and K₀consolidation respectively is presented in this paper. Animprovement of K₀consolidation apparatus is performed to meet the experimentalrequirement. A result comparison between the confined compression test and K₀consolidation test is proposed, a research on the characteristics of consolidation andsecondary consolidation deformation through the two tests is proposed as well. Inaddition, the change law of K₀with time is obtained through the study on K₀in theprocess of confined compression.Through to the test results, the main conclusions are as follows:1. Confined compression and K₀consolidation are influenced by soil structure.Coefficient of secondary consolidation and compression modulus change greatlywhen consolidation reach the preconsolidation pressure. 2. Compared with confined compression, K₀consolidation has significantinstantaneous deformation which affects the soil consolidation and secondaryconsolidation and makes the secondary consolidation coefficient and compressiondeformation in K₀consolidation less than in confined compression. Moreover, theprimary consolidation of K₀consolidation finishes faster and the dividing point ofprimary-secondary consolidation in K₀consolidation happens in advance.3. K₀in confined compression process is not a constant, which reaches maximumvalue after loading then gradually decreases and tends to stable.4. Based on elastic mechanics, Terzaghi’s one-dimensional consolidation theory isimproved, the curves of Uzt-Tvat different K₀are obtained. According to thecurves of Uzt-Tv, the smaller is K₀, the faster consolidation completed. When K₀is0.67, the curve of Uzt-Tvis the analytic solution of Terzaghi’s one-dimensionalconsolidation theory.