| Dongting Lake area has a wide range of lacustrine sedimentary soft soil,which has the characteristics of strong compressibility,high natural water content,low strength and poor engineering properties,besides,it shows obvious creep characteristics compared with the general cohesive soil.When the soft soil layer is selected as the foundation,it is easy to have large settlement or uneven settlement with the increase of the upper load.If it is not handled properly,serious consequences such as house cracking,pavement collapse,abutment dislocation and so on may occur,resulting in huge economic losses.Therefore,it is of great significance to accurately predict and analyze the deformation of soft soil foundation and study its improvement characteristics for the treatment of soft soil foundation and the prevention of post construction settlement in engineering application.For this purpose,during the research period,this paper selected the soft soil of Dongting Lake as the research object,carried out one-dimensional consolidation creep research,studied the secondary consolidation law of soft soil,constructed the creep analysis model of soft soil,improved the soft soil with cement,explored the creep deformation mechanism of soft soil,and provided theoretical guidance for engineering application.The main research contents and results are as follows:（1）Indoor geotechnical tests were carried out to analyze the physical and mechanical indexes of structural soft soil in Dongting Lake District;At the same time,one-dimensional consolidation creep study was carried out to study the deformation characteristics of secondary consolidation,analyze the variation characteristics of secondary consolidation coefficient with consolidation pressure,and study the relationship between secondary consolidation coefficient and compression index.（2）Based on the results of one-dimensional consolidation creep study,the relationship between strain and time and strain and stress was determined.Based on the exponential Singh-Mitchell creep model,the relationship between model parameters and consolidation pressure was established,and an empirical model suitable for describing the creep characteristics of soft soil in Dongting Lake area was established.It is compared with Burgers creep model,Merchant model and Nishihara model to verify the applicability of the proposed model.（3）One-dimensional consolidation creep tests were carried out on cement samples with different cement incorporation ratios to analyze the influence of cement incorporation ratio on the deformation characteristics of soft soil in secondary consolidation,and to study its influence on the completion time of soft soil in primary consolidation;The variation characteristics of the secondary consolidation coefficient with the consolidation pressure are analyzed and the relationship between the secondary consolidation coefficient and compression index is studied.At the same time,the content of adsorbed bound water in soil-cement was measured by volumetric flask method,and the relationship between the content and cement incorporation ratio was studied to reveal the influence mechanism of cement on the secondary consolidation characteristics of soft soil.（4）The soft soil samples of simulated cement mixing pile composite foundation with different area displacement rates were prepared to carry out one-dimensional consolidation creep tests.The influence of cement mixing pile on the deformation characteristics of secondary consolidation of soft soil was analyzed,and the influence of cement mixing pile on the completion time of primary consolidation of soft soil was studied.The variation characteristics of the secondary consolidation coefficient with the consolidation pressure are analyzed and the relationship between the secondary consolidation coefficient and compression index is studied.Corresponding suggestions are put forward according to the problems existing in engineering application design. |
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