Research On Calculation Method Of Peat Soil Foundation Under Embankment In Dali Area Of Yunnan

Peat soil,a kind of special soft soil with high organic matter content,is widely distributed in China,especially in southwest China.It is inevitable to have peat soil foundation with the expansion of highway network in southwest China.As a special soft soil,peat soil has many characteristics of general soft soil,for instance,high water content,large pore ratio,high compressibility,obvious thixotropism and creep properties.However,the nature of peat is not exactly the same as the nature of soft soil,it often has higher moisture content and much higher secondary consolidation settlement,being dominant position in settlement.However,at present,has not formed a set of applicable calculation methods in the calculation of peat soil foundation settlement at home and abroad.In the light of the foregoing,in combination of the peat soil foundation in Dali area of Yunnan Province,based on laboratory model test,numerical analysis and theoretical analysis,this paper studies the engineering properties of peat soil,settlement law and calculation method of peat soil foundation.The main findings are as follows:1.Referring to the physical and mechanical properties of mucky soil,peaty soil and peat undisturbed soil,with requirements based on similarity theory,this paper studies the similar materials for the model test.The similarity degree is evaluated by fuzzy comprehensive evaluation method to determine the model soil similarity material and to lay the foundation of the model test.2.This paper studies physical and chemical properties and compressive properties of three groups of model soils,whose test results are compared with those of undisturbed soil.It is proved that the model soil used in this model test can reflect the settlement law of the undisturbed soil.3.The experimental results of three groups of models are analyzed in detail.And then to build the test correspondence model with PLAXIS software,based on which the settlement law of peat soil foundation is studied in combination of the results of indoor routine test,indoor model test as well as numerical analysis.The key position of secondary consolidation of peat soil foundation in settlement is further explained,which is helpful for the calculation of settlement of peat soil foundation.4.With comparison and analysis of common settlement calculation results,it is confirmed that the main error in the calculation of peat soil foundation settlement is rooted in the calculation of secondary consolidation.On this basis,some secondary consolidation analysis of silt and muddy soil is used to predict the secondary consolidation of peat soil.The predicted results are compared with those of the model test so as to obtain a modified method for effectively predicting the settlement of peat soil foundation.