Research On Creep Behavior And Subgrade Engineering Application From Lake Sediments Soft Clay

The Creep is the main reason of the structures Sinking in soft-soil zone,high moisture content,high porosity and low permeability is contributed to the objective factors of creep.At home and abroad,many scientists do researchs on the soft-soil creep characteristics,based on laboratory test,numerical calculation and field monitoring.But because the soft soil in the way of material composition,origin,occurrence environment,should differences of stress history etc.,there id no one model can be summarized and applied in all regions.At the same time,it is also because the complexity and all kinds of soft soil region,this topic of the soft soil creep was always full of new life.Lacustrine soft soil is widely deposited in Central China and South China,having most distribution around the Yangtze River.Many tributaries meanders many diversions,the formation of the oxbow lake is also an important cause of deep soft soil deposits.With the development of economy and domestic basic construction,roads and railways to usher in a new boom.traffic network often need to pass these sedimentary soft soil area.Study on creep characteristics of lacustrine soft soil,accurate and effective evaluation calculation model,has important economic value and social significance for design and construction.Based on the national Hangzhou highway,Xiong Jia Zhen section of soft foundation section as the research area,creep characteristics and engineering application of soft soil.To reveal the different stacking height of embankment under sampling analysis,laboratory soil test,three axis creep tests on soft soil,creep settlement problem is studied,and obtained the following conclusions:（1）Soft clay on the physical characteristics of a series of experiments,experimental get along Town Lake sediments severe natural soft clay for 17.3kN/m3,Specific Gravity 2.71,natural moisture content of 49.5%,the saturated hydraulic conductivity of 2.13×10^-7 cm/s,X-ray diffraction analysis shows Gorges Reservoir lacustrine sedimentary soft clay particles to clay-based ingredients.（2）By triaxial creep test for the lacustrine sedimentary engineering properties of soft clay and mechanical parameters for testing,analysis lacustrine sedimentary soft clay shear creep test curves,strain-time,stress-strain curve when and pore water pressure-time curves discussed reservoir lacustrine sediments creep properties of soft clay:1)different confining pressures under different bias stress conditions,presents three kinds of soft clay creep characteristics:instantaneous elastic deformation,and attenuated creep and stable creep deformation.2)at very low bias stress conditions,sample instantaneous elastic deformation increases with time,creep deformation is small,negligible;3)in the middle stress conditions,instantaneous elastic deformation of the sample,then the occurrence of creep deformation creep strain rate decreases over quite a long time,and finally goes to zero,the creep curve was attenuated;4)at high bias stress conditions,a larger sample instantaneous elastic deformation and creep deformation,creep Variable rate gradually smaller and tends to a value greater than zero,the creep curve steady flow type;5)under the same conditions confining pressure,the greater the bias stress,the greater the elastic deformation,creep effect is more significant;6)same bias Under stress conditions,confining pressure,the smaller the elastic deformation,creep effects worse.（3）Summarizing Soft Soil Creep model theory and empirical creep theory,soft soil creep mechanism,based on this,constitutive model of soft clay to establish reservoir lakephase,to determine the model parameters of linear viscoelastic,linear viscoplastic model parameters and nonlinear viscoplastic model parameters.Gorges Reservoir lacustrine soft soil creep constitutive model and creep test curves were analyzed to establish the model parameters fewer,easier engineering applications.（4）Based on the calculation principle of FLAC^3D,analyze the nonlinear creep constitutive model constructed in this paper,for secondary development,and the establishment of model validation.Numerical results show that the strain curves and the interior fit and high soil test results,it proves that the establishment of the reservoir area lacustrine sediments rationality constitutive model of soft clay Program.（5）Taking a soft subgrade fill freeway segment,for example,is calculated using FLAC^3D preloading embankment settlement laws,combined with the stress distribution and soil lateral deformation of the space segment of the reasons to produce displacement analysis.Settlement amount of the target amount,the creep model parameter sensitivity analysis,and disposal program proposals.