Disturbed State Model Of Soft Soil And Verification

Soft soil distributes abroad in Zhujiang Delta area. The maincontent of soft soil is silt, muddy silt and clay. The soft soil hascharacteristics such as high water content, high compressibility,low strength, high sensitivity and thixotropy. With the rapiddevelopment of area economy, more and more large and giantprojects are built, which leads to stricter and newer requirements ondeformation and stabilization. The key to settle these problems is toestablish suitable geotechnical mechanical constitutive models.Geotechnical constitutive models are the gist to analyze thedeformation and stabilization of rock and soil. The exactitude ofconstitutive equation directly influences the accuracy of evaluationand analysis in rock and soil deformation and stability, and itdirectly relates to the input and success-fail of the project. So it issignificant to study geotechnical constitutive models.In view of what mentioned above, combining with originalityinnovation foundation of Jilin University-"Study on disturbed stateconstitutive model of soft soil", using soft soil in Zhujiang Deltaarea as investigated subject, the paper studied the structuralproperty of soft soil. Based on the laboratory test and fieldengineering, the paper introduces disturbed state concept andverifies the exactitude of the model, ordering to establish aconstitutive model which can reflect the structure of soft soil.The experimental study on the property of soft soil inZhujiang Delta area has been performed, the results show that:â‘ The curves of compressibility are distinctively different betweenundisturbed sample and reconstituted sample in one-dimensionalcompression test. The compression curve of undisturbed sample ine-p co-ordinates is relatively flat at the beginning, with the loadincreasing curve appears evident inflection point and the decrementis increased significantly, it is different from the compression curveof reconstituted sample. â‘¡ When the pressure is less thanstructural yield stress, the value of consolidation coefficient ofundisturbed sample is high and for one fundamental constants.When the pressure convergence structural yield stress, theconsolidation coefficient become small rapidly. With increasedpressure consolidation coefficient small changes, in the plan tohave the line basically, and the value is small relatively. â‘¢Soft soilhas structural strength obviously. According to conventionalmethod of preconsolidation pressure solve, the solved pressure isnot true preconsolidation pressure of structural soil, and it isstructural yield pressure, which is sum of preconsolidation pressureand structural strength.Next, disturbed state concept is introduced. The basic idea ofdisturbed state concept lies in that actual deformation aresuperposed of two parts, material deformation of relative intactstate and fully adjusted state. Fully adjusted state is considered asreconstituted state while relative intact state as ideal rigid material.Adopting ideal compression curve of structural soft soil andreconstituted soil put forward by Martin D Liu and John P Carter ofSydney University, considering the structural yielding stress, thepaper improves the model expression. Using the soft soil samplesfrom Zhuhai, Nansha and Shenzhen, through compression test, thepaper verify the model.Finally, considering that consolidation coefficient is not aconstant in the course of consolidation, the paper deduces theexpression of consolidation coefficient as consolidation pressurevarying, according to stress-strain relationship of disturbed statecompression model. In the settlement calculation, considering thevariation of consolidation coefficient and the condition of stageloading, the paper simplify the model as piecewise function and usereal monitoring settlement data of surcharge preloading treatmentsoft foundation in Shenzhen to verify the model further.