| The selection of soil constitutive model was closely linked to the calculationaccuracy of the geotechnical engineering, so many scholars want to study it. With theconcept of half strength index, traditional Duncan-Chang model formula wasindicated that the mathematical defects of characteristic equation independent in thepaper. In order to overcome the defects, introduce the control convergence factor θand propose the improved Duncan-Chang model who was named prolongation modelbased on traditional Duncan-Chang model. Mathematical analysis stress-strainexpression of prolongation model and compare different control convergence factorof prolongation model with the stress-strain curve of Duncan-Chang model, it couldget the following conclusions: the prolongation model when the value of θ wasGreater than one and Duncan-Chang model had the same mathematical nature;Duncan-Chang model was one exception to prolongation model when the value of θwas equal to two; in the case of the initial tangent modulus and the limiting partialstress were determined, the prolongation model could simulate convergence rategreater than or less than the stress-strain curve of Duncan-Chang model by adjustingthe control convergence factor, but Duncan-Chang model could not achieve this effect;the control convergence factor of prolongation model was negatively correlated withthe convergence rate of stress-strain curve.In order to explore the solving method for prolongation model parameters,combine lsqcurvefit regression function of Matlab software with the least squaresregressive analysis to build the expectation function program about prolongationmodel multiple regression, Duncan-Chang model multiple regression and controlconvergence factor regression of prolongation model. Solve and compare the residualsum of squares with the above three kinds of regression base on the marine soft soilconventional triaxial test data. The study showed that the prolongation model multipleregression fitting the best and the Duncan-Chang model multiple regression fitting theworst. So the least squares regression method could be used as solving method forprolongation model parameters.To determine the finite element calculation parameters was the prerequisite for the use of finite element program. It used the control variable method to analyse themarine soft soil with the different confining pressure, at last, determine the best soilsample grid nodes were11*21nodes, the best height of sample cap was4units, thebest poisson ratio parameter of sample cap was0.3. Compare the Duncan-Changmodel simulation curve、the prolongation model simulation curve、the Duncan-Changmodel formula curve and the test data, it could prove that this finite element programwas feasible and the simulative effect of prolongation model was better than theDuncan-Chang model.In order to observe control convergence factor that impacted on the displacement,the stress, the strain, the safety and the swell-shrink characteristic of soil sample gridnodes, as obtaining the displacement contour maps, the deformation maps, thedisplacement vector maps, the stress contour maps and the strain contour maps of soilsample grid nodes of Duncan-Chang model and prolongation model, it couldsummarize that the control convergence factor had little effect on the radialdisplacement, the axial displacement, the radial stress and the axial strain of the soilsample grid nodes, but it was negatively correlated with the axial stress of the soilsample grid units. The control convergence factor was also negatively correlated withthe radial srtain of the soil sample central units, but it had little effect on the radialsrtain of the soil sample upper and lower units. Observe the minimum safety factorcontour maps and the curve about volumetric strain and axial strain of the two models,it could obtain that, the smaller the control convergence factor, the smaller theminimum safety factor of the partial units, the higher the security, and the shearshrinkage phenomenon was also more obvious. |
PDF Full Text Request