Numerical Simulation For Widening Embankment On Soft Ground Improved By Plastic Drainage Plates And Djm Piles

In recent years,with the development of economic construction,the increasing volume of traffic made the road network under increasing pressure.As an effective solution,road widening has been paid more and more attention.The new embankment foundation treatment and the new embankment filling would undoubtedly disturb the old embankment,especially obvious in the soft soil foundation.Therefore,based on summarizing the status of soft soil foundation treatment of spliced roads at home and abroad,and the major difficulties of geotechnical engineering numerical simulation,this paper explored the optimal algorithm for comprehensive evaluation.A three-dimensional nonlinear finite element numerical model is established,in which the DJM pile was used as the transition zone,and the plastic drainage plate and DJM pile were applied comprehensively.The treatment effect and mechanical mechanism of plastic drainage plates and dry jet mixing(DJM)piles in the improvement of soft soil for widening embankment were clarified.The main contents and conclusions are as follows:(1)To compare the advantages and disadvantages of the non-linear finite element solution algorithm for a reasonable algorithm,the elastic-plastic analysis on the thick-walled cylinder with uniform internal pressure was carried out based on the finite element nonlinear analysis software AFENA(A Finite Element program for Nonlinear Analysis),and its non-linear solution algorithms and corresponding modular macro-order were described.(2)Comparing the analytical solution,the calculation accuracy of each algorithm was compared.Using Analytic Hierarchy Process(AHP),the comprehensive evaluation was carried out from three aspects: relative error,computer time and storage bytes.It was concluded that the optimal algorithm of elastic-plastic material is the step-by-step incremental method and the step-by-step increment should be controlled below 30% of the load.(3)With the optimization algorithm of nonlinear finite element solution,the comprehensive treatment of plastic drainage plates and DJM piles were used to widen the different transition zone widths of the soft soil foundation of the roadbed.The vertical displacement of the old embankment surface,the horizontal displacement of the foundation at the joint of the old and the new embankment,the distribution of the excess pore water pressure of the foundation during the construction of the new embankment,and the settlement change of the embankment surface after the new embankment completed were analyzed.The suitable range of transition zone for the DJM pile was discussed when the plastic drain plates and DJM piles were used comprehensively.(4)Finally,according to the results of calculation and investigation,the design and construction points of the DJM pile and plastic drainage board were summarized.