Numerical Analysis The Subgrade Deformation Of Subgrade Widening

With the sustained and rapid development of China national economy, road traffic is constantly increasing. The original road construction can't meet the increasing traffic demands, and need to be broadened urgently. Due to the different characteristic and different consolidation extent and compression between new roads and old ones, differential settlement appears between them,which lead to vertical and horizontal cracks ,damage and elevation at new-old fringe zone and road surface. Therefore, the analysis of new and old roadbed deformation on the widening project is critical. In this paper, the finite difference software FLAC is used to analyse interaction between new and old roadbed. Geogrid deal is applied to the new-old fringe zone. For the cases of geogrid deal to new-old roadbed fringe zone,pipes reinforcement to soft soil and pile-supported roadbed, the new and old roadbed settlement, lateral displacement and differential settlement were systematic analysed. Following is the research results:1.The software FLAC was used to establish the typical soft soil roadbed widening project numerical model. The interaction between new and old roadbeds was analysed,and the impact of the width of roadbed, filling height, filling weight,filling modulus on the roadbed deformation was studied.The result showed that the new roadbed increased the settlement of old roadbed.The greater the width of roadbed, filling height, the larger the differential settlement. The greater filling modulus and the smaller filling weight, the differential settlement was smaller. According to the differential settlement of widen roadbed and treatment measures of combination, soft soil treatment program was chosen in the widening project.2.In order to analyze the measures of combination of new and old roadbed ,the Geogrid of software is used to simulation and analysis the subsidence and deformation of inhibition provided by the Geogrid ,which laid on combination of new and old roadbed. Study rule of roadbed settlementthe influenced by the different paving method and the spacing of Geogrid. The caculation showed that the desired results was gotten by using full roadbed laying method or one end fixed method.The differential settlement decreased with layer distance decreased.Perfect economic consolidation effect could be gotten when the layer distance reached the critical value-one meter.The greater the geogrid modulus,the smaller the differential settlement. According to the calculation results,the layer floors of geogrid and laying method was determined at the new-old fringe zone.3.Study the settlement and pile stress characteristics of pile strengthening soft subgrade and systematic analysis the influence of pile length,pile spacing and pile modulus on the settlement and deformation on widen subgrade ,by slecting the pile element and changing pile modulus.The caculation results show that: the longer the pile is,the less the differential settlement and lateral deformation happens , especially when the pile penetrates the soft soil layer;with the pile spacing decreases,the subgrade deformation also decreases ;the increasing of modulus has good effect on subgrade strengthening.Comparing the three factors,pile length has the most important influence on subgrade deformation.4.Analysis the law of settlement and deformation of pile-supported reinforced embankment and research the effect of pile top cushion modulus and cancellus height on subgrade deformation by chaging the modulus and height of pile top geotechnical cancellus. The caculation results show that: with the increase of cancellus ,the subgrade settlement decrease gradually when the modulus is given;with the increase of mudulus,the maximum settlement and differential settlement obviously reduces.