Numerical Analysis Of Differential Settlement Of Expressway Subgrade Widening

With the sustained and rapid development of the national economy, the construction of free way is at an unprecedented pace of development forward. The freeway's mileage grows continuously and the quality of freeways improves greatly. But in the end of the last century, most of the construction of highways throughout the country is four lanes, the traffic volume has reached saturation point, the road Service levels were significantly decreased. There is an urgent need to broaden the transformation. Because after broaden their new and old roadbed of the old road construction and the new time difference, resulting in the foundation level of consolidation and compression caused difference in the extent of the new and old roadbed differential settlement. If handled improperly will lead to the vertical and horizontal cracks at the combination of the new way and the old way, damaged, elevation difference, and so on. Therefore, to expand the old path after the new roadbed on the differential settlement is of great significance.Through the investigations and studies of highway widening in domestic and international , generally believed that that the biggest technical challenge of the widened road projects is how to solve the new and old roadbed differential settlement, as well as the cracks resulting from this problem. In order to resolve the various diseases during widening the freeway, common treatment options: combining new and old subgrade surface treatment, widen the roadbed fill and compaction control, reinforced embankment, the light embankment, ground handling, as well as retaining structure Comprehensive Treatment, and other road subgrade. All of the above methods are in the works in a wide range of applications, and disposition of claims of effectiveness, the old way of dealing with the new subgrade settlement after instinct to meet the requirements.In this paper aim at the new roadbed old road widening project in the differential settlement, the use of finite element numerical analysis software to identify the settlement laws, and proposed a number of reduced differential settlement solution.First, some deformation basic theory of soil subsidence was introduced. The stress of the foundation under the embankment was Analysis, which including soil stress themselves and the effective stress, and then use the superposition principle, derived the tress calculation that new roadbed as additional load, in the foundation at any location within the additional. Secondly, different constitutive model of soil was analysis and compared, the soil on the elastic-plastic theory was introduced, and then choose Drucker-Prager as finite element numerical study of the constitutive model of soil.Secondly, this paper briefly introduced finite element method and the basic profiles of large-scale finite element software ABAQUS, then widened road with the finite element model was established. By numerical calculation: the new roadbed additional settlement caused differential settlement deformation of the new and old roadbed; stress concentration was found in the combination of the new and old roadbed; the vertical displacement on top of the embankment from the centre of the road along vertical displacement to both sides has a spoon distribution.Again, after the analysis of diseases on the highway widened, reduced the differential settlement of two measures were analyzed. Through investigation found that the new widened road manifestations of the disease are mainly four. This article analysis the reason of road damage. Broaden against diseases that can easily arise in the road widening, different broadening programmers of the numerical simulation was comparative analysis. The results of the analysis showed that: with the increase in the width widening, the new roadbed caused displacement and the level of vertical displacement have increased significantly. The horizontal displacement on the top of old roadbed as expand the width increases linearly increase, the horizontal displacement on the top of new roadbed is increased first and then decreased. In addition, the top of the subgrade settlement Additional vertical curve of a spoon, shape the widening significantly greater width, the maximum settlement is not there in the new roadbed shoulder, but in and around the old roadbed of the new roadbed shoulder inside. Also, the increase in width as broad banding, new and old roadbed between the horizontal gradient change the overall trend was an increase from the trend, the increase in volume is getting smaller and smaller. And expand the width is slightly different changes with a widening the width of the situation, with a high degree of increase roadbed, the new roadbed top of the horizontal displacement maximum points away from the old roadbed to the direction of movement. Its vertical displacement curve gradually tilted to the straight-line transition, demonstrated the dramatic differential settlement, at the same time in the integration of new and old roadbed there is a settlement break point. After the results of numerical simulation analysis, digging level has no impact on the differential settlement.Finally, from the numerical simulation results, in different heights and different embankment construction of the new roadbed width, laying at the bottom of the roadbed in the new geogrids had a certain extent reduced the old roadbed of the differential settlement. The smaller width of the new roadbed, the more obvious role that geogrid in reducing settlement. The lower height roadbed fills the more obvious role in reducing geogrid differential settlement. Compared with ordinary embankment, light embankments reduce the weight themselves, effectively reduced the differential settlement. From the analysis results, changes in density than changes in the elastic modulus have a more signify impact on the differential settlement. Under the same conditions, choosing light embankment with small density will have a more obvious effect on reducing the differential settlement.The results of this paper can give some advice to the subgrade of road widening.