The Uneven Settlement Of Highway Subgrade Widen By Numerical Analysis

With national economy high speed development continuously, the highwayconstruction has entered the rapid development of freeway, the mileage increasing, thequality is becoming more and more good;But at the end of last century in our countryto build the highway to the traffic flow is saturated, mostly four-lane roads, roadservice is also a big than before, to broaden its reform is imperative.But, after inwidening because of the new and old roadbed construction time differences and thedeviation of the roadbed itself characteristic, in the foundation degree of compressionand consolidation degree difference, it will appear the new and old roadbed unevensettlement, so there is no reasonable processing methods, the new and old roadbedthru out the elevation difference, breakage, cracks will occur, so the new and oldroadbed broaden the uneven settlement will happen after the problem has veryimportant practical significance.Heilongjiang province has the application of highway subgrade wideningreconstruction practice. Through the study of case expressway wideningreconstruction, using finite element software, the standard for the new old roadbedwidening uneven precipitation occurred in numerical analysis, found the rule, theimprovement measures are proposed for the problem.First of all, introduces the basic theory involved in the surface settlementdeformation.Analyzing foundation stress, stress including gravity stress and effectivestress, and then based on the principle of superposition, to produce at any location inthe foundation of additional stress is calculated, the additional load new embankmentwas deduced.Contrast analysis of the different soil constitutive model, the soilelastic-plastic theory are introduced, the finite element numerical calculation ofmiddle-earth constitutive model using the Drucker Prager model, to introduce somesimple finite element method and introduces the large finite element softwareABAQUS, on this basis, the finite element models of roadbed widening.Conclusion:the result of the numerical calculated, because the old between the new and oldroadbed subgrade by the new embankment to the additional stress caused by theuneven subsidence deformation, the new and old roadbed stress concentration placeappear;On both sides of subgrade top surface subsidence from the center to thesubgrade cross-section along the vertical distribution is scoop type.The results showthat if the increase of the width broaden, caused by the new embankment will give the increase of the vertical settlement and horizontal displacement is obvious;Present thelinear increase of the old top of roadbed and broaden the width of the horizontaldisplacement, the characteristics of the top horizontal displacement of the newroadbed is first increases then decreases.In addition, the vertical additional settlementcurve located at the top of the subgrade, a spoon shaped distribution, when the largerthe width of the spoon type, the more significant, in the new subgrade and oldsubgrade similar shoulder inside the maximum settlement, rather than at the newroadbed shoulder.In addition, increase broaden the width of the cross between newand old roadbed slope on the change of overall is increased, the increasing trend, isgradually become smaller.The same broaden the width of the situation and broadenthe width change is different, increasing subgrade height, new the maximumhorizontal displacement of the surface change is in the direction of the far away fromthe old subgrade;Its vertical settlement curve will show that the uneven settlement ofthe exercise, will slowly become inclined straight, at the same time there will be asettlement points to new and old roadbed combined position now.Simulation of digging up the steps of the new and old roadbed integration of datashow that dug a steps of uneven settlement does not have a large impact.Finally, theanalysis of the results of numerical simulation, said the new roadbed width or theheight of the roadbed filling, in the bottom of the new roadbed laying geogrid touneven settlement between the old and new roadbed effect reduced to some extent,the width of the cut new roadbed, the effect of geogrid will become moreobvious;Roadbed fill height is lower, the effect of geogrid and more obvious, lightweight embankment to broaden the compared with the ordinary embankment, theformer can effectively reduce weight, reduce uneven settlement effectively.Analysisresults show that the elastic modulus of embankment of uneven precipitation noembankment density change is big, the influence of uneven settlement problem can besolved through the use of small bulk density of lightweight embankment.Through thestudy of this article, and the result has reference significance for highway roadbedbroaden the construction.