Study On Roadbed Splicing And Application Technology Of The Extension Project Of Tang Jin Expressway

With the development of national economy,some expressways built in the early stage of our country can not meet the demand of traffic growth,and it seriously restricts the development of economy.To expand the existing highway has become an important direction in road construction industry.Comparing with the newly built highway,the widening of the old road easily leads to generate a large differential settlement between the old and new embankment.Especially under the condition of soft soil foundation,the differential settlement between the new and old roadbed will be more than the differential settlement of general geological condition,and the diseases of expressway more likely to occur.In order to prevent the pavement longitudinal cracking disease caused by the uneven settlement of the extension project of Tang Jin expressway,based on the existing research results and engineering experience,this paper is about how to reduce the uneven settlement between the old and new roadbed.The main contents of this paper are summarized as follows:Firstly,by the method of orthogonal experiment design,the five factors such as the height of embankment,the amount of cutting old road,the height of step,the slope of step and the depth of soft soil foundation,which influence the uneven settlement between the old and new roadbed are analyzed.The research shows that the biggest factor is the slope of step,and the second is the amount of cutting old road,and follow is the depth of the foundation and the height of step.These two factors are close to the influence of the uneven settlement.The height of embankment is so minimal impact on the factor of differential settlement.Therefore,it should pay special attention to the excavation process of old roadbed,and the excavation step of the old roadbed will directly determine the success of roadbed widening project.O n the basis of this research,the parameters of excavation step of the old roadbed on the typical road section of the extension project of the Tang Jin expressway are put forward.Secondly,based on the research above,it excavates the old roadbed’s step of the typical road section of the extension project of Tang Jin expressway,and considering the weight of new subgrade and the traffic load,the relationship between the uneven settlement and the stress of pavement is analyzed without considering the fatigue characteristics of asphalt.Then,based on this relationship established,the standard of the differential settlement of the road is obtained by taking into account the fatigue characteristics of asphalt materials and it gets the control standard of uneven settlement,by which the pavement longitudinal cracking will not happen.And the control standard of uneven settlement of the extension project of Tang Jin expressway is 2‰ change of transverse slope of subgrade,besides,the allowable settlement value of aspha lt concrete surface layer should also be satisfied.Finally,according to the control standard of differential settlement of the extension project of Tang Jin expressway,this paper analyzes the reinforcement methods of the soft soil foundation of the exte nsion project of Tang Jin expressway.Through the comparison of settlement at the center of the roadbed、settlement on the road shoulder and differential settlement,it is considered that the reinforcement method of soft soil foundation which suitably applies to the extension project of Tang Jin expressway is the reinforcement method with PTC pile or the reinforcement method with foamed light soil.