The Research On Road Widening Project Of Low-grade Highway Under The Condition Of Soft Soil Foundation

In recent ten years,with the sustained growth of the total highway amount,many of the technical grade of the road and the road level are further improved.Therefore,there are more and more highway upgrade project.Highway upgrade include new project of highway and the highway econstruction and extension project。The highway econstruction and extension project including embankement widened engineering,It is the use of the existed old road,and to make widening and repaving design,it can improve the road grades or improve the road service functions,so as to improve the existing road network structure,make it has a higher technical and economical value,while the use of old road can be less use of land and benefit for environment protection.In our country,many low-grade highway are builded in soft soil foundation, due to the inherent complexity engineering properties of soft soil foundation,embankement widening project based on soft ground is more complicated.The Paper is related to the low grade Lakes Highway upgrade project,further studying on the embankement deformation characteristics,treatment measures and supervision on soft base for low-grade highway embankement widening project based on soft ground foundation.In this paper,through the research and study of the relevant literature and theory about embankement widening and soft ground foundation both at home and abroad, summed up the key technical problems of subgrade widening under the conditions of on soft ground foundation. namely,the prombles of weak sub-grade treatment and Junction between new and old embankments. To determine the main contents and technical line of this paper,the specific implementation is as follows.Through the laboratory test with soft soil of Tie-Tao highway of YueYang,the paper research its basic physical parameters,the performance of compression consolidation,permeability and shear behavior,and sum up the conclusion that soft soil has engineering properties of "three high-low",that are,high water content,high void ratio,high compressibility,low permeability,low consolidation coefficient and low intensity, these characteristics determined it can not be directly laying the subgrade as a natural embankement,and it necessary to use the appropriate method to reinforce. Based on the the choice of constitutive model on Embankment and soft ground foundation and the introduction of large strain consolidation theory, it uses large-scale finite element analysis software FLAC Analysis the characters about embankment widening on the foundation under the different conditions, finds new and old embankment to identify the impact of uneven settlement of the factors and differential settlement between the changes in the law, provides a theoretical reference to reduce the settlement of new and old embankement.Combined with entity project,it simulates embankment widening project on soft ground foundation that is not treated in section K52+100,studys more comprehensively the properties of the embankment widening , Masters Changes and Distribution horizontal displacement and Settlement on the process of Embankment widening on Soft Foundation, identifys the deformation behavior of soft foundation and widening damage traits. Then, based on the current commonly used treatment of soft foundation measures and to reduce the differential settlement of new and old embankement measures, it proposes treatment of the cross-section of the program. Then it simulates embankment widening project on soft ground foundation that is treated in section K52+100, the results compared with the measured data to verify the correctness of choice of model parameters. Finally, it uses software simulation and Gray Theory predicts embankment settlement to evaluate whether the treatment effect of the settlement after the standards allow. Based on the curve of embankment Settlement in accordance with the time, it determines the earliest time the road paved. Finally, it advances the structural design of the road widening program.Combined with entity to carry out the settlement project and the lateral displacement of the monitoring, through the monitoring results it indicates that treatment programs are effective, dentifys distribution and changes about the soil settlement and lateral displacement.