Model Test Of Geogrid Workabilities In Soft Ground Road Widening Project

The key technical issues of the highway widening project on the soft ground, including mutual influence of old and new embankment, the differential settlement control between the old and new embankment, and combination of old and new roads and other issues. Survey research and analysis shows that, to date, the above theoretical and experimental issues little research reported, this paper for the unequal settlement and interaction issues between the old and new embankment at the highway widening project on the soft ground carry out indoor model test.Base on subgrade widening design at Guang-San highway widening project, in this paper a large-scale model test is designed to research workabilities of geogrid applied at the highway widening project on the soft ground, considering the laying geogrid with different layers and different installation location, and different differential settlement occurred between the old and new embankment, the test make a study of geogrid's stress and deformation and geogrid reinforced subgrade settlement laws at the highway widening project on the soft ground, providing the scientific basis for engineering design.Experiment showed the following results: (1) compared with the same differential settlement of foundation without geogrid, laying two or three layers of geogrid in conjunction of old and new subgrade can significantly reduce the new embankment surface subsidence. (2) it's better effect to laying geogrid in the top step than in the lower. (3) laying geogrid can significantly reduce the lateral displacement of the new embankment, strengthening the stability of the new embankment soil. (4) when the geogrid is laid in the lowest step, the maximum strain of geogrid occurred at the location where there is horizontal plane of step, the farther away from the old subgrade smaller strain and the maximum strain of geogrid with the increase of the foundation differential settlement.The results show that: old and new foundation laying geogrid can effectively enhance the stability of new and old roadbed, reducing the differential settlement of subgrade surface, which illustrates the combination of old and new foundation laying geogrid is rationality and necessity.