Research And Application On Geogrid Reducing Rut On Soft Foundation's Pavement

In recent years, geogrid has been widely used in water conservancy, railways, highways, ports and construction projects, and there are also many projects concerned with the use of geogrid to reinforce soft soil roadbed of highway. But the role geogrid plays in reducing rut on soft foundation's pavement is not very clear and methods of calculation are imperfect and cannot meet the practical engineering requirements. In order to provide theories for the design and construction of soft foundation by reasonably using geogrid, it is of great necessity, therefore, to do a further systematic study on geogrid's reinforcement of soft foundation to increase its anti-rutting ability through the analysis of soil tests and rutting test.Firstly, The results of experiments on test materials (soft soil, graded gravel and geogrid), and rutting tests between non-geogrid soft foundation and soft foundations reinforced by geogrid in different structures, materials and producing technologies, show that, deformation degree of ruts on reinforced pavement reduced by 23% compared with unreinforced ones. Comparing the effect of different geogrids, the mesh triangular geogrid of the lowest tensile strength, TX170, has the best anti-rutting effect which is because the embedded and squeezed structure formed between its structure and the graded gravel can perform the function of geogrid more effectively.Secondly, on the basis of original experimental data, the paper develops a finite element model. The finite element analysis further proves the experimental results of geogrids in reducing the effect of ruts on soft foundation, and gets various parts'stress and displacement which are unable to be measured in experiments and it is easier to make visual analysis of models'stress and deformation characteristics under load. Meanwhile, through the analysis of different factors, the paper also summarizes the impacting laws various factors on rutting, mainly proves that simple increasing the modulus of geogrid has little influence on reducing the effect of ruts on soft pavement. And everlasting emphasis on increasing quantity is not always correct. Finally, based on experiments and finite element analysis, the paper knows the origin and formation of ruts in the test by mechanism analysis, summarizes the different working mechanism the bearing capacity of reinforced soil and deformation, choose a more suitable theory for this study---- improved Terzaghi ultimate load-carrying capacity theory which can effectively prove that in dealing with the soft foundation geogrid has added a foundation bearing capacity. Via further study on the interaction between geogrid and soil, and geogrid's reinforcement mechanism, the paper researches that the effects of geogrid rely mainly on the interlocking effect, the friction effect and the wave effect between soil and geogrid, and consequently geogrid can reduce the effect of rutting on soft foundation.