Studies On The Structural Performance Of Embankment Slopes Reinforced With Geogrids

As we known, soil can bear fairly high pressure but its tension ability and shear strength are very low. It causes that backfilled slopes are ease to deform over capacity and fail. Lay geogrids horizontally in backfilled soil mass is a new geo-technology. In decades, it developed very fast all over the world. Just as reinforced concrete, geogrids can confine the lateral deformation and enhance the integrate of soil mass. This geo-technology will be used widely in geotechnical engineering in the near future. Now, because people have rather poor understanding to the interaction between geogrids and soil mass, the application of geogrids is limited greatly.Firstly, the engineering properties and reinforcement mechanism of geogrids are introduced in the dissertation, and it is compared with another geosynthetics reinforcement --geotextile on the base of consulting the national and international materials.Secondly, the structural performance of backfilled embankment slopes reinforced by geogrids are studied, namely, reinforcement coefficients such as the spacing, number of geogrid layers, tension ability of geogrid and slope factors such as slope angle, cohesion, angle of internal friction, unit weight and so on how to affect the stability of slopes. Base on the traditional Bishop arc method, reinforcement is considered and programming with Fortran. By the program and associated with single index multiple factors orthogonality analysis table, the sensibility of factors of uniform slopes reinforced by geogrids are compared and lay emphasis on the factors of reinforcement; Next, by calculations, a conclusion is drawn that the more reasonable reinforcement spacing should be "sparse in top but dense in bottom of slopes ", not the equal spacing or local equal spacing in the code. Then, Monte-Carlo random model method is adopt to analyze the progressive failure character of the uniform slopes reinforced by geogrids and some useful conclusions about the reinforced slope structure are drawn.After theoretical analysis, small scale model tests are done. Two slope angles: 1:1 and 1:1.2; two kinds of single oriented geogrids: Tensar 40RE and 80RE and three reinforcement layers: zero, one and three layers are analyzed. Totally ten test cases' deformation of slopes, geogrids and the failure modes are measured. After the tests, FEM software, ANSYS 5.7 is adopt to calculate the embankment slopes. Base on the test results and the calculation results, the contributions of reinforcement coefficients to the stability of embankment slopes are discussed.In the end, the conclusions about the embankment slopes reinforced by geogrids in the master dissertation are summarized, the prospects of the new geo-technology is foreseen and some problems need to solve urgently are proposed.