Investigation of the Effect of Strength Anisotropy on Slope Stability of C.D.G.S

The weathering of the granite rock results in C.D.G.S (completely decomposed granite soil) in most land area. Therefore, the C.D.G.S is commonly encountered in construction field, such as riverbanks and embankments, including roads and railways, and has a stress history of compaction with their construction. In this process, the compacted soil possesses an anisotropic property. Measurement of stress-strain-strength behavior of anisotropic decomposed granite soil is very important for the analysis of deformation and stability of slopes, retaining walls and excavations. Therefore, Anisotropy of mechanical properties for C.D.G.S (compacted decomposed granite soil), a series of unsaturated and saturated-drained triaxial compression tests was performed in order to investigate the deformation and strength anisotropy of C.D.G.S (compacted decomposed granite soils). Three different orientation angles of the axial direction of samples with respect to the horizontal plane were investigated: d=0, 45 and 90 degrees. As the results showed, the compression strain of specimens subjected to an isotropic compression was influenced strongly by d. The effect of the angle d on the strength was more pronounced on unsaturated specimen as compared to saturated specimen. In addition, the time dependence was independent of the settling angle associated with the deformation behavior during the secondary compression process. The effect of settling angle on triaxial compressive strength and deformation was clearly demonstrated at low constraining stresses. Furthermore, to investigate the effect of strength anisotropy according to the height of the fill on the slope stability, slope stability analysis was performed assuming 10m, 20m, 50m, and 100m of the embankment. it became clear that by considering strength anisotropy, the stability of embankment decreased when water level within the embankment was low. In order to obtain more reliable results in the future, verification using various samples will be required.