Study On Slope Deformation And Interaction Between Reinforced Piles And Soils

Laboratory tests, field tests, centrifuge model tests and 3D finite element methodare carried out to study the shear strength parameters of soil in stability analysis, slopedeformation and the interaction between the reinforced piles and the soils. The mainworks and conclusions are as follows:(1) The conventional definition (criterion method) of shear strength parametersof soil from triaxial CU test are not consistent with the principle of effective stress andcase history. It is more reasonable to define the shear strength parameter of soils intriaxial CU test with consolidation pressure, that is, tanφ_cu=τ_f/σ_c(new method).From different stress path triaxial CU tests, we find that the shear strength parametersobtained from the criterion method are obviously different, but they are almost samefrom the new method.(2) The procedure of selecting material, model construction, test technology inthe centrifugal model tests for the levee project are introduced. Deformation andfailure mechanism of levee project are studied by means of centrifuge model testsusing aboved test method.(3) After analysizing the results of SSRFEM and centrifugal model test, someconclusions are drawn that, the depth of slip surface implies that the Bishop'ssimplied method cannot indicate the true failure mechanism for the slopes reinforcedwith piles. The rate of safety factors decreases with the pile spacing decreasing, andthe salty factor of the slopes is the largest when the reinforced piles are installed in themiddle of the slopes, regardless of pile head confining conditions, and the deflection,maximum bending moment and shear force in the reinforced piles in the criticalcollapse are the biggest meantime. The fixed and hinged head condition of the pilesresults in smaller bending moment in the piles than that in unrotated and free headcondition, therefore the restrained pile head condition is recommended in the design.(4) At the same material quantity of reinforced piles, the smaller the diameter andspacing are, the bigger the safety factors are. When the D1/d (D1 is the center-to-center spacing between the piles, and d is the diameter of the piles) is thesame, the bigger reinforced piles diameter is, the bigger the safety factor is.When theD1/d and d are the same, the safety factors of global slope increase with the pilemodulus. With the bending siffness (Eplp) of piles are same, it is more effective toincrease the pile diameter in comparison with increasing piles modulus.(5) Bigger safety factors can be obtained with two rows of piles than one row atthe corresponding position, and the deflection, maximum bending moment and shearforce in the piles in two rows are bigger than those in one row at the same position. Itis more effective to set two rows of piles in middle of the slope than in the toe andshoulder of the slope.