Study On Cavities Expansion In Soils With Softening And Dilation And Analysis Of Pile Driving Effects

Cavities expansion in soils with softening and dilation and pile driving effects ware studied.By using variable transform, general solutions to cavities expansion in elastoplastic material ware obtained in case of small deformation, the solutions to cavities expansion in elastic-perfectly plastic materials and in elastic-brittle-plastic ones ware deduced.On the base of past researches, soil was assumed to be a homogeneous, isotropic and elastoplastic-brittleplastic material, stress dropping model was used to describe strain softening, a dilation angle was used to consider dilation. By using twin-shear united strength theory and non-associated flow rule, united solutions to spherical and cylindrical cavities expansion in the soils with softening, dilation and large deformation ware obtained, volume changes of the soil after expansion ware analyzed, the stresses and displacements in case of unloading after expansion ware obtained too. On these bases, some factors influencing solution results ware analyzed, and limit expansion pressures from computation ware compared with ones from survey.By making use of the characteristic of cavities expansion with zero initial radius that under limit expansion pressure, displacement field in plastic zone is self-similarity, rigorous similarity solution to limit expansion pressure was obtained.On the study of displacement after pile driving, a model of spherical cavity expansion at the pile top wile pile driving ware introduced, by making use of the solution to spherical cavity expansion and a source-source and a source-sink imaging technique, a half-numerical solution to displacement field in the soil surrounding pile ware obtained.On the premise that the problem about the excess pore pressure dissipation ware reduced to be a plane strain problem, in which the soil ware regarded as a viscoelastic material, and partially permeable characteristic of the pile was considered, a formulas of the pore pressure was obtained. Moreover, some factors influencing the porepressure penetration ware analyzed.By regarding the problem on stresses relaxation in the soil after pile driving as a plane strain problem, and assuming that the soil was a viscoelastic-viscoplastic material, formulae of the stresses and radius of the viscoplastic zone ware deduced, and by computation with program compiled by author, numerical results ware presented, moreover, several relative factors ware discussed.Famous software ABAQUS was used to analyze the stress and displacement fields due to pile driving considering softening, dilation and large strain, moreover, some factors ware discussed, and several conclusions ware presented.