Experimental Study On Effect Of Variation Of Principal Stress Orientation On Intact Soft Clay

As the rapid development of economy,the construction of traffic and ocean engineering is on an unprecedented scale.So the research on the effect of vehicle and wave loads on soft clay has a very important realistic significance.The principal stress rotation is a typical stress path when vehicle and wave loads are applied on the foundation,which has quite different influence on soil's characteristics from the fixed principal stress orientation shear path in many aspects.But the study about the influence of principal stress rotation on soils need enrich greatly,especially the experimental data on intact soft clay are very few.The dissertation was focused on the experimental study on the stress-strain relationship while principal stress orientation was varied in different mode on Hangzhou typical intact soft clay.The major studies and achievements in this thesis are as following:1.Undrained shear experiments with fixed principal stress orientation had been done,and it was found that(1) The b-value had big influence on torsional strain, while had little influence on the axial strain and tangential strain,which means the b-value and the principal stress direction have little impact on them.(2) The octahedral shear strain in b=0 tests,mainly between 8%～15%,was much larger than that of in b=0.5 tests(the octahedral shear was about 3%～7%).(3) The direction of incremental stress did not match the direction of incremental strain.This phenomenon was much remarkable when the angle of principal stress increased.2.Undrained principal stress rotation experiments had been done.The conclusions were:(1) The value of axial strain,radial strain,torsional stain and tangential strain were not strongly affected after principal stress rotation.(2) After principal stress rotation,the octahedral shear strain coincided with those of fixed principal stress.(3) The magnitude of the strain developed after principal stress rotation was found to depend on the direction of rotation.(4) The directions of incremental stress and strain suddenly changed with a large magnitude as principal stress rotation began,and the deviation still existed in the end of tests.