Quantitative Radial Attenuation Of Vacuum Pressure And Large-Strain Vacuum Consolidation Model For Dredged Clays

It is found that in practical applications dredged clays are treated effectively within the "soil pile" with the prefabricated vertical drains(PVDs)as the central axis under vacuum preloading,and the clayey soils far away from PVDs still have poor engineering properties.The radial propagation law of vacuum pressure is the key scientific issue to reveal the poor vacuum consolidation effect.Based on model tests,theoretical and numerical analysis,the laws of vacuum pressure propagation and consolidation deformation of the dredged clays with different initial states during vacuum preloading are studied,the formation mechanism of "soil pile" is explored.The main works are as follows:(1)The vacuum pressure propagation attenuation model tests for the dredged clays with different liquid limit and initial water content were carried out.The variation laws of vacuum pressure radial attenuation coefficient,growth coefficient and time-delay factor were elaborated,and the mathematical description of the vacuum pressure radial time-varying distribution in the dredged clays was constructed;(2)The tests of water content and shear strength after vacuum consolidation for the dredged clays with different liquid limit and initial water content were conducted.The vertical and radial distribution of water content and shear strength was discussed.The relationship between the vacuum pressure radial propagation attenuation and the variations of water content and shear strength of the dredged clays was established,and the radial effective range under vacuum consolidation was evaluated quantitatively;(3)The duration monitoring of surface settlement and excess pore-water pressure in the vacuum consolidation model tests for the dredged clays with different liquid limit and initial water content was carried out.The characteristics of the non-uniform deformation for the dredged clays with higher water content under vacuum consolidation were analyzed,and the influence of vacuum pressure propagation attenuation and time-delay on the radial surface settlement and excess pore-water pressure dissipation was discussed;(4)A large-strain consolidation model considering vacuum pressure radial attenuation and time-delay was proposed,the influence laws of vacuum pressure propagation attenuation and time-delay on the consolidation deformation were analyzed,the applicability of the proposed model to predict the consolidation deformation of dredged clays with different initial states was discussed,and the influence of lateral deformation on the consolidation deformation was further pointed out;(5)Based on the plane strain equivalent method,the numerical analysis of twodimensional large-strain vacuum consolidation for the dredged clays with different initial states under the vacuum pressure radial attenuation and lateral deformation was carried out,the influence of lateral deformation on the vertical non-uniform deformation was explored,the formation mechanism of "soil pile" was improved.