Research On Consolidation Properties Dredger Fill Under Very Low Pressure

Reclaimed soil foundation has lots of disadvantage engineering characteristics,such as high moisture content, large compression, low strength, and poor permeability,so it needs to be improved when it is used in the practical engineering. However, sofar the consolidation deformation mechanism of dredger fill is ambiguity, and thetheory of it is behind the practice. In order to extent the understanding of dredger fill,it is necessary to study the consolidation properties of dredger fill under the very lowpressure. On the base of permeability test, consolidation test, vacuum preloadingmodel test and the simulation analysis, the major results and conclusions acquired areas following:(1)Permeability test shows that there is a linear relationship between void ratio eand permeability coefficient k in the e-logk coordinate system when the moisturecontent is between the limit liquid46%and90%, once the moisture content is out ofthe range, the linear relationship assumption is not tenable any more.(2)Consolidation test results show that there exists a critical state point (σ′*,e*)during the process that dredger fill consolidates from ultra-soft soil stage to thecommon soft soil stage in the e-σ′coordinate system. Before the critical state point,the void ratio e of dredger fill with different initial moisture content changes alongdifferent curves, while after the critical state point it changes along the compressionline.(3)A formula of void ratio e is given for the dredger fill under very low pressurewith different moisture content.(4)By the simulation of vacuum preloading model test, simulated pore waterpressure are calculated under the two conditions of consolidation coefficient beingconstant and being a function of effective stress. Comparative analysis is madebetween the simulated pore water pressure and the measured pore water pressure. Theresult shows that the simulated pore water pressure under the second condition ismuch closer to the measurement, also it shows that there is obvious difference forpore water pressure varies with depth under the two conditions.(5)Under the condition of consolidation coefficient being a function of effectivestress, void ratio curves, permeability coefficient curves, compression coefficientcurves and consolidation coefficient curves are acquired and analyzed. In the early stage of consolidation, it can be found that these curves change heavily, while in thelate stage of consolidation, these curves seem no changes, and these parameters can beregarded as constants.(6)In the early stage of dredger fill consolidation, interaction of permeabilitycoefficient, compression coefficient, effective stress and void ratio on theconsolidation coefficient should be taken into consideration so that the real process ofconsolidation can be reflected.(7)Under very low pressure, method of consolidation test to determineconsolidation coefficient no longer applies.