| Hydraulically filled clay is a special type of recent man-made soft soils and after improvement,the residual settlement from sequent secondary consolidation still has the significant influence upon normal usage of structures and maintenance in use. Considering relatively few studies and much more laboratory stimulation tests,the existing researches do not reflect the truth of the secondary consolidation of improved hydraulically filled clay.Based on an engineering in Dongjiang port district of Tianjin Port,the consolidation and secondary consolidation of improved hydraulically filled clay as long with influencing factors have been profoundly studied by one dimensional consolidation tests with automatically datum-collecting facilities in this thesis. In datum processing for it,so numerous data have been adopted to compute the arithmetic mean value by mathematic statistics that the research result even more approaches to the truth since the error between this average value and the true value has been largely eliminated. Therefore, this thesis provides the basis for reducing the residual settlement of improved hydraulically filled clay and taking precaution and can be utilized as a reference to study the similar problems.The comparison between the hydraulically filled clay improved by vacuum preloading and the originally underlay marine clay with the same composite in physical properties,shear strength,consolidation,genesis and engineering application has been systematically first discussed in this paper. And then the general characteristics of secondary consolidation coefficient variation has been indicated with loading. The consolidation coefficient of improved hydraulically filled clay under the first load is found to be even larger in one-dimensional consolidation test and becomes gradually smaller with loading down to a constant value for the saturated undisturbed soft clay with the moisture content exceeding 40%,which is especially analysized in the paper.The influence of loading rate on the consolidation coefficient and the secondary consolidation coefficient of improved reclaimed clay has also been studied by the load rates of 0.5,1.0 and 3.0 in tests. To enhance the treatment effect and decrease the residual settlement, small loading increase load rate and multi-step loading are hereinafter recommended to adopt under the certain ultimate gross load in the soft clay treatment. When too small loading rate is utilized in test, the curves of consolidation coefficient versus load and secondary consolidation coefficient versus load are found to be fluctuated, and shown the settlement rate of consolidation and secondary consolidation varies unregularly with the loading, which is elaborated.The effect of drainage path on the primary consolidation and the secondary consolidation has been investigated by the one-dimensional consolidation test with the specimens of variable height and the result is discussed with theoretical formular.The influence of surcharge preloading, repeated surcharge preloading and relief rebounding upon the primary consolidation and the secondary consolidation has been finally studied by two surcharge preloading tests and relief rounding test and a conclusion is drawn that surcharge preloading and repeated surcharge preloading can effectively reduce the residual settlement from the secondary consolidation. |
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