Study Of Structured Soft Clay And Consolidation Behavior Of Sand-wall Ground

Soft clay extensively distributing near the littoral in southeast China, and the preloading method is in common use in improving the soft ground of large-scale engineering built in this area. The consolidation behavior of sand-wall ground is the key in the design of the preloading method. At the same time the structure character is the important stamp of soft clay and have strong influence on the consolidation behavior of soft ground. Therefore, the study of consolidation behavior of sand-wall ground should be based on the study of structured soft clay in order to guide the practice in reason.In this dissertation, on the basis of the test of structured soft clay, the consolidation behavior of sand-wall ground considering the structure character of soft clay is studied. And the consolidation calculation method of a new preloading method named IFCO forced consolidation method is provided. Adopting the improved general finite element analysis, the consolidation behavior of IFCO forced consolidation method is compared with typical preloading method in order to the reasonable choice of preloading method applied in the deep and thick soft clay.First, Based on the consolidation test of Wenzhou soft clay, the relation between structure character and mechanical properties of structured soft soil is examined. The different compressibility of undisturbed soil and remolded soil is compared, and the effect of the rate of loading on the compressibility is analyzed. Combined with analysis of the laboratory compression curve of soil in many regions, the existed methods of predicting the virgin compressibility curve are discussed, and a new method to predict the virgin compressibility curve is developed.Second, based on analysis of the consolidation mechanism of IFCO forced consolidation method, the consolidation calculation method of sand-wall ground including sand-wall domain and subsoil is provided. The influence of well-resistance, smear and two-way seepage on consolidation behavior of sand-wall domain was analyzed in the consolidation calculation method of sand-wall domain, and the interaction between sand-wall area and subsoil is considered in theconsolidation calculation method of subsoil. And based on the section model of the parameter of consolidation and pressure proposed after the consolidation test of structured soft clay, the consolidation calculation method of multi-layer sand-wall ground considering the structure character of soft clay changed with the depth and the staged loading is provided. The influence of the structure character of soft clay on the consolidation behavior of sand-wall ground which improved by IFCO forced consolidation method and typical preloading method is modeled well.Finally, aim at the drawback of the huge amount of element number and node number adopted in the general finite element analysis of sand-wall ground, the domain-by -domain integration technique is applied and a new element, sand-wall composite element is provided. And the consolidation behavior of IFCO forced consolidation method and typical preloading method are analyzed by this new element in order to guide the choice of preloading method which applied in the deep and thick soft clay in reason in the similar engineering later.