Research On Behavior Of Settlement And Consolidation Of Non-typical Soft Soil

The consolidation behavior and the testing methods of soft soil have been extensively studied presently, however, the calculated settlement is different from the monitored one, for the complexity of the soft soil's characteristics and the uncertain factors during calculating settlement. The nature ground in north shore of the YANGTZE river delta, mainly consists of alternative layers of clayey, silty and fine sandy soils, whose engineering characteristic is different from that of clayey soil or sandy soil. The natural water content of the intermediate soils is almost the same to the liquid limit of the soft marine clays, but its in-situ strength and its sensitivity are much higher than the latter. So it is necessary to study and analyze the permeability and the consolidation behavior of those soft soils, and it is significant to the study of the applying soils mechanics and the construction of the highway in that area.The existing settlement computation methods are evaluated and analyzed firstly. Based on the analysis of the in-situ settlement data of Tongqi expressway, and using the statistical analysis system(SPSS), the simplified settlement prediction formulas of different ground treatment are presented. Furthermore the consolidation behavior with a system of vertical and horizontal drain is discussed using the transfer matrix method, which is proved to be a practical computation method to solve the one-dimension consolidation of the multi-layer ground.On the basis of the sedimentary properties of deposit in the YANGTZE river delta, the permeability and consolidation characteristic of the special regional soil is analyzed. And its permeability and consolidation coefficient measured in the laboratory is generally smaller. However the permeability coefficient is successfully predicted by the improved pore medium model. The predicted results show that the permeability coefficient of the soil in the YANGTZE river delta is 1 magnitude greater than that measured in the laboratory. Based on the consolidation theory, the back-calculating method to compute the consolidation coefficient from the field settlement measurement with amending the reinforced area and the underlying stratum is put forward. The back-calculated results show that the coefficient of consolidation in YANGTZE river delta is 1~2 magnitude greater than that measured in the laboratory. The method is applied to analyze the ground settlement, and the results show that there is a good consistent between the calculated settlement curve and the surveyed curves.