Study On In-situ Measurement Of Soil Consolidation And Permeability Characteristics And Its Applications

Consolidation and permeability coefficients are key parameters in calculation and designing of foundations, CPTU and BAT-system can obtain the consolidation and permeability coefficients quickly and accurately. Additionally, land reclamed by dredger soil can solve both shortage of land and dredger soil's problems during dredging, and Vacuum consolidation is an effective method to accelerate the consolidation of dredger soil. So the study on the consolidation characteristics of dredger soil under vacuum pressure is necessary. Based on the study of predecessor, the in-situ test theories and consolidation characteristics of dredger soil under vacuum pressure were studied by theoretical analysis and model tests.Based on Vesic's cavity expansion theories and 1-D radial consolidation equation, analytical solutions of cylindrical and spherical cavity consolidation considering shear stress under arbitrary drainage boundary were gained. Analytical models for different CPTU or BAT-systems were gained, and the testing principle and procedures of IFCO BAT-system for consolidation coefficient were described. The pore pressure curves by the theoretical solutions are close to the results of in-situ tests, and the laboratory consolidation coefficients agreed .well with in-situ values. It shows that the analytical solutions and methods of coefficient's estimation are reliable.The testing principle and procedures of IFCO BAT-system for permeability were described latterly, and theories of permeability for IFCO BAT-system were generalized too. Theoretical model was described considering both flow-resistance and water column of filter and container, and analytical solution was gained under linear flow-resistance. The pressure curves by the theoretical solution agreed with the curves of field tests, and permeability coefficients by IFCO BAT-system were close to the laboratory values of undisturbed soil. The comparisons show that the theoretical model of permeability for IFCO BAT-system is rational.Finally, combined with IFCO BAT-system and TDR system, a model test was designed to study the consolidation characteristics of dredger soil under vacuum pressure. The relationships were gained among permeability, void ratio and effective stress of dredger soil under vacuum pressure. In addition, an consolidation model of dredger soil under vacuum was gained additionally, and the pore pressure and settlement calculated by theoretical model agreed well with the results of model tests, so the theoretical model is rational for dredger soil under vacuum pressure, and it also shows that vacuum pressure is an effective method to accelerate the consolidation of dredger soil.