Experimental Study On Electro-osmotic Consolidation Of Soft Clay

Soft clay exists extensively in the southeast of China and Zhujiang delta region. Foundation improvement must be implemented before construction because of its bad engineering properties including high water content, high compressibility and low un-drained shear strength. Usual foundation treating methods such as preloading method, vacuum preloading method could not achieve a satisfactory result because they relied on hydraulic permeability of soil. More attention was paid to electro-osmosis in recent years just as the method was irrelevant to hydraulic permeability. There were several problems which need to be solved as soon as possible while many investigators at home and abroad have gained in the electro-osmotic reinforcement, including mechanism, calculation of initial resistance. So several series of tests were conducted in the electro-osmotic consolidation apparatus which was developed newly by authors.The major studies and achievements in this thesis are as following:1. The application history of electro-osmosis in the civil engineering was summarized; the microcosmic process and basic mechanism were concluded at the basis of lots of phenomena showed in the literatures published; the advantages and disadvantages of electro-osmosis were given after comparing with other methods, so as its applied range; one-dimensional consolidation theory and its analytic solution in the three different boundary conditions were given, the characteristic of excess pore water and consolidation degree varied with treating time were acquired.2. Three-phase parallel resistivity model for clay during electro-osmosis is developed and the calculating formulations of soil resistance at the beginning of electro-osmosis for different forms of electrodes are given; tests were carried out to judge validity of resistance formulations, and the result shows formulation will be credible while water content is above 25% and degree of saturation is above 50%; resistance formulations can be helpful to preliminary design of electro-osmotic application.3. Four electro-osmotic tests using Hangzhou clay under different initial and current condition were conducted; effluent volume, current intensity, voltage distribution and settlement during electro-osmosis were monitored, un-drained shear strength and water content before and after electro-osmosis test were also measured; the consolidation properties and the effect of electro-osmosis to physical and mechanical properties of soil were given after analyzing parameters mentioned above.