Electrokinetics-generated pore fluid and ionic transport in an offshore calcareous soil

In this study, the electrokinetics-generated pore fluid transport in an offshore calcareous soil is investigated in three steps. The pore fluid of the soil specimen tested has a salinity equivalent to that of seawater (artificial or A-seawater). The electroosmotic flow rates are measured for the A-seawater and two stabilizing permeating solutions, i.e., 15% CaCl2 and 10% Al-2(SO4)(3).18H(2)O solutions. The results show that electroosmosis generated significant flow in the soil and can effectively transport the two permeating solutions through soil pores filled with A-seawater. The maximum flow rate is observed in the test conducted with 15% CaCl2 solution, followed by those of A-seawater and 10% Al-2(SO4)(3).18H(2)O solutions, respectively. The results also show the significant role of electromigration in transporting the cations in the permeating solutions from the anode to the cathode. In particular, it is found that the electrokinetics-generated ionic transport for calcium (Ca2+) is 6.3 times faster than that for aluminum (Al3+). The surface charge properties of the calcareous soil are studied by measuring the zeta potentials of the soil solids suspended in electrolyte solutions of various types, concentrations, and pH values. The relationship between the experimental and theoretical coefficients of electroosmotic permeability, k(e), is examined based on the results from the electrokinetic experiments and the Helmholtz-Smoluchowski model. It is concluded that the effectiveness of electroosmosis in transporting water can be predicted qualitatively or semiquantitatively from the zeta potential of the soil solids suspension. The influence of pore fluid pH on the zeta potential of the soil is also investigated. The study provides important information for the use of electrokinetics to facilitate in situ artificial cementation of calcareous soils for offshore foundation applications.