Shao-Chi Chien

Development of a Suitable Operation Procedure for Electroosmotic Chemical Soil Improvement

AbstractTo expand the improvement region, a series of electroosmotic chemical tests was performed to study the mechanism of improvement. Results showed that injection of calcium chloride and sodium silicate solutions could improve the soil near the cathode and anode, respectively. Injection of calcium chloride solution for a rational injection time, followed by the injection of sodium silicate solution, could yield a fairly good improvement result for the entire sample. The rational time for the injection of calcium chloride solution could be obtained by selecting the time between the first and second turning points on the relational curve of total drained water volume and injection time. Moreover, appropriate concentrations of injected solutions were studied and were discussed in this paper.

Electro-Osmotic Chemical Treatment of Clay on Shear Modulus

Electro-osmosis chemical treatment (ECT) is one of the soil improvement methods used to improve the engineering properties of soft soils. The injected chemical solutions are usually a calcium chloride solution in combination with sodium silicate solution. Previous laboratory studies have shown that the injection of a calcium chloride solution followed by the injection of a sodium silicate solution during electro-osmosis is effective in strengthening soft silty clay. Very stiff cemented soil near the anode is formed after treatment due to the cementation of two chemical solutions and soil particles under applied electric field. However, most works focused on the improvement of the strength of the soil with treatment. The variation of the shear modulus on soils after electro-osmosis chemical treatment is rarely discussed. Thus, a field test of electro-osmosis chemical treatment on Taipei silty clay was carried out in this study. Six electrodes were installed with electrode spacing of 1.5 and 2.0 m. The shear wave velocity of the treated clay was measured by multi-orientation bender elements. The bender element test results show that the maximum improvement ratio of the shear modulus is about 200 % at positions near the anode and the cathode. The pH value and concentration of Ca2+ was determined by the inductively coupled plasma atomic emission spectrometer (ICP-AES) test at all positions that shear moduli was measured. Strong cementation which enhanced the shear modulus of the soft clay were also observed at the anode and cathode. Results presented in this study demonstrate that the electro-osmosis chemical treatment is effective in improving soil strength and soil stiffness.