Microstructure analysis of electrokinetically stabilized peat

In this research, four new chemical grout reagents were used, namely, sodium silicate, calcium chloride, calcium oxide, and aluminium hydroxide. The injection of the chemicals through the soil by using an electrokinetic method was successfully performed. Increase in the shear strength of stabilized soil was higher in the locations near the cathode and the calcium oxide showed the highest increment. The soil microstructure is comprehensively changed due to the change in the pH of the soil, and fluid flow during the electrokinetic application depends upon time and location of samples taken along the cell. The EDX output of natural peat showed the presence of oxygen (46.2%), carbon (29.3%), silica (5.1%), alumina (2.5%), and calcium (3.0%). However, after electrokinetic injection of the sodium silicate, calcium oxide, calcium chloride, and aluminium hydroxide, the concentration of these elements in the soil samples taken adjacent to the anode changed, with the carbon changing to 24.9%, 16.5%, 31.4%, 34%; the oxygen to 47.6%, 41.9%, 53%, 46%; the silica to 12.3%, 4.1%, 4.2%, 4.7%; the alumina to 2.5%, 1.2%, 2.2%, 6.2%; and the calcium to 1.8%, 18.6%, 6.1%, 2.6%, respectively. © 2013 Elsevier Ltd. All rights reserved

Peaty Soil Improvement by Using Cationic Reagent Grout and Electrokintic Method

Peat is known as soft soil with low shear strength and high compressibility. Electrokinetic injection technique is being used by applying a direct electrical potential across the soil specimens to improve physicochemical characteristics of the peat. Such applications cause electrochemical effects on the soil, leading to changes in the soil's chemical, physical, and mechanical properties. This paper presents the results of the undrained shear strength, pH, water content across the electrokinetic box after injecting the cationic grouts. Four cationic grouts namely; calcium chloride, calcium oxide, Aluminum hydroxide, and sodium silicates were selected as grout. The microstructures of the stabilized peats were investigated by scanning electron microscopy and energy dispersive X-ray spectrometer analysis. The result showed that the cationic stabilizer injected by the electrokinetic technique could significantly increase the peat soil's shear strength. Furthermore, the result showed that the effect of calcium oxide was the highest on the shear strength of peat due to its physico-chemical properties. The shear strength, pH and moisture content of peats across the electrokinetic box also altered depending on the used electrolytes and time. © 2014 Springer International Publishing Switzerland

Shear strength parameters of unsaturated residual soils

The shear strength envelope for unsaturated soil requires that three shear strength parameters be defined namely, c', ø' and øb. These parameters can be measured in the laboratory. The c' and ø' parameters can be measured using standard laboratory equipment on saturated soil specimen. However conventional triaxial and direct shear equipment require modifications prior to their use, i.e. for suction induced tests on unsaturated soils to measure the øb (i.e. the change in shear strength with respect to suction). This paper describes the modification made to the standard laboratory triaxial and shear box and outline the test performed for measuring the shear strength parameters of unsaturated residual soils. The value cohesion, c' is found to increase with increase in the matric suction. For a given level of matric suction, the cohesion appear to increase with increase in the soil weathering grade, i.e as the soils/rocks becomes more weathered. The angle of friction, ø' decreases with increase in the soils weathering grade, but the angle of friction or change in shear strength with change in suction, øb , increases when the soil becomes more weathered. The values of øb are generally lower than ø