LIQUEFACTION STUDIES ON SAND AND SAND-SILT MIXTURES

Abstract

One of the major cause of catastrophic damage, to the structures during the earthquakes, has been liquefaction of loose and saturated cohesionless soil deposits. Structures resting on such deposits may experience large scale tilt, movements and damages, due to the liquefaction of foundation material, resulting into loss of valuable life and property. The analysis and mechanism of liquefaction, has been well developed. But there is a need for research, on stabilizing a potentially liquefiable sand deposit. The proposed investigation aims to study the effect of fine silts in stabilizing a potentially liquefiable sand deposit. These investigations have been carried out, without imposing any surcharge load. In the proposed investigation, fine locally available SOLANI SAND and DHANAURI SILT has been used. Different silt percentages i.e. 2%, 4%, 6%, 8%• and 12% are used. The mixtures are prepared by dry mixing. After preparation the mixtures are deposited in a test tank of size 1050mmx 600mmx 600mm and subjected to sinusoidal vibration. The frequency of the vibrations has been fixed at 4cps. The accelerations used are 10%g, 20%g and 30%g for first set tests and 20%g, 30%g and 40%g for second set tests. The initial relative density of 30% has been maintained for all the tests. Three piezometers of rigid steel pipe extending into the centre of the tank, have been installed at three different depths of 80,160 and 240 mm, from base of the tank. PVC tubes and a manometer graph have been used, to study the rise and fall of dynamic pore water pressure.