Test Study on Strength and Permeability Properties of Lime-Fly Ash Loess under Freeze-Thaw Cycles

Abstract

Abstract:In order to study the application of lime-fly ash loess in permafrost subgrade engineering, uniaxial compressive test, fast direct shearing test and permeability tests were carried out on lime-fly ash loess under different curing ages and freeze-thaw cycles. Uniaxial compressive strength of lime-fly ash loess increases slowly with the curing ages, and can reach 3.5 Mpa after the curing ages of 90 days (This strength is called 90d strength). 14d strength of lime-fly ash loess has already reached 50% of 90d strength; later strength including 28d strength and 90d strength is basically stable under different freeze-thaw cycles, so lime-fly ash loess has good water stability and freeze-thaw stability. Fast direct shear strength decreases with the number of freeze-thaw cycles without consideration of moisture content; the coefficient of permeability increases with the number of freeze-thaw cycles．All test data show that lime-fly ash loess with good behaviors can be applied in permafrost subgrade engineering.

Experimental and Mathematical Investigations on Unconfined Compressive Behaviour of Costal Soft Soil under Complicated Freezing Processes

“…Effect of suction on unconfined compressive strength in partly saturated soils was discussed 2 and the unconfined compressive strength of compacted granular soils by using inference systems was discussed 3,4 . In some case, soil foundation or slope may experience freezing-thawing circle (FTC) process due to nature season change, day and night temperature difference, or artificial freezing engineering, which would make big difference to unconfined compressive strength of soil 5,6 .…”