Study of bearing capacity of lime-cement columns with pulverized fuel ash for soil stabilization using laboratory model

Abstract

Soft soils are generally labelled as 'problematic' because they have poor resistance to deformation, low permeability and limited bearing capacity. Thus, improvement of the weak properties of soft soils can be achieved by adopting one of the measures of soil stabilisation which are using lime, cement, sand and pulverized fuel ash (PFA) columns. Lime and cement are added as secondary constituents to further enhance self-hardening of the blended mix. The objectives of this study are to measure the bearing capacity and shear strength of stabilized sand-PFA columns when governed under drained and undrained shear strength between the columns for short-term stability, and to study the failure modes of stabilized columns on location of the failure plane when subjected to ultimate bearing capacity. The focal point of this research is to develop a new formula in calculating the bearing capacity of lime, cement and sand-PFA column that will be most beneficial for coastal zones namely the soft strata of the soil. Unconfined compression test reveals that after 28 days of curing, a 40% sand-PFA and 15% lime gives a high compressive strength two to three times greater than that of natural clay. However, when lime is replaced by cement, the initial rate of strength developed increases significantly. Excessive PFA contents (greater than 50%) however can cause tensile splitting of unconfined specimens. The compressibility of sand-PFA-lime/cement treated soil is considerably less than that of the natural clay (Terashi, 1979). As the PFA contents exceed 10% for a constant lime/cement content of 15%, the reduction of compressibility is also associated with a correspondent increase in the coefficient of consolidation. Therefore, the findings of this study present a rational basis for the development of appropriate constituent models for chemically modified soils. © 2011 ejge.