Static response of fly ash columnar improved ground

This study presents the results of a series of monotonic undrained triaxial compression tests on clay specimens improved by columnar reinforcement. Th e process of loading and stress redistribution of a fly ash - clay specimen (FCS), in comparison with a sand-clay specimen (SCS), is examined in terms of stress-strain characteristics, generation of excess pore-water pressure , effective and total earth pressures, development of stress concentration, and the normalized undrained shear strength of the improved soil. It was f ound, predictably, that the deviator stress of the composite specimens was influenced by the consolidation stress, replacement area ratio, and propert ies of the column material. The stress concentration at the top of the comp osite ground which depends on the loading stage reaches a peak after the co nsolidation state and is reduced due to stress redistribution between the c olumn and the soft ground. In terms of improvement effects, the mean shear strengths of FCS and SCS relative to the clay specimen are three and seven times greater, respectively, for a replacement area ratio of 49%.