This study presents the results of a series of monotonic undrained triaxial compression tests on clay specimens improved by columnar reinforcement. The process of loading and stress redistribution of a fly ash clay specimen (FCS), in comparison with a sandclay specimen (SCS), is examined in terms of stressstrain 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 found, predictably, that the deviator stress of the composite specimens was influenced by the consolidation stress, replacement area ratio, and properties of the column material. The stress concentration at the top of the composite ground which depends on the loading stage reaches a peak after the consolidation state and is reduced due to stress redistribution between the column 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%.Key words: composite ground, fly ash, soil improvement, soft ground, triaxial test.
Influence of cement-fly ash-gravel pile-supported approach embankment on abutment piles in soft ground
