BEARING CAPACITY OF SHALLOW FOOTING ON SOFT CLAY IMPROVED BY COMPACTED FLY ASH

Abstract

Low bearing capacity of weak soil under shallow footings represents one of construction problems.
Kaolin with water content converges to liquid limit used to represent the weak soil under shallow
footing prototype. On the other hand, fly ash, which can be defined as undesirable industrial waste
material, was used to improve the bearing capacity of the soft soil considered in this research. The soft
soil was prepared in steel box (36×36×25) cm and shallow square footing prototype (6×6) cm were
used .Group of physical and chemical tests were conducted on kaolin and fly ash. The soft soil was
improved by a bed of compacted fly ash placed under the footing with dimensions equal to that of
footing but with different depth ratios. The results show that there is a noticeable improvement in the
behavior of footing when improved by compacted fly ash. The improvement showed a decrease in
settlement and increase in bearing capacity. The improvement ratio in bearing capacity was calculated
by comparing the ultimate bearing capacity value when testing the kaolin alone with its value of kaolin
improved with compacted fly ash at the same value of eccentricity. It is important to note that
eccentricity values were chosen according to the rule of middle third of footing base(i.e.,e≤B/6). The
improvement ratio was about (130%) in average value, that represent a good ratio of improvement