Comparative analysis on effectiveness of crushed aggregate and scoria gravel as columnar reinforcement material under raft foundation

Abstract

Scoria gravel is widely used as stabilizer material in road construction and concrete works. However, limited information regarding its performance as columnar stabilizing material has been reported. This study hence explores suitability of scoria gravel as columnar stabilizing material in compressible soils. Besides, comparative analysis to evaluate effectiveness of crushed aggregate columns (CAC) and scoria gravel columns (SGC) in improving deformation characteristics of clay ground was carried out by using finite element based numerical analysis. Compressible massive clay reinforced with CAC and SGC under building load was modeled to simulate the settlement attributes of the foundation material. The conducted numerical model considered both the floating and end bearing gravel columns. Finding of the study revealed that provision of floating SGC performs better than the crushed aggregate stone column in lessening vertical deformation of the clay foundation. However, the floating SGC did not result in significant improvement in lessening lateral deformation in comparison with group of CAC. Hence, application of granular piles as columnar reinforcing material in purely clay soil is not as effective as SGC from settlement reduction view point. Contrarily, the bridging effect of end bearing crushed aggregate pile is more pronounced than that of scoria gravel as the column material directly gets contact with stiff substratum. It can also be inferred from finding of the study that application of granular pile group suits well compressible grounds where stiffer strata is situated immediately at column tip.