Abstract
Problematic soils exist almost everywhere on the globe. State-of-the-art solutions to make civil engineering infrastructures built on them are still highly sought. The CFG (cement-fly ash-gravel) pile composite foundation system has been widely used in buildings, highways, railways, and bridge transition sections owing to its proven engineering characteristics in soft ground treatment. This paper discusses about the development and achievements of its engineering applications, along with possible future research directions. The remarkable evolution took place in the past to address projects’ strict differential and postconstruction settlement control requirements including embedding the geosynthetic layer into the load transfer platform and combining it with rigid slabs, as seen implemented in few CFG pile-supported embankments. It was also observed that the interaction of the existing CFG pile composite foundation with an adjacent new foundation pit excavation inevitably presents a complex soil-structure interaction mechanism among the fundamental components—the retaining wall, mat, piles, cushion, and soil.
Highlights
Consumption of industrial wastes as dust and/or aggregate in geotechnical application is developing globally
Ash-gravel (CFG) piled composite foundation is a part of it where the by-product fly ash is used as a constituent material to improve poor engineering properties of soft or weak foundation soils using column technology
Steel reinforcing bars are not usually needed inside the pile, and the industrial waste-fly ash is used as an admixture for the concrete [6]. e akin column technology commonly used to improve the soft ground in the USA is termed as “rammed aggregate piers.”
Summary
Consumption of industrial wastes as dust and/or aggregate in geotechnical application is developing globally. Remarkable research works have experimentally, analytically, and numerically been carried out to comprehend the mechanism of interaction among the soil, pile, and supported structure in the CFG pile composite foundation system [16,17,18,19,20,21]. E pile-soil stress ratio is an important reflection parameter for the working condition of the CFG pile composite foundation. Boussetta et al [35] investigated the cushion thickness effect on the pile-soil stress ratio for a rigid and flexible foundation system. Zhang and Zhang [49] experimentally studied CFG piles combined with vibroreplacement stone columns All these multipile composite foundations emerged to fulfill the need for modifying the rigidity and stability of the poor subsoil as well as drainage requirements to accelerate excess pore water pressure dissipation. It is noteworthy that none is omnipotent by itself but has a certain application scope as far as any soft ground treatment method is concerned
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