INFLUENCE OF DISTANCE BETWEEN CEMENT-FLY ASH-GRAVEL PILES ON THE FOUNDATION TREATMENT IN VIETNAM

Abstract

According to the Vietnam government’s statistics, there are currently about 19 thermal power plants
in operation, annually emitting about 20 million tons of fly ash which is classified as hazardous waste. This causes
an urgent environmental problem. In the context of lack of construction materials, the research aiming at promoting
consumption of the fly ash through the application of CFG (cement - fly ash - gravel) pile - a type of pile using a
mixture of cement, fly ash, aggregate handles the foundation for construction, that may help to consume a part of
the fly ash. Experimental research in the laboratory and field has been conducted. In the laboratory, the authors
produced 126 samples of CFG pile mixtures and selected the optimal mixture which ensures the pile strength
greater than 10MPa while still using fly ash to replace the maximum adhesive. In the field experiment, the authors
performed to construct an experimental model with CFG piles under an embankment. Soil Pressure Cells and
Settlement Plate was set up to monitor the development and load transfer. This paper assessed the influence of the
distance between CFG piles on soft soil treatment. The optimal ratio of fly ash to cement in the mixture is from
20% to 35%, and the appropriate distance between the piles is from 4d to 6d (d- diameter of the pile). This can be
an effective solution for soft soil treatment because it is feasible in terms of price and construction time. Moreover,
this solution is also easy for quality control in Vietnam