Research And Application Of CFG Pile Compound Foundation

CFG pile is the abbreviation of Cement Fly-ash Gravel pile, a kind of high bond strength pile made of cement, fly ash, reduced stone, rock chips and sand, mixed with water. It can be used to form compound foundation together with inter-pile soil and cushion course.CFG pile boasts many merits, such as high construction speed, short construction period, easy-to-control quality and low engineering cost.In this paper, engineering properties of CFG pile are discussed in details. Load tests deal with the bearing capacity of cushion course and pile-soil stress ratio, while indoor compression tests deal with influence of blend ratio of fly ash in pile material on pile strength.Through the tests conclusions can be drawn as follows:Both thickness and properties of cushion course have a prominent influence on both bearing capacity of CFG pile compound foundation and pile-soil stress ratio, i.e., without a proper thickness the bearing capacity of cushion course can not function effectively;As the load increases, pile-soil stress ratio usually first decreases and then increases; As the thickness of connatural cushion course increases, pile-soil stress ratio gradually inclines to 1.0;For heterogeneous cushion courses of the same thickness, as the particle size increases, pile-soil stress ratio increases;When the composite strength grade is lower than C10 and the requirement of engineering period is not pressing, composite of high blend ratio of fly ash can be considered, which will have little influence on its design strength and dramatically reduce the use level of cement.When higher strength grade is required of the composite, water reducing agent should be applied and low quantity of fly ash should be incorporated, so that the composite strength can be enhanced to design value.At the end of the paper, common problems in engineering practice and countermeasures are studied and discussed, and engineering application of CFG pile is illustrated further in case study.