Prestressed pipe pile is a hollow cylindrical elongated precast concrete member made by using prestressing technology and centrifugal molding method. It mainly consists of a cylindrical pile body, end plates and steel hoops. There are various piling methods for pipe piles. Our construction methods include hammering method, static pressure method, vibration method, water jetting method, pre-drilling method and center-digging method, among which the static pressure method is . commonly used. In recent years, in order to meet the needs of urban construction, large tonnage static compression piling machine has been developed to press prestressed pipe piles. Strictly speaking, CFG piles are not pile foundation, but foundation treatment technology.

　　CFG is the abbreviation of Cement Fly Ash Gravel, which means Cement Fly Ash Gravel Pile. It is a variable strength pile made of crushed stone, stone chips, sand, fly ash mixed with cement and water by various pile forming machines. By adjusting the cement content and mixing ratio, the strength grade of the pile can be changed from C5 to C25, which is a pile type between rigid and flexible piles.CFG piles work together with the soil between the piles to form a composite foundation of CFG piles through the bedding layer. Therefore, engineering design can be carried out according to the performance and calculation of composite foundation. In general, CFG piles do not need to calculate the amount of reinforcement, and industrial waste fly ash and stone chips can be used as admixture, which further reduces the project cost. According to the site conditions, the following construction techniques can be selected: long spiral drilled grouted piles, long spiral drilled pump grouted piles, vibrating immersed tube grouted piles.

　　Grouted piles refer to pile holes formed in foundation soil by mechanical drilling, steel pipe soil squeezing or manual digging, and reinforcement cage and concrete are placed in the pile holes. According to the different methods of hole formation, bored piles can be categorized into sunken piles, drilled bored piles and dug hole bored piles. Drilled piles are the pile type determined according to the classification of pile forming method.