These piles also transfer theirload to the around through skin friction.the of driv such piles does not c ompact the soi app types of pile foun ndations 1.4.6 Combination of friction piles and cohesion piles An extension of the end bearing pile when the bearing stratum is not hard, such as a firm clay.The pile is driven far enough into the lower material to develop adequate frictional resistance.a farther variation of the end bearing pile is piles eas.This is achieved by forcing a bulb of concrete into the soft stratum immediately above the firm layer to give an enlarged base.A similar effect is produced with bored piles by forming a large cone or bell at the bottom with a special reaming tool.Bored piles which are provided with a bell have a high tensile strength and can be used as tension piles (see fig.1-3) able so 60° Figure 1-3 under-reamed base enlargement to a bore-and-cast-in-situ pile 1.4.7 Classification of pile with respect to type of material 。Timber Concrete 。Steel Composite piles 1.4.8 Timber piles Used from earliest record time and still used for permanent works in regions where timber is plentiful.Timber is most suitable for long cohesion piling and piling beneath embankments.The timber should be in a good condition and These piles also transfer their load to the ground through skin friction. The process of driving such piles does not compact the soil appreciably. These types of pile foundations are commonly known as floating pile foundations. 1.4.6 Combination of friction piles and cohesion piles An extension of the end bearing pile when the bearing stratum is not hard, such as a firm clay. The pile is driven far enough into the lower material to develop adequate frictional resistance. A farther variation of the end bearing pile is piles with enlarged bearing areas. This is achieved by forcing a bulb of concrete into the soft stratum immediately above the firm layer to give an enlarged base. A similar effect is produced with bored piles by forming a large cone or bell at the bottom with a special reaming tool. Bored piles which are provided with a bell have a high tensile strength and can be used as tension piles (see fig.1-3) Figure 1-3 under-reamed base enlargement to a bore-and-cast-in-situ pile 1.4.7 Classification of pile with respect to type of material • Timber • Concrete • Steel • Composite piles 1.4.8 Timber piles Used from earliest record time and still used for permanent works in regions where timber is plentiful. Timber is most suitable for long cohesion piling and piling beneath embankments. The timber should be in a good condition and