Chapter 81 Types of bearing piles

Piles are slender, columnar foundation elements. They are most commonly designed, as discrete bearing piles, to transfer part or all of the vertical loading imposed by a structure through weak and compressible soils to competent and stable soils, or rock. This chapter describes the most commonly available types of bearing pile and discusses the methods of construction and the advantages and constraints of individual techniques. Other applications of piling are discussed in Chapters 83 Underpinning and 85 Embedded walls. Section 81.2 describes the plant and a range of methods used in the construction of bored piles, including rotary cast-in-place, continuous flight auger and displacement auger techniques. Brief discussion of some specialised techniques including under-reaming, base grouting, embedded columns and geothermal piles completes this section. Driven piling techniques including timber, segmental precast, prestressed precast and driven cast in situ concrete are described in section 81.3, along with steel H and box section piles and steel tube piles. A discussion of modern driven piling plant is set in a historical context. The impact of ground conditions, environmental aspects and particular construction issues such as drivability, installation control and the effects of pile driving on the ground are also discussed. Finally section 81.4 discusses the wide-ranging application of micro-piling techniques. Practical aspects of various construction methods are discussed, covering rotary case and auger, rotary duplex, rotary down-the-hole-hammer, rotary percussive, hollow-segmental-auger and driven micro-piling. The section is completed with discussions of the grouts used in micro-piling and the particular environmental, quality assurance and health and safety issues that apply.