PILE FOUNDATIONS Dr. Tin Tun ( 03-08-2014 ) 5:20 am Piles are relatively slender shafts, cylindrical in shape, driven or bored into the ground to the required depth. Piles are used to carry vertical loads through weak soil to dense strata having high bearing capacity. In normal ground conditions, they can resist large uplift and horizontal loads, hence can be used as foundations of multistoried buildings, transmission line towers, retaining walls, bridge abutments. Pile foundations are the part of a structure used to carry and transfer the load of the structure to the bearing ground located at some depth below ground surface. The main components of the foundation are the pile cap and the piles. Piles are long and slender members which transfer the load to deeper soil or rock of high bearing capacity avoiding shallow soil of low bearing capacity The main types of materials used for piles are Wood, steel and concrete. Piles made from these materials are driven, drilled or jacked into the ground and connected to pile caps. Piles are classified depending upon type of soil, pile material and load transmitting characteristics. Pile foundations have been used as load carrying and load transferring systems for many years.In the early days of civilization from the communication, defence or strategic point of view villages and towns were situated near to rivers and lakes. It was therefore important to strengthen the bearing ground with some form of piling. Timber piles were driven in to the ground by hand or holes were dug and filled with sand and stones. In 1740 Christoffoer Polhem invented pile driving equipment which resembled to days pile driving mechanism. Steel piles have been used since 1800 and concrete piles since about 1900. The industrial revolution brought about important changes to pile driving system through the invention of steam and diesel driven machines.More recently, the growing need for housing and construction has forced authorities and development agencies to exploit lands with poor soil characteristics. This has led to the development and improved piles and pile driving systems. Today there are many advanced techniques of pile installation Function of piles As with other types of foundations, the purpose of a pile foundations is: a) to transmit a foundation load to a solid ground b) to resist vertical, lateral and uplift load A structure can be founded on piles if the soil immediately beneath its base does not have adequate bearing capacity. If the results of site investigation show that the shallow soil is unstable and weak or if the magnitude of the estimated settlement is not acceptable a pile foundation may become considered. Further, a cost estimate may indicate that a pile foundation may be cheaper than any other compared ground improvement costs. In the cases of heavy constructions, it is likely that the bearing capacity of the shallow soil will not be satisfactory, and the construction should be built on pile foundations. Piles can also be used in normal ground conditions to resist horizontal loads. Piles are a convenient method of foundation for works over water, such as jetties or bridge piers. ီ
Posted on: Sat, 02 Aug 2014 23:48:26 +0000
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