Lecture14-Types-of-Deep-Foundations

Lecture14-Types-of-Deep-Foundations - Foundation...

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Unformatted text preview: Foundation Engineering Foundation Engineering Lecture #14 Lecture #14 Types of Deep Foundations- Timber piles- Reinforced Concrete piles- PIFs- Steel piles- Composite piles- Augercast shafts- Drilled shafts L. Prieto-Portar 2009 Surface soils with poor bearing may force engineers to carry their structural loads to deeper strata, where the soil and rock strengths are capable of carrying the new loads. These structural elements are called deep foundations . The oldest known deep foundation was a pile . Originally, piles were simply tree trunks stripped of their branches, and pounded into the soil with a large stone, much like a carpenter hammers a nail into a wooden board. Pile driving machines have been found in Egyptian excavations, consisting of a simple "A" frame, a heavy stone and a rope. Roman military bridge builders used a similar technique. Both were early examples of driven piles. In 1740 Christopher Phloem invented pile driving equipment using a steam machine which resembles todays pile driving mechanisms. This method evolved by using steam to raise the weights (in lieu of human power) during the late 1800s, and then diesel hammers were developed in Germany during WWII. The most recent advance in pile placing is the hydraulic hammer. Steel piles have been used since 1800s and concrete piles since about 1900. In contrast, shafts or placed deep foundations are screwed (augered) into the soil, much like a carpenter places a screw into a wooden board. Similarly to the contrast between nailing versus screwing, the shafts are usually a quiet operation that tends to improve the soil and rock texture to carry the load. They have larger load capacities and are cheaper per unit load carried. Roman military engineers developed pile hammers that could vary the angle of batter. This is the method employed by Julius Caesar in crossing the Rhine in 52 BC. The purpose of a deep foundation is to transmit the structural loads to a stratum that is capable of providing both bearing capacity and acceptable settlements. The deep foundation must be also capable of resisting vertical compressive, lateral and uplift loads. Piles are commonly used for, 1. To carry structure loads into or through a soil stratum. 2. To resist uplift or overturning forces. 3. To control settlements when spread footings are on marginal or highly compressible soil. . o control scour problems on bridge abutments or piers. 4. To control scour problems on bridge abutments or piers. 5. In offshore construction to transmit loads through the water and into the underlying soil. 6. To control earth movements, such as landslides. Piles are inserted into the soil by the following methods: 1. Driving using a pile hammer....
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This note was uploaded on 09/07/2011 for the course CEG 4012 taught by Professor Staff during the Spring '10 term at FIU.

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Lecture14-Types-of-Deep-Foundations - Foundation...

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