日 Figure 1-5 Hercules typeof pile joint 1.4.10 Driven and cast in place Concrete piles Two ofthe main types used in the UK are:West's shell pile:Pre cast. reinforced concrete tubes,about 1 m long,are threaded on to a steel mandre and driven into the ground after a concrete shoe has been placed at the front of the shells.Once the shells have been driven to specified depth the mandrel is withdrawn and reinforced concrete inserted in the core.Diameters vary from 325to600mm. Franki Pile:A steel tube is erected vertically over the place driven,and about a metre depth of gravel is placed atthed drop hammer,1500 to 4000kg mass,compacts the aggregate into a solid plug which then penetrates the soil and takes the steel tube down with it.When the required depth has been achieved the tube is raised slightly and the aggregate broken out.Dry concrete is now vadded and hammered until a bulb is formed. Reinforcementis place med until the pile top comes up to ground levels placed an ed in position and more
Figure 1-5 Hercules type of pile joint 1.4.10 Driven and cast in place Concrete piles Two of the main types used in the UK are: West’s shell pile : Pre cast, reinforced concrete tubes, about 1 m long, are threaded on to a steel mandrel and driven into the ground after a concrete shoe has been placed at the front of the shells. Once the shells have been driven to specified depth the mandrel is withdrawn and reinforced concrete inserted in the core. Diameters vary from 325 to 600 mm. Franki Pile: A steel tube is erected vertically over the place where the pile is to be driven, and about a metre depth of gravel is placed at the end of the tube. A drop hammer, 1500 to 4000kg mass, compacts the aggregate into a solid plug which then penetrates the soil and takes the steel tube down with it. When the required depth has been achieved the tube is raised slightly and the aggregate broken out. Dry concrete is now added and hammered until a bulb is formed. Reinforcement is placed in position and more dry concrete is placed and rammed until the pile top comes up to ground level
1.4.11 Steel piles Steel piles:(figure 1.4)steel/Iron piles are suitable for handling and driving in long lengths.Their relatively small cross-sectional area combined with their high strength makes penetration easier in fimm soil.They can be easily cut off or joined by welding.If the pile is driven into a soil with low pH value,then there is a risk of corrosion,but risk of corrosion is not as great as one might think. ugh tar coating or cathodicprotection can be employed in permanent works It is common to allow for an amount of corrosion in design by simply over dimensioning the cross-sectional area of the steel pile.In this way the corrosion process can be prolonged up to 50 years.Normally the speed of in design,this value can be taken as X工 a)X- b)H- cross-section cross-section steelpipe Figure 1-6 Steel piles cross-sections 1.4.12 Composite piles Combination of different materials in the same of pile.As indicated earlier,part of a timber pile which is installed above ground water could be vulnerable to insect attack and decay.To avoid this,concrete or steel pile is used above the gaen8e"edlhiodplesnsledunderhegroundwaerad
1.4.11 Steel piles Steel piles: (figure 1.4) steel/ Iron piles are suitable for handling and driving in long lengths. Their relatively small cross-sectional area combined with their high strength makes penetration easier in firm soil. They can be easily cut off or joined by welding. If the pile is driven into a soil with low pH value, then there is a risk of corrosion, but risk of corrosion is not as great as one might think. Although tar coating or cathodic protection can be employed in permanent works. It is common to allow for an amount of corrosion in design by simply over dimensioning the cross-sectional area of the steel pile. In this way the corrosion process can be prolonged up to 50 years. Normally the speed of corrosion is 0.2-0.5 mm/year and, in design, this value can be taken as 1mm/year a) Xcross-section b) H - cross-section c) steel pipe Figure 1-6 Steel piles cross-sections 1.4.12 Composite piles Combination of different materials in the same of pile. As indicated earlier, part of a timber pile which is installed above ground water could be vulnerable to insect attack and decay. To avoid this, concrete or steel pile is used above the ground water level, whilst wood pile is installed under the ground water level (see figure 1.7)
Concrete pi Woodpile Lowest ground b) Figure 1-7 Protecting timber piles from decay: a)by pre-cast concrete upper section above water level b)by extending pile cap below water level 1.4.13 Classification of pile with respect to effect on the soil A simplified division into driven or bored piles is often employed 1.4.14 Driven piles Driven piles are considered to be displacement piles.In the process of driving the pile into the ground,soil is moved radially as the pile shaft enters the gechdnhemeyalsobeacomponentotnmo,ementoithesalnheueted
Figure 1-7 Protecting timber piles from decay: a) by pre-cast concrete upper section above water level. b) by extending pile cap below water level 1.4.13 Classification of pile with respect to effect on the soil A simplified division into driven or bored piles is often employed. 1.4.14 Driven piles Driven piles are considered to be displacement piles. In the process of driving the pile into the ground, soil is moved radially as the pile shaft enters the ground. There may also be a component of movement of the soil in the vertical direction
DRIVEN PILES CASED SHELL-LESS Figure 1-8driven piles 1.4.15 Bored piles Bored piles(Replacement piles)are generally considered to be non-displacement piles a void is formed by boring or excavation before piles is since the bore hole walls do not requires temporary support except cloth to the ground surface.In unstable ground,such as gravel the ground requires temporary support from casing or bentonite slurry.Altemnatively the casing may be permanent,but driven into a hole which is bored as casing is advanced.A diferentechniaue which is still essentially no -displacement,is to intrude grout or a concrete from an augerwhich is rotated into the granular soil,and hence produced a grouted column of soil. There are three non-displacement methods:bored cast-in-place piles, particularly pre-formed piles and grout or concrete intruded piles. The following are replacement piles Augered Cable percussion drilling Large-diameter under-reamed
Figure 1-8 driven piles 1.4.15 Bored piles Bored piles(Replacement piles) are generally considered to be non-displacement piles a void is formed by boring or excavation before piles is produced. Piles can be produced by casting concrete in the void. Some soils such as stiff clays are particularly amenable to the formation of piles in this way, since the bore hole walls do not requires temporary support except cloth to the ground surface. In unstable ground, such as gravel the ground requires temporary support from casing or bentonite slurry. Alternatively the casing may be permanent, but driven into a hole which is bored as casing is advanced. A different technique, which is still essentially non-displacement, is to intrude, a grout or a concrete from an auger which is rotated into the granular soil, and hence produced a grouted column of soil. There are three non-displacement methods: bored cast- in - place piles, particularly pre-formed piles and grout or concrete intruded piles. The following are replacement piles: Augered Cable percussion drilling Large-diameter under-reamed
Types incorporating pre caste concrete unite Drilled-in tubes Minipiles 1.5 Aide to classification of piles Figure 1-8.for a quick understanding of pile classification,a hierarchical representation of pile types can be used.Also advantages and disadvantages of different pile materials is given in section 1.6
Types incorporating pre caste concrete unite Drilled-in tubes Mini piles 1.5 Aide to classification of piles Figure 1-8. for a quick understanding of pile classification, a hierarchical representation of pile types can be used. Also advantages and disadvantages of different pile materials is given in section 1.6