Topic 4.1.2 Flashcards
Properties of H-piles
Relatively light, easy to handle and drive
Splicing can be carried out by site welding
Has small displacement and suitable for driving in groups at close centres where ground heave or lateral displacement has to be avoided
Where is H-piles used
In conjunction with marine structures and
Where overlying soil is very weak
What size do H-piles come in
200mm-400mm
6m and 12m in length
What is the structural capacity of an H-pile
40 tonnes-1000 tonnes
How are H-piles installed
Hydraulic hammer
Jack-in
Steps of installing H-pile
- Hoisting pile into position
- Driving pile
- Jointing
- Inspection of joint
- Cutting of piles
Purpose of sheet piles
Construction of retaining walls
Protection from river bank erosion
Retain loose soil around foundation trenches
Isolation of foundation from adjacent soils
Properties of bakau piles
Cheap and easy to install
Only used in soft soil and always below water level
What is the structural capacity of bakau piles
1 tonne per bakau pile
What size do bakau piles come in
75mm in diameter
5m in length
What is a pile set
Distance that a pile is driven into the ground by a single blow of the hammer
When are pile sets measured
Final stage of piling
How are driven piles installed
Diesel / Hydraulic / Drop hammer
Jacked-in
Pre-bore then drive
Pre-bore then jacked-in
Describe diesel hammer driving
Ram raised by explosive mixture of diesel/air
Noisy/inefficient
Increasingly replaced by hydraulic hammer
Describe hydraulic hammer driving
Ram is raised hydraulically
More efficient
Quieter
Describe jacked-in installation
Pressed into soil by means of static force
Properties of jacked-in installation
Max force = 7000kN
Width of machine = 13.5m
Max pile diameter = 600mm
Advantages of jacked-in installation
Low noise and vibration
Faster construction rates
Cleaner sites
Disadvantages of jacked-in installation
Strong and flat piling platform required
Larger working area required
Limited pile size
Unable to go through boulders/hard layers
What do vibratory hammers do
Used for driving and extracting H-piles, sheet piles and steel tube piles
Describe pre-boring
To loosen the soil so that less energy is required when driving the piles and it is carried out by augering
Advantages of driven piles
Can be precast to required specifications
Work is neat and clean
Piles of any size, length and shape can be made in advance and used at the site
Most favoured for works over waterD
Disadvantages of driven piles
Piles must be properly reinforced to withstand handling stress during transportation and driving
Advanced planning is required for transportation and driving
Have to cut or add extra lengths which increases project cost
