Support Of Vertically Sided Excavations Flashcards
Define cofferdam
A retaining wall structure to facilitate construction within it
Name the 6 site investigations that determine excavation support
Ground conditions
Depth of excavation
Ground water table level
Location
Proximity to to other structures
Specialised skills
What is continuous piling?
When the piles have small gaps between them
What is secant piling?
When piles are interlocked in a pattern of reinforced the not reinforced
In what order are secant bored piles constricted?
Construct soft circular non reinforced piles then cut harder reinforced piles into them
What are the advantages of bored secant walling?
Water retaining
High lateral resistance
Load bearing
High tolerances with guide walls
What are the disadvantages of bored secant walling?
Expensive
What are the three ways sheet cofferdams can be supported?
Internally anchored/propped
Externally anchored
Cantilevered
What are the three methods of installation of sheet steel piling?
Pitch and drive
Panel driving
Pushed in
What are the advantages of pitch and drive?
Resonance hammer has a capacity of 100 tonnes
Rigs install up to 18m piles
Less noise due to high load capacity
No need for guide frames
Computer assisted installation and modelling
What is panel drive?
When piles are installed within a guide frame using a high frequency suspended from a crane in marine projects
What is push in and where is it used?
Residential areas as it’s silent and vibrationless
Difficult ground can be dealt with using pre angering or water jetting
The rig walks along a row of steel sheet piles
What are the 7 stages of cofferdam construction?
1) clear and level work area
2) ensure support materials and plant are ready
3) set up pile guide frame
4) drive piles to full depth
5) install dewatering
6) 1st stage excavation to install frame
7) complete excavation
Name 5 risk management issues of cofferdam construction
Open excavation
Prevention of falls
Safe access to base of excavation
Protection of work force in excavation monitor support frames
Noise from sheet piling
Disposal of groundwater and excavated material
