underpinning Flashcards
(11 cards)
What is the main objective of most underpinning work?
To transfer the load carried by a foundation from its existing bearing level to a new level at a lower depth.
What are the reasons that may necessitate an underpinning operation?
- Uneven settlement
- Increase in loading
- Lowering of adjacent ground
What causes uneven settlement in a building?
Caused by uneven loading of the building, unequal resistance of the soil, action of tree roots, or cohesive soil settlement.
What might lead to an increase in loading that requires underpinning?
Addition of an extra storey or an increase in imposed loading due to a change of use.
What general precaution should be taken before commencing underpinning work?
Notify adjoining owners of proposed works giving full details and temporary shoring or typing.
What should be included in the detailed survey before underpinning work?
Survey of the site, the building to be underpinned, and any other adjoining or adjacent buildings or structures.
What should be done about cracks before starting underpinning?
Indicators or tell tales should be fixed over existing cracks to monitor any subsequent movements.
If settlement is the reason for underpinning, what investigation should be carried out?
A thorough investigation to establish the cause and any necessary remedial works before starting underpinning.
What should be done to the loads on the building before underpinning work starts?
Reduce the loads as much as possible by removing imposed loads from the floor and installing props or shoring.
What should be done with services near proposed underpinning works?
Identify, trace, carefully expose, support, and protect them as necessary.
Fill in the blank: The main objective of underpinning is to transfer the load carried by a foundation from its existing bearing level to a new level at a _______.
[lower depth]
