Basement & Waterproofing

Lecture Outline

1. What can basements be used for?

So, basements can provide ............space in

a building and thereby enhancing the

............. of occupants.

additional

quality of life

What are the loads that are acting on a

basement?

What are the issues arising during

excavation works?

1.What are you going to find during excavation

2.Temporary/permanent soil support

3.Keeping the water out!

3. Methods for basement construction

Open excavation

Bored pile walls (Contiguous Piling )

Diaphragm Walling

Open excavation

Open excavation

• Using open excavation with temp support usually

steel sheet piles

• Sides being battered to angle of repose

• Construction is carried out and then …

• Backfill after construction

Interlocking sheet piling

Interlocking sheet piling • Interlocking steel sheet piles driven

into ground

• To obtain continuous barrier in the

ground so that permanent work can

proceed

Methods

• Sheet piles driven into ground

• Excavation between steel sheet

piling in stages

• Ground anchors installed at

regular intervals

• Excavation to formation level

• Basement construction

• Steel sheet can either be

withdrawn or left in as permanent

ground water control

Interlocking sheet piling

Advantages

• Watertight

• Safe

• Quick

• Suitable for

congested site

• Suitable for deep

excavation

• Simple, less

obstruction

• Suitable for most

soil types

Disadvantages

• Noisy

• Not economical for

big one-off project

Drilling rig

Bored Piling

• Similar to

diaphragm wall

• Closely spaced

precast/ bored

piles are used to

form perimeter

retaining walls

• Diameter varies

from 300-600 mm

Bored Pile walls

piling rig in Continuous

Flight Auger (CFA)

mode

The range of CFA piles is between

300mm and 1200mm in diameter and

can be created up to 30 meters long.

Rotary Bored Piling

piling rig in rotary bored piling

mode

For larger diameter piles up to

3000mm rotary flight auger systems

can be used, but these are not

continuous flight and the soil has to be

brought to the surface in sections.

Diaphragm Walls

Diaphragm walls are typically 20m to 50m deep, but may extend to

considerably greater depth.

Retaining walls construction

www.bacsol.co.uk

Diaphragm

walls

www.bacsol.co.uk

Diaphragm Walls

Retaining walls construction

Advantages • Watertight

• No underpinning of adjacent

properties necessary

• No noise / vibration problem

• For congested site

• For deep excavation

• Min.movement of pavement,

road and services

• Can form part of basement

structure

Disadvantages

• Mud sediment at trench base might

not be displaced completely by

concrete

• Finished walls in gravel soils

expected to be rough

• Uncertain quantity of concrete

needed

• Larger tolerance of concrete cover

is necessary

• Concrete to be placed continuously

to avoid trapping mud in the body of

wall

• Construction is slow / can be

expensive

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Responsibilities for safety, quality and the environment

Risk management

Working platforms

Pile trimming

Essential design requirements

Ground conditions

Workmanship

What are the ICE Health and Safety

specifications for piling and retaining walls work?

3. Waterproofing

The image below shows various water penetration points. Nearly every one

of these are present in the modern basement in some form or another.

What are the signs of water seepage

through a basement?

Internal tanking

Tanking is applied to the inside face of the slab and walls.

External

tanking

• Waterproof membrane materials:

– Mastic asphalt

– Polythene sheeting

– Bituminous compound

– Epoxy resin

– Bitumen laminates

Tanking Method

Eg of Page 11 – Basement Waterproofing Details

Cross Section

– Use Tanking Method

Eg of Page 11 – Basement Waterproofing Details

Cross Section

– Use Tanking Method

Example of Pile Layout Plan