Basement & Waterproofing

Lecture Outline

1. What can basements be used for?

So, basements can provide...space additional in a building and thereby enhancing the quality... of life of occupants.

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anchors installed at regular intervals Excavation to formation level Basement construction Steel sheet can either be withdrawn or left in as permanent ground water control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

Similar to diaphragm wall Bored Piling 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 Retaining walls construction Diaphragm walls are typically 20m to 50m deep, but may extend to considerably greater depth.

www.bacsol.co.uk Diaphragm walls

www.bacsol.co.uk

Retaining walls construction Diaphragm Walls 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

www.casagrandeuk.com/videos.htm

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

Tanking Method Waterproof membrane materials: Mastic asphalt Polythene sheeting Bituminous compound Epoxy resin Bitumen laminates

Eg of Page 11 Basement Waterproofing Details Cross Section Use Tanking Method

Example of Pile Layout Plan