Excavation, week 2

M. S. MartinSept. 2009

Classification of SoilsThis and next four slides from Build Right - toolbox

• Site classification• Soils are classified

according to their stability. • Soil samples are taken on

the site to determine soil class.

• A geotechnical engineer's report will clearly state the likely soil conditions and recommend a suitable footing system.

Site Classification Acceptable Standards book P 17 Type of soil Description Class

Rock Rock sites have no ground movement

A

Sand Sand has little or no movement

A

Clay, slightly reactive

Slight ground movements due to moisture changes

S

Clay, moderately

reactive

Moderate ground movements due to moisture changes

M

Clay, highly reactive

High ground movements due to moisture changes

H

Clay, extremely reactive

Extreme ground movements due to moisture changes

E

Problem Sites which include soft soils, loose sands,

landslip, mine subsidence, collapsing soils, erosion, fill and abnormal moisture

conditions

P

Volume changes in soil

• The effects of volume changes in soil

• Volume changes result in possible serious damage to the footings or to the building they support.

• The footing system must be selected to suit the anticipated volume change of the foundation soil.

Wet soil - volume increases

Dry soil - volume decreases

Bearing Pressure

• The bearing pressure of foundation soils

• Soils are measured for their allowable bearing pressure.

• The allowable bearing pressure is the soil's ability to carry the load of a building and its contents without excessive settlement.

For one and two-storey buildings, the Building Code of Australia (BCA) requires a minimum bearing pressure of only:

100 kPa for under strip and pad footing systems 50 kPa for under slab footings.

Review Profiles

Profiles continued

• Strip Footing, Brick Veneer Construction– Outside of footings– Outside brick veneer skin

• Slab on Ground, timber frame– Outside slab & wall (same)

Dial before you dig – P. 9• Digging Safely You cannot be too careful

when it comes to safe excavation.• Avoiding underground pipe and cable

damage is as simple as having the right tools, the right skills and the right information.

• Each asset owner can provide information on their requirements in regard to safe digging practices. This may include manually exposing the network. Simply contact the asset owner to find out how to work safely around their underground networks. Their contact details will be found on the Confirmation Sheet you receive from Dial Before You Dig or on the information your receive from the asset owner.

• In the planning stages of building and construction for every project you need to obtain underground network information - lodge your enquiry online now .

Major Utilities – P. 9

• Energy Australia• Integral Energy• Telstra• Optus• AGL• Sydney Water

• Any others ?

Hazard Identification & Risk Assessment – P 9

Identify the Hazard

Assess the Risk (s), arising from the hazards

Use appropriate control measures, to eliminate or reduce the risk (s)

Monitor & review the control measures to ensure continual safety

Descriptions – P. 10

• Batter – Where the wall of an excavation is sloped back to a pre-determined angle

• Benching – This is the creation of stepped sides to an excavation by forming a number of horizontal & vertical planes forming a number of steps in the wall of the excavation.

• Pictures next slide

Add New Terminology - 31

• Angle of Repose - the angle of repose is the natural angle a pile of material forms with the ground, when loose & un-weathered

• Bulking – The increase in the bulk volume of material, once excavated from the ground. When excavated it increases in size, by including pockets of air (now un-compacted)

• Moisture also adds volume to soil ie: reactive clays

Bulking FactorsFrom: http://www.engineeringtoolbox.com/soil-rock-bulking-factor-d_1557.html

MaterialDensity at the Borrow(kg/m3)

Bulking Factor(%)

Basalt 2.4 - 3.1 75 - 80Clay 1.8 - 2.6 20 - 30Dolomite 2.8 50 - 60Gneiss 2.69 75 - 80Granite 2.6 - 2.8 75 - 80Gravel, dry 1.80 20 - 30Gravel, wet 2.00 20 - 30Limestone 2.7 -2.8 75 - 80Quartz 2.65 75 - 80Sand, dry 1.60 20 - 30Sand, wet 1.95 20 - 30Sandstone 2.1 - 2.4 75 - 80Slate 2.6 - 3.3 85 - 90Soil 1.2 - 1.6 20 - 30