Excavation

1. Excavation Lesson 3 M. S. Martin Sept 2009

2. De - Watering • The removal of ground water and / or accumulated rainwater from within excavations or earthworks by means of mechanical pumps. Usually to enable continuation of work.

3. Typical Footings

9. Shoring

10. Shoring or Trench Support • Manually or mechanically excavated trenches over 1.5m in depth require some form of support for the sides, to prevent possible collapse, while working in the trench. • This is typically done by benching battering or ‘shoring’. • Open or closed support systems are available in timber, steel or combinations of both.

11. Shoring – Add definition to P. 31 • Trench support to sides of excavations to prevent possible collapse, typically trenches over 1.5m deep, must be benched, battered or ‘shored’.

12. Timber Shoring Poling boards Wedges Waling Bracket head of screw jack Waler Cleat Strut Waling hook Plate head Bevelled ends OPEN TIMBERING OPEN METAL SHEETING

13. Timber Shoring

15. Report if you see any of the following Next two slides from J. Bridges (SWSI) slides on shoring & trenching

16. Warning Signs • If you notice any of the following situations, take remedial action and/or notify your supervisor immediately. Subsidence alongside trench Waterentering trench

17. Warning Signs - Cont’d Earth Fretting from sides Tension Cracks Deflection in Shoring Excessive creaking in shoring

18. Surface & Sub-Surface Drainage: P. 20 • It is a mandatory Local Council requirement • to prevent surface eroded surface materials ending up in the street gutters and storm water pits/drains • These fences may be constructed of • Polypropylene (shade cloth) • Straw bales • Geotech fabrics, etc. Drainage area 0.6ha. max Slope gradient 1:2 max. Slope length 60m max. Geotextile filter fabric DISTURBED AREA Posts driven 0.6 into ground 3000 max. 600mm UN-DISTURBED AREA 200mm SEDIMENT FENCE

20. Types of Drainage • Surface Drains • Dish Drains • Rubble Drains • Sub-surface drains

22. Cut & Fill Sites – P. 21 • these types of sites need to have sufficient consideration to ensure adequate site drainage, and will typically use all of the drainage types mentioned above.

23. Slabs • Types: • Slab on ground, basic garage, paths • Raft Slab • Waffle slab • Stiffened Raft • Any others ?

24. Stiffened Raft

25. Waffle Slab

26. Slab Calc’s

28. Volume Slab • Break the slab into two areas, i.e. the slab and the thickened splayed edge beam. Firstly, calculate the volume of the slab; • L x W x T =7.5x3.8x0.1 =2.850m³

29. Volume Beam • The simplest way of calculating the beam is to calculate the average area of the beam section and multiply it by the centre line length of the beam • L x W • 0.350 x 0.100 = 0.035m² • Now calculate the centre line length of the beam

30. Beam Length Now multiply the average beam area by the average length to calculate the volume of the beam; Area x Length 0.035x21.200 0.742m³

31. Totals • To calculate the total volume of concrete in the slab and the beam, add the two separate volumes together; • Volume of slab + Volume of beam 2.850+0.742 = 3.592m³ • ORDER - 3.6m³ of concrete