The document discusses different methods for excavation support and retaining walls, including soldier beams and lagging, sheet piling, soil nailing, tiebacks, and ground freezing. It provides examples and diagrams to illustrate soldier beams and lagging, bracing for shallow trenches, soil nailing, raker bracing for wide excavations, tied-back concrete walls, and tieback installation. It also provides more detail on ground freezing, describing it as a technique used for over 100 years for groundwater control and excavation support by circulating refrigerant through subsurface pipes to freeze soil and create a strong, watertight material.

1. earth supports

2. Use of plastic sheets for slope protection in a shallow excavation

4. E A R T H W O R K S U P P O R T S TIMBER PLANKING TIMBER SOLDIERS

5. E A R T H W O R K S U P P O R T S STEEL SOLDIER PILES TIMBER PLANKING

6. E A R T H W O R K S U P P O R T S

7. Excavation supports using soldier beam and lagging.

8. Two examples of soldier beams and lagging method used for retaining walls

9. Two examples of soldier beams and lagging method used for retaining walls

10. Examples of soldier beams and lagging method used for retaining walls

11. STEEL SHEET PILING

12. E A R T H W O R K S U P P O R T S

13. STEEL SHEET PILES

14. E A R T H W O R K S U P P O R T S STEEL SHEET PILES

15. Bracing for shallow trenches (a) intermittent sheeting and bracing

16. Bracing for shallow trenches. (b) continuous sheeting and bracing,

17. Bracing for shallow trenches. (c) trench shielding

18. A typical trench box

19. Soil Nailing Examples

20. Soil Nailing Examples

21. Soil Nailing Examples

22. Schematic diagram of narrow excavation bracing

23. Internal struts

24. Support for Rakers

25. Raker bracing for wide excavations

26. Excavation sub-grade Ground surface Grout or transfer materials Stressing unit Sheeting Tendon 10-20 0 Bond free zone Assumed surface of sliding wedge Tieback installed at 10 to 20° down from horizontal

27. Tied-back concrete wall constructed underground for excavation support

28. Tieback being installed

29. Tieback Examples

31. GROUND FREEZING

32. Ground freezing is a technique that has been used extensively for groundwater control and excavation support in the underground construction industry for over 100 years.

33. The process involves the circulation of a refrigerated coolant through a series of subsurface pipes to convert soil water to ice, creating a strong watertight material. The material is so strong, in fact, that it is routinely used as the only method of groundwater control and soil support for the construction of shafts hundreds of feet into water-bearing soils.

34. Most ground freezing systems are quite similar in principal. The single most important co mponent of a ground freezing system is the subsurface refrigeration system , consisting of a series of refrigeration pipes installed with various drilling techniques. Depending upon the application, the coolant can be brought to temperatures well below -150 degrees celcius Ground freezing can be achieved by using either a large portable refrigeration plant or liquid nitrogen . After the initial freezing has been completed and the frozen barrier is in place, the required refrigeration capacity is significantly reduced to maintain the frozen barrier.