CE403 Construction Methodology

1. CE403Construction Methodology Rock Excavation

2. Rock Characteristics • Igneous Rock • Sedimentary Rock • Metamorphic Rock

3. Rock Characteristics • Igneous Rock • Formed When the Earth’s Molten Material Is Cooled • Homogeneous • Most Difficult to Excavate • Granite and Basalt.

4. Rock Characteristics • Sedimentary Rock • Formed by settlement of material from water or air • Highly Stratified With Many Planes of Weakness • Most Easily Excavated Type of Rock • Sandstone, Shale and Limestone

5. Rock Characteristics • Metamorphic Rock • Started Out As Igneous or Sedimentary • Changed Heat, Pressure or Chemical Action • In Between Igneous and Sedimentary Rock in Difficulty of Excavation • Slate, Marble and Schist

6. Rock Investigation • Relative Hardness • Moh’s Scale ~ from 1 (talc) to 10 (diamond) • As a rule, any rock that can be scratched by a knife blade( hardness ~ 5) can be easily excavated by ripping or other mechanical methods. • Harder rock materials required additional investigation.

7. Investigation Methods • Drilling • Excavating Test Pits • Seismic Measurements

8. Seismic Refraction Test

9. Test Data

10. Upper Layer Thickness

11. Test Data

12. The Traditional Method of Excavating Rock • Drilling Blast Holes • Loading Holes With Explosives • Detonating Explosives • Loading the Fractured Rock Into Haul Units With Power Shovels • Hauling the Rock Away in Trucks or Wagons

13. Other Methods of Excavating Rock • Use of tractor mounted rippers to loosen the rock • Reinforced scraper to load & haul loosened rock • Trench Machines

14. Tunneling • Hard Rock Tunnel – use TBM • Soft Ground Tunnel – Use Tunnel Shield

15. Tunneling Machines or Moles

19. Soft Ground TBM

20. Drilling Equipment • Percussion Drills • penetrate rock by impact action. • Rotary Drills • cut by turning a bit under pressure against the rock face. • Rotary-Percussion Drills • combines both actions.

21. Jack-Leg Drill

22. Percussion Eg. :Hydraulic Track Drill

23. Rotary Blast Drill

24. Drilling Rates • Dependent on: • Rock Hardness • Drill Type and Energy • Type of Drill Bit

25. Drilling Rates (carbide bit)

26. Drilling Pattern & Rock Yield • Need to Determine: • Hole size, depth, and spacing • Depends on: • Amount and type of explosive used for each hole • Rock type and soundness • Results: • Small holes closely spaced yield small rock particles, • Large holes widely spaced will yield large rock particles.

27. Volume of Blasted RockRectangular Drill Pattern

28. Figure 6-11Principal Drilling Patterns

29. Typical Drill Hole Spacing (Rectangular Pattern), ft

30. Explosives • Dynamite • Ammonium Nitrate in Fuel Oil (ANFO) • Slurries ~ Mixture of gels, explosives and water.

31. Ammonium Nitrate Explosives • Has replaced dynamite in the Construction Industry because of lower cost and ease of handling. • ANFO is easy to handle because it is liquid. Can be poured down a drilled hole. • Ammonium Nitrate Explosives are not water resistant

32. Detonators • Electric and Non-Electric Caps. • Electric Caps (EB) are more widely used • Available as instantaneous or with a time delay • Caps are used to initiate primers which in turn initiate the main explosion. • Primers may be small charges of high explosives or primacord which is a high explosive in cord form. • Stemming - inert material, which used to confine explosion and increase effectiveness

33. Rock Blasting Geometry and Symbols

35. Secondary Blasting • To break up boulders and oversized fragments. • Block Holing ~ conventional drilling and blasting techniques • Mud Capping ~ explosive charge on the surface and covered with inert material. More explosives, but much quicker. • Presplitting • Line Drilling

36. PreSplitting

38. Rippers

40. Ripper Production