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CE403 Construction Methodology

CE403 Construction Methodology. Rock Excavation. Rock Characteristics. Igneous Rock Sedimentary Rock Metamorphic Rock. Rock Characteristics. Igneous Rock Formed When the Earth’s Molten Material Is Cooled Homogeneous Most Difficult to Excavate Granite and Basalt. Rock Characteristics.

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CE403 Construction Methodology

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  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

  16. Soft Ground TBM

  17. 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.

  18. Jack-Leg Drill

  19. Percussion Eg. :Hydraulic Track Drill

  20. Rotary Blast Drill

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

  22. Drilling Rates (carbide bit)

  23. 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.

  24. Volume of Blasted RockRectangular Drill Pattern

  25. Figure 6-11Principal Drilling Patterns

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

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

  28. 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

  29. 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

  30. Rock Blasting Geometry and Symbols

  31. 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

  32. PreSplitting

  33. Rippers

  34. Ripper Production

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