03 Saftey in Excavation & Blasting

1. Safety in Excavation & Blasting operation By Umesh Chandra Swain

2. EXCAVATION Reference Standard IS 3764 : 1992

3. Excavation • Excavation. Any man made cut, cavity or depression in the earth’s surface formed by earth.

4. Excavation Hazards • Soil Collapse • Utilities • Hazardous atmospheres • Adjacent structures • Falls / Falling loads • Access / Egress • Vehicle traffic • Mobile equipment • Water accumulation • Cave-in

5. Prior to Excavation • Obtain a work permit • Check Ground / Soil condition • Check Ground / Surface Water • Check the Location of Water Table • check Under ground / Overhead utilities • Adjacent buildings • Dynamic load / Traffic

6. Soil Classification • Type A : • Clay, sandy clay, clay loam • Type B: • Angular gravel (similar to crushed rock), silt, silt loam, sandy loam • Type C: • gravel, sand, loamy sand,Submerged soil or soil from which water is freely seeping; or Submerged rock that is not stable

7. Preventing Soil Collapse Soil classification (Type a, b, or C) • Sloping • Benching • Placing a shield. • Shoring(Timber / Aluminum shoring • Sheet piling

8. Simple Sloping • Stable Rock : 900 • Type A - 3/4:1 530 Short term up to 12’ -630 Note :Greater than 20 feet deep shall be designed by a registered professional engineer.

9. Unsupported Vertically-Sided Lower Portion <8 ft Unsupported Vertically-Sided Lower Portion <12 ft Simple Sloping -Type A Soil

10. Supported or Shielded Vertically-Sided Lower Portion Simple Sloping -Type A Soil

11. Simple Sloping • Type B - 1:1 450 • Type C - 1½ :1 340 Note :Greater than 20 feet deep shall be designed by a registered professional engineer.

12. Benching • Type A • Type B (cohesive soil) • Type C

13. Basic components of shoring

14. TimberShoringInstallations REFER TO DESIGN ENGR.

15. Utilities Underground PERMIT SYSTEM

16. UNDER GROUND ABOVE GROUND EFFECTS OF UTILITIES

17. FIRE EXPLOSION EFFECTS OF UTILITIES

18. UTILITIES PREVENTION • Obtain work permit and get clearances from the concerned • Electricity • Water & Sewage Pipeline • Communication • Oil & Gas Pipe Line • Use Detectors ( for More Reliable)

19. Water Accumulation • Ground water • Surface water

20. Surface water accumulation PREVENTION: If excavation work interrupts the natural drainage of surface water • Diversion ditches, • Dykes • other suitable means to prevent surface water • Excavations subject to runoff from heavy rains require an inspection by a competent person to evaluate water accumulation hazards.

21. Hazardous Atmospheres Never Start Work if, • Oxygen Level less than 19.5 % • Permissible limit of the toxic gases exceeded. • More than 20 % of Lower Explosive Limit. PRECAUTIONS • Ventilation to over come the above said. • Blocking the source, incase of toxic and flammable gases. (Using other effective controls to reduce the level of atmospheric contaminants to acceptable levels)

22. Adjacent Structures • Ensure structure stability • Shoring • Bracing • Evaluation by Professional

23. FALLING LOAD • Gravity • Weight of soil pile • Weight of near by structures • Weight of personnel &equipment • Vibration PREVENTION • Never operate a construction equipment within 2.5 m from the edge of the excavation. • Stacking the material 1 Meter away from the edge of the excavation.

24. ACCIDENT

25. Access / Egress • Ladders • Ramps with soil with slope not more than 15o • Stairs cut on earth

26. Vehicle Traffic Control Measures • Traffic Management Plan • Traffic Control • Traffic Safety Vests • Fencing • Illumination

27. Traffic Management Plan • Width of the passage. • Radius of curve. • Clearance with the side by objects.

28. Traffic Control Device & Vest

29. Fencing • Hard Barrication shall be provided, in the fall prone areas and if depth is more • Physical barricades required always • Must be placed 2m away from excavation edge. • Standard fall protection required for vertical falls over 1.3m • Traffic diversions • Pedestrian walkway diversions

30. Caution Signs Barricades Reflective Cone

31. ILLUMINATION Temporary Lightings: • Sufficient Area Lighting. • Emergency Lighting with Power back up.

32. Excavation Inspections • Daily Inspections by Competent Person Start of shift, as needed, following rainstorms or other hazard-increasing event • Possible cave-ins • Protective system failure • Water accumulation • Hazardous atmospheres

33. Blasting operations • IS 4081 : 1986 • Explosive Act, 1884 • Explosive rules, 1983

34. What is Blasting • Blasting is the process in which, the high pressure to which the rock is exposed shatters the area and exposes the space beyond that to vast tangential stresses and strains. • The phenomena takes place under the influence of outgoing shock waves which travel in the rock at velocity of 3000-5000 meters per second.

35. Principle of Rock Blasting • A Blasting operation is constituted of three stages: • Compression: High velocity pressure waves create micro-fractures. • Reflection: Waves bounce back from the free face & convert into tensile & shear waves causing more fracture growth. • Gas Pressure: Large volume of high pressure gas expand the cracks

36. Hazards • Fly rock. • Misfire. • Fumes. • Dust. • Unintentional charging. • Friction developed during next drilling. • Smoking. • Radio frequency waves. • Lightning. • Static electricity.

37. Sequence of Operation • Drilling a hole • Inserting a charge, • Stemming (covering the charge with a dense material to prevent dissipation of the explosive force) • Firing (detonator or fuse)

38. Cross – section of Blasting Hole Detonating Fuse Stemming ( Sand, Clay or Mud ) * * * * * * * * * * Explosive Cartridge Primer Explosive Detonator

39. Drilling Pattern in Trenching

40. Pre-splitting • Row of holes drilled along the final excavation line. • Holes loaded with light charge prior to the main blast causes a fracture. • Fracture generates a discontinuity which minimize the Over-break & produces a smooth finished wall.

41. Alignment of Blast-holes in Pre-splitting

42. Generation of Discontinuity in Pre-splitting • Pre-splitting holes stemmed very lightly. • Used mostly in road cuts and foundation blasts where structural concrete is directly poured against the rock wall.

43. Explosives • An Explosive is a solid or liquid substance or mixture of substances which change themselves instantaneously into a large volume of gases of high temperature or pressure when a flame, heat or sudden shock is applied to it. • The amount of energy developed per unit of time is of the magnitude of 25000 MW - i.e it exceeds the power of most of world’s present largest power station

44. Explosives • 13th century Gunpowder used in military purposes • 17th century gunpowder used in mines for blasting • 19th century French Scientist Sobrero prepared NG explosives • Alfred Noble used it in 1st commercial high explosives, dynamite

45. Classes of Explosives • Low Explosives • High Explosives • Low Explosives Example Gun powder • High Explosives Example Nitroglycerine Dynamite

46. Types of Explosives • Nitro compound explosives • Nitrate mixture explosives • LOX explosives • SMS explosives • ANFO explosives

47. Safety Code For Blasting And Related Drilling Operations Container (for quantity up to 5 kg). • Designed insulated container with lid. • Wood - 50 MM thick. • Plastic - 6 MM thick. • No metal parts. • Carrying device –. • Rubber, leather, canvas. • Separate container for Explosives / detonator.

48. Safety Code For Blasting And Related Drilling Operations Should be clearly marked for: • Mfg name or trade name. • Name of the explosive. • Lot number. • Date of mfg. / Expiry date. EXPLOSIVES – HANDLE WITH CARE

49. Safety Code For Blasting And Related Drilling Operations • Vehicle. • Licensed driver. • “EXPLOSIVES” lettering on both sides of vehicle and end. • Fitness of all parts. • Explosives & detonators – separate vehicle. • Material to be carried to site in original container. • CO2fire extinguisher kept / driver trained.

50. Safety Code For Blasting And Related Drilling Operations STORAGE OF EXPLOSIVE (magazine). • Explosives & blasting caps - separate storing. • 8 M all sides - free from vegetation, debris and combustible. • Desensitizing agent used, in case of leakage of nitroglycerine. • Lightning protection in accordance with IS : 2309 & tested once a year.