Safety in Excavation & Demolition

1. 84 HOURS SAFETY & HEALTH TRAINING MODULE
PATNA METRO RAIL PROJECT SITE
PNM ENVIRO-SAFE SOLUTIONS PVT. LIMITED
EXCAVATIONS & DEMOLITON

2. Excavation Definition

3. Trenching
A narrow excavation (in relation to its
length). In general the depth is greater
than the width, but the width of a
trench (measured at its bottom) is not
greater than 15 feet.
Bulk Excavation
An excavation whose width is greater
than 15 feet.

4. Excavation Hazards
1. Cave – ins
2. Overhead Electric Line Contact
3. Falls into Excavations
4. Equipment Falling into
Excavations
5. Explosion / Fire / Electrocution

5. Tragic facts

6. Tragic facts
 Excavating is recognized as one of the most
hazardous construction operations
 541 Workers were killed on Excavation/Trenching
jobs from1992-2001
 411 (76%) were killed by cave-ins
 257 (47%) worked for companies employing less
than 10 people
 Cave-ins can happen without warning
 All of the fatalities and injuries could have been
prevented

7. Cause :Unsafe Act
 Attitude
 “I Know what I’m doing.”
 “It can’t happen to me.”
 “I’ve been doing it that way for years.”
 “I’d sleep in that hole!”
 “Don’t worry, we’ll watch the walls and tell you if you need to get out.”
 Management Factors
 Poor Planning
 Lack of knowledge on safety procedures
 Misjudgment of soil type.
 Inadequate, or incorrect installation of protective devices.
 Defective protective devices.
 Failure to adjust for changing conditions

8. Understand Cave in

9. Understand Cave in

10. Understand Cave in
Effects :
Respiratory distress
Crush syndrome
Total body impact

11. Soil classification

12. Stable Rock
 Natural solid mineral matter that can be excavated with vertical sides and
remain intact while exposed.

13. Soil A/B/C
Unconfined Compressive
Strength
C B A
.5 1.5
T.S.F.

14. Type A Soil
 Cohesive soil with an unconfined compressive strength of 1.5 ton per square
foot (TSF) (144kPa) or greater.
 Examples are
• Clay
• Silty Clay
• Sandy Clay
• Clay Loam
Cohesion
Friction Liquid Bonding
Cementation Chemical Bonding

15. Type A Soil
 However no soil is type A if it is
1. The soil is fissured.
2. The soil is subject to vibration from heavy traffic, pile driving, or similar
effects.
3. The soil has been previously disturbed.

16. Type B Soil
 Cohesive soil with an unconfined compressive strength greater than .5 TSF,
but less than 1.5 TSF.
 silt, silt loam,
 sandy loam,

17. Type B Soil
 Previously disturbed soils except those that would be classified as Type C
soil.
 Soil that meets the unconfined compressive strength or cementation
requirements of Type A, but is fissured or subject to vibration.
 Dry rock that is not stable.
 Material that is part of a sloped, layered system where the layers dip into the
excavation on a slope less steep than four horizontal to one vertical (4H:1V),
but only if the material would otherwise be classified as Type B.

18. Type C Soil
 Cohesive soil with an unconfined compressive strength of .5 TSF (48kPa) or
less.
 gravel, sand, loamy sand, submerged soil, soil from which water is freely seeping
 Granular soils including gravel, sand, and loamy sand.
 Submerged soil or soil from which water is freely seeping.
 Submerged rock that is not stable.
 Material in a sloped, layered system where the layers dip into the excavation
on a slope of four horizontal to one vertical (4H:1V) or steeper.

20. Shielding
Shoring
Protective Systems
Sloping

21. Sloping & Benching

22. Sloping options
1. Sloping sides 1½ h to 1 v (340) - - as though it were Type C soil.
2. Use Appendix A to classify the soil and Appendix B to determine the correct
slope. OR
 Have a registered professional engineer provide:
 Tabulated data for sloping or
 A site-specific sloping profile.

23. Sloping options
0 = 45
0 = 45
0 = 45
Type B

24. Sloping options

25. Sloping options
Wrong
Right
0 = 90
0 = 34
Benching is not allowed in Type C Soil.

27. Shoring options
 Use the timber or aluminum hydraulic shoring charts
from the OSHA Standard
- - or - -
 Have a registered professional engineer provide:
• Tabulated data
• Manufacturer’s tabulated data
• Site-specific design
Timber shoring Aluminum hydraulic shoring

29. Aluminum hydraulic shoring

30. Aluminum hydraulic shoring

31. Aluminum
hydraulic
shoring

32. Aluminum
hydraulic
shoring

38. Trenching /Excavation start
up requirements
 Land Survey for identification of
underground utilities.
 Overhead trees & electric lines.
 Identify type of soil & protective system
required.
 Notification to authorities 30 days prior
to excavation.
 Appointment of Project Engineer.
| Assume overall responsibility |
 Appointment of Responsible Person.
| Supervision | Inspection| Remedial
measures

39. Trenching /Excavation start
 Approval from authorities for underground & above
ground utilities.
 Traffic Control & illumination
 Barricading & Signage's
 Maintenance of register.
 Site rules.
|Vehicle requirements| Material stacking – 0.65 m| PPE
requirement | Excavator driver induction|
 Provision of Safe access
| Ladders | Stairs| Ramps|
 Protective system

40. Trenching - Inspection
Around Trenches
• Check ground for tension cracks around
shoring
• Check for water seepage (undermines trench
walls) around trench boxes
• Check for movement
With hydraulic shoring look for:
• Leaks in hoses and cylinders
• Bent bases
• Broken or cracked nipples
• Cracked, split or broken sheathing

41. Trenching - Inspection
With timber shoring check for:
• Cracked or bowed sheathing
• Wales crushed where they join struts
• Loose or missing cleats
• Split or bowed wales
• Struts off-level
In trench boxes look for:
• Deformed plates
• Bent or distorted welds in sleeves and struts
• Missing struts
• Bent struts
• Holes, bends or other damage to plates

42. …shall not…stay under any
material being lowered…
…Ensure driver has good field of vision

47. Excavation –Control Measures
● mum angle of slope depends on soil type category (4 soil types, based Sides of the excavation are
sloped back (battered) at an angle that is sufficiently shallow that the soil will not slip.
● Maximum angle of slope depends on soil type category (4 soil types, based on compressive strength
and texture):
• Stable rock.
• TypeA, such as clay.
• Type B, such as silt.
• TypeC, such as sand, gravel.
● compressive strength and texture):
• Stable rock.
• TypeA, such as clay.
• Type B, such as silt.
• TypeC, such as sand, gravel.

49. Excavation –Control Measures
● Sides of the excavation are sloped back (battered) at an angle that is sufficiently shallow that the soil
will not slip.Sides of the excavation are sloped back (battered) at an angle that is sufficiently shallow
that the soil will not slip.
● Maximum angle of slope depends on soil type category (4 soil types, based on compressive strength
and texture):
• Stable rock.
• TypeA, such as clay.
• Type B, such as silt.
• TypeC, such as sand, gravel.
• Type B, such as silt.
• TypeC, such as sand, gravel.

50. https://youtu.be/1EOMtamB0mw
https://www.youtube.com/watch?v=cFYkeT0Yk
6k
https://www.youtube.com/watch?v=lUgjbIK0r0
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51. DEMOLITION
 Demolition of very old, life-ended, weak or unsafe construction
becomes necessary. Sometimes it is required for a new construction,
alteration, addition or repairs on the same site. High risk is involved due
to falling or flying material, working at height or on a structure being
broken, use of heavy hand tools and heavy blows and vibration or
sudden collapse. Not only the workers but the public passing by, have
also to be protected. Proper planning, permit, procedure, sequence of
work, training of workers and safety supervision by a competent person
are some of the basic requirements.
 See Chapter XII, Rules 108 to 118 of the BOC Workers Rules, 1998, for
demolition. See Part 7 of Chapter-28 for their details.

52. Precautions Prior to Demolition :
 A definite demolition procedure should be worked after studying the
entire structure and carrying out a survey of its drawings, load bearing
members, type of foundation, walls etc., chemical contents if any, previous
use, structural problems, ground characteristics, condition of roof trusses,
type of framing used in framed structure, equipment sensitive to noise,
vibration, dust etc., radioactivity, utility or service lines, gas and power
lines, joint with or effect on adjacent building, climatic conditions etc. A
help of structural engineer is advisable.
 A method of demolition should be formulated after above survey and
recorded in a method statement after identifying the problems and their
solutions.

53. Precautions Prior to Demolition :
 All electric, gas, water and other service lines should be shut off or safely
protected against damage. The plant or building should be isolated from
all other plants or buildings.
 For protection of the public, all the roads and open areas surrounding the
work (i.e. danger or safety zone) should be fenced off (fence height at
least 2 mt) and caution boards and danger signs should be displayed in
the local language, Hindi and English at prominent places. Unauthorised
entry into it shall be effectively controlled. If a swinging weight (ball) is to
be used for demolition, width of the safety zone should be 1.5 times the
height of the structure. If a clamshell bucket is to be used for demolition,
safety zone of 8 mt from the line of travel of the bucket should be
maintained.

54. Precautions During Demolition :
 Only trained workers should be employed (new or unskilled may
cause more accidents). They should wear helmet, safety belt, safety
shoes, safety goggles and gloves.
 A part which would destroy the stability of other parts should not
be demolished. To prevent danger, parts of structure should be
adequately shored; braced or otherwise supported. Foundation
walls serving as retaining walls to support earth or adjoining
structures should not be demolished until the adjoining structure
has been underpinned or braced and the earth removed or
supported by sheet piling or sheathing.

55. Precautions During Demolition :
 Where a deliberate controlled collapse technique is to be used,
expert engineering advice should be obtained. It should be used
only where enough surrounding space is available to withdraw men
and equipment at a safe distance. Structure not carrying its design
load may be pre-weakened before a deliberate collapse, but in such
cases the pre-weakening should be carefully planned and dead
load should be reduced systematically.
 When equipment such as power shovels and bulldozers are used
for demolition, type of building, its dimensions and the power of
the equipment should be considered.

56. Precautions During Demolition :
 Where explosives are used to demolish key members, the blast protection and
safe distances should be agreed in advance. The work should be carried out by
experienced personnel in a controlled manner.
 Sometimes catch platforms (at least 1.5 mt wide) are provided along the outside
of the outer wallsto catch falling materials. The outer edge of such platform
should be higher than the inner edge (i.e. inclined to wall side) and the platform
should be lowered as the demolition work gets lowered. Sequence of
Demolition: Glass panels of doors and windows should be removed first. Then
loose objects and projecting parts including balconies should be removed. Work
should start at the top of the structure and proceed downwards. When work is
going on at upper level, workers should not be deployed at lower level. Broken
material should not be thrown but lowered safely. It should not be allowed to be
accumulated to disturb stability. Dusting should be minimised by watering. Stairs
with hand railing should be kept in place as long as practicable to provide access
and egress.

57. Precautions During Demolition :
 Scaffolds used for demolition, should be independent of the structure
being demolished. Travelling mechanical ladders can be used.
 AC sheet roofing requires careful consideration of points of support
before planning its demolition. A firm ladder resting on such point should
be given to workers to climb to the roof. Then they should use a cat
ladder or a crawling board supported on ridge to stand and remove the
sheet. In no case, they should be allowed to walk or stand directly on the
AC sheet. Underneath nearby fall arresternet should also be used.
 Walls should be demolished storey by storey and starting from the top.
Unsupported walls should be prevented from falling by shoring and, ties.

58. Precautions During Demolition :
 Floors should be demolished by using planking or walkways to stand or
move when it becomes weak to withstand the load. Openings through
which material is dropped should be fenced or barricaded.
 Tall chimneys should not be demolished by blasting or overturning unless
the sufficient open area is available for its safe fall. Workers should not
stand on chimney wall. Thrown down material should beremoved during
breaks in the work or under controlled conditions.
 Structural steelworks should be demolished by cutting its parts in such a
way that it should not collapse, twist or spring suddenly. It should be
demolished tier by tier. Cut parts should not be thrown from a height.
They should be lowered safely.

59. Precautions During Demolition :
 Industrial structure such as a nuclear power plant, hazardous
chemical or petrochemical plant or a plant containing a plenty of
asbestos material (e.g. insulation, AC sheets) should be demolished
only after consulting their respective experts or specialist engineer
and taking all precautionary measures against their specific
hazards. General rules are as stated earlier.

60. https://youtu.be/uNnvR4kxL3A

61. THANK YOU
&
SAFE WORKING DAY