IMT 120

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IMT 120

• Chapter 11
• Site Preparation

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The man in this photo could be digging his own
grave.  His yellow hardhat is a pathetically
inadequate safety device, given the extreme
danger that surrounds him.  He is alone at the
bottom of an 22 ft. deep vertical
trench.   Excavated soil has been stockpiled at
the very edge of the trench, adding to the
pressure on the trench walls.  Vibrations from a
backhoe operating at the perimeter of the
excavation increases the likelihood of a
cave-in.  Neither a ramp nor ladder has been
provided for the worker to escape.  Finally there
is nothing to protect him from a cave-in no
sloping back of the trench walls, no shoring of
the walls, and no shielding of the worker.
Unfortunately, this is an all too common site in
excavation work.  
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Engineering Responsibilities

• Installation plans Which include
• Foundations, footers
• Drawings
• Core samples
• Following manufacturers requirements

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Maintenance Responsibilities

• The plans from engineering detail
• What, when, how, where
• Rental equipment needed available
• The 7 P's

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Relocation of Utilities

• Plot plans should show underground lines
• Always assume that these lines are live or
  charged
• Keep inconvenience to a minimum
• Jumpers may be used to maintain utilities to
  maintain production
• Hazardous gases or chemical lines require special
  handling

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Relocation 2

• Unhook both ends of electric cables.
• Why ???
• Use test equipment to check for hot wires.
• Use blank ends, caps or plugs on piping.
• Remember!!!! The plot plan may not be 100
  accurate.

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Excavation Relocation

• Be careful where you dig!!!
• You will be the first to know if something goes
  wrong!

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Protect Exposures

• Digging close to other walls may weaken them
  Shore them with braces
• Cover equipment to keep dirt/dust off
• Protect air intakes, oil tank breathers
• Erect temporary walls where needed

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Barricades

• Protect the worksite and anybody foolish enough
  to get too close
• Prevent liability?

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Excavation of Material

• Clear area of trash
• Pile reusable material away from the work area
  but close enough to use for back filling

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This worker is in a trench with no protective
system, that is not sloped or benched and has no
means of egress.
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These workers are not protected from a cave-in,
nor do they have any apparent safe access or
egress from the trench.
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• How Do I Avoid Hazards?
• Provide stairways, ladders, ramps, or other safe
  means of egress in all trenches that are 4 feet
  deep or more.
• Position means of egress within 25 lateral feet
  of workers.

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• Test for low oxygen, hazardous fumes and toxic
  gases, especially when gasoline engine-driven
  equipment is running, or the dirt has been
  contaminated by leaking lines or storage tanks.
  Insure adequate ventilation or respiratory
  protection if necessary.
• Provide safe access into and out of the
  excavation.
• Provide appropriate protections if water
  accumulation is a problem.

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• Inspect the site daily at the start of each
  shift, following a rainstorm, or after any other
  hazard-increasing event.
• Keep excavations open the minimum amount of time
  needed to complete operations.

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Foundations

• Generally, a table-like slab of concrete, partly
  above grade, on which equipment will rest
• May be very heavy may have expansion joints
• May have rebar or other reinforcement devices

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Poured Foundation
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Footers

• Support the foundation
• Sit on hard packed ground
• Hard rock supports the most weight
• Soft clay loose sand supports the least weight
• The size of the footing depends on the weight of
  the load the soil conditions

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Reinforced Concrete

• Steel bar or wire mesh help prevent cracks due to
  expansion/contraction caused by temperature
  changes.
• Use de-formed bars, not smooth bars.
• Reinforcing material increases the tensile
  strength of concrete.
• Generally, wire is used for flat areas.

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Concrete Forms

• Wood forms are cheapest but dont last long
• Metal forms are expensive but last a long time
• Plastic liners can be used where the concrete
  surface will show (the liners make a better
  finish)
• Brace support the forms
• Why???

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Concrete

• Ready-mixed is easy good for most jobs
• Order as needed
• Aggregates make the concrete stronger
• Sand, gravel, fiberglass
• Must be clean
• For mixing by hand, use 5 1/2 bags of cement per
  cubic yard of concrete needed

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Concrete 2

• Protect uncured concrete from freezing
  temperatures
• Cover with film, burlap, canvas, tarpaper
• Use hot air blowers or heaters
• Never use salt
• Back fill as needed

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Anchor Bolts

• Generally, installed before pouring the concrete
  or before the concrete sets up
• Use a template for accuracy
• Light metal or wood
• Protect threads with tape, tubes, or grease
• Why ???
• Different shapes available J, T, L or tube type

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Alignment Plates

• Allow easy adjustment to the machine or equipment
  being installed
• May be included with a new machine or it may be
  made by maintenance
• May require to be set in the freshly poured
  concrete

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Concrete Finishing

• Most foundations do not require a pretty finish
• For areas that will be in contact with water,
  oil, or chemicals-a finished surface is needed,
  use an epoxy based concrete sealer
• Smooth concrete wears better is more durable

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Concrete Finishing 2

• Non-slip surfaces can be done by adding
  carborundum grit to the surface just after
  finishing
• Finishing must be done before the concrete begins
  to set up (about 45 minutes)
• Screed, screed, float, float, trowel
• Vibrators, power floats, special trowels, driving
  poles

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Concrete Finishing 3

• Keep damp for 7 days, a slow cure means a
  stronger concrete
• Do not install equipment for 28 days
• (This does not reflect reality but the ideal
  situation)

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Odds Ends

• Watch for tripping hazards between different
  floor levels
• Build ramps or put in fill
• Do permanent surfaces ASAP

• PPE-safety glasses, goggles, rubber gloves
  footwear, hard hat
• Cave in protection
• Plywood, jacks, timbers, planks or commercial
  trenching protection

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The End !!!!!!