Topic 16: Excavations and Trending

Type C Soil: Type C soil it is a ...

Gravel, wet loamy soil, sand, and submerged soil. 1 to 1-½ ratio

Sloping

a technique that employs a specific angle of incline on the sides of the excavation. The angle varies based on assessment of impacting site factors.

Bracing

all froms of slope support must be braced against soil and water pressures

. Two or more ladders must be used where 25 or more workers are working in an excavation in which ladders serve as ...

as the primary means of entry and exit or where ladders are used for two-way traffic in and out of the trench

All shoring systems require some sort of ....

bracing

Cave-in Conditions: Vibrations from ....

construction equipment, nearby traffic, or trains (Liquefaction)

Trenching hazard: Electrical shock from striking ...

electrical cable in the trench or striking overhead lines.

The type of protection that would be specified under soft soil conditions in deep excavations (deeper than 20-feet), and in excavations near building foundations must be an ....

engineered vertical shoring system (like slurry walls with tie-backs).

Rakers

external diagonal bracing

Crosslot Bracing

external framework of bracing

When water is present in an excavation it is ....

extremely hazardous to enter

Cave-ins are the ----

greatest risk!

tieback

internal braces

dewatering

pump water from pits (sumps) in the excavation

Soil Mixing can be used to:

remediate contaminated soil • cut off underground flow of water • stabilize and strengthen areas of weak soil

Sloped or benched excavation is less expensive than ------, but requires a site without nearby property lines, adjacent structures, or other limits on excavation.

sheeted excavation

Sloping employs a specific angle of incline on the .....

sides of the excavation.

OSHA requires that a qualified person determines ....

the soil quality and the sloping/shoring requirements

Slurry walls

use a "clam shell" bucket to excavate - use pumps for the slurry and the concrete

Higher volumes of water: use..

well points and/or barrier wall

Competent Person Must have had specific training in and be knowledgeable about:

• Soils classification • The use of protective systems • The requirements of the standard

soil mixing

A technique of adding a modifying substance to soil (like portland cement) and blending it by means of augers or paddles rotating on the end of a vertical shaft

Soldier Beams and Lagging

(vertical H-pile steel columns w/ horizontal heavy wood planks in between) is a special type of sheet piling)

Sheet Piling

(vertical planks of wood, steel, or precast concrete driven tightly against one another)

Trench

- a narrow excavation. The depth is greater than the width, but not wider than 15 feet. So a trench is a special type of excavation.

Shield

- a structure able to withstand a cavein and protect employees (trench box)

Trench Shield/Trench Box

A structure able to withstand a cave-in and protect employees Also called

Be sure that the vertical walls of a trench box extend at least --" above the lowest point where the excavation walls begin to slope.

18

The top of the trench shield must extend at least -----above the excavation!

18-inches

Keep lumber, tools, spoils at least----from the edge in order to keep them from falling into the excavation.

2-feet

There must be a minimum of --- between the edge of the excavation any equipment, tools, or spoils.

2-feet

Sloping the sides of an excavation no less 1.5:1 ratio (horizontal:vertical) helps to ensure worker safety in excavations up to ---ft deep (Even in type -- soil)

20

An exit from the trench box and the excavation must be located within --' of each worker

25

Ladders and ramps used as exits must be located within --' of every person in a trench that is over -' deep

25/4'

Benching steps can be no more than ---- in height each

4-feet

Shoring or sloping is required for excavations deeper then ___ ft.

5

Make sure shoring, trench boxes, benching, or sloping are used for excavations and trenches over -- deep

5'

Most accidents occur in trenches ---feet deep

5-15

Subparts P: Excavations 1926..---/ Scope, Application, and Definitions

650

1926.--- / Specific Excavation Requirements

651

1926.---/ Requirements for protective systems

652

Hydraulic Shores:

Can be installed and removed quickly and safely

Type B Soil: Type B soil it is a 1 to 1 ratio

Crushed rock, silt, sandy loam, unstable rock/ 1 to 1 ratio

Type A Soil: The minimum slope (expressed as a rise to run ratio) for an excavation or trench with Type A soil is a...

Dry clay, silty clay, sandy clay, and clay loam. 1 to ¾ ratio

Other hazards include: ➢ Asphyxiation due to lack of oxygen ➢ Inhalation of toxic materials ➢ Fire ➢ --------k ** ➢ Moving machinery near the edge of the excavation can cause a collapse ➢ Accidental severing of underground utility lines

Electric Shock

Interlocking Steel Sheeting:

May be specified under certain conditions such as deep excavations near building foundations

Vertical Sheeting

May be used for long-term excavations and supported with hydraulic wales

Shoring

a structure that supports the sides of an excavation and protects against cavei ns (built in-place structure)

Always assume worst-case: ----- soil conditions, unless a qualified person has determined otherwise.

Type "C"

Benching is NOT allowed in --- soil Benching allowed only in cohesive soils (---- and above)

Type "C"/Type "B"

Excavation

a man-made cut, cavity, trench, or depression 18-inches deep or more formed by earth removal.