Page 7 - Trench and Excavation

Sheet Pile- Special made inter-locking steel sheeting commonly used in submerged or saturated
moisture conditions.
Sheeting- Members of a shoring system that retains the earth in position and in turn are supported
by other members of the shoring system.
Shield- A structure which can withstand the forces imposed upon it by a cave-in and thereby
protecting the workers within.
Shoring- A structure which is designed to prevent an excavation cave-in by applying compressive
pressure to the sides of the excavation.
Short-Term Exposure- A period of time which is less than 24 hours that an excavation is open.
Silt- Soil material which is composed of mineral fragments that range from 0.002mm to 0.05 mm
in diameter.
Sloping A method of protecting workers from cave-ins by excavating the sides of the trench at
an incline away from the trench.
Spall- Segments of soil that break off the excavation wall.
Spoil- A pile of soil which has been removed to form the trench.

Stable Rock- Natural solid mineral material that can be excavated with vertical sides and will
remain intact while exposed.

Straight Trench- A trench where the wall of the trench meets the floor at roughly right angles.
Stringers- Another name for cross-braces.
Submerged Soil- Soil which is under water or is freely seeping water.

Support System- A structure such as underpinning, bracing, or sharing which provides support
to an adjacent structure, underground installation, or the sides of the excavation.

Surcharge- The weight contributed to the walls of the trench by a load (e.g., spoil pile, heavy
equipment, pipe, etc.) adjacent to the trench.

Surface Encumbrances- items on the soil at the top of the trench which, if not immobilized, could
fall into the trench.
Tabulated Data- Charts and tables approved by a Registered Professional Engineer and used to
design and construct a protective system.
Tensions Cracks- cracks in the earth parallel to the trench, which indicate subsistence of the
trench wall and may foretell of a cave-in. Also known as Stress Cracks.
Thumb Penetration Test- A method of determining the soil type by judging how difficult it is to
indent a soil sample with a thumb.
Tight Sheeting- Plank sheeting with inter-locking edges which is used as a watertight barrier for
submerged or saturated soil conditions. Steel sheet pile is also tight sheeting.
Timber Shoring- Trench support system made from wooden timbers.
Toe- leading edge of a slope of soil

TRENCH- A narrow excavation made below the surface of the ground which is generally deeper
than it is wide, but whose overall width at the bottom is less than 15 feet.

Trench Shield- A mobile trench shield.

Trench & Excavation
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