Excavation Safety Glossary
- Accepted engineering practices:
- those requirements which are compatible with standards of practice required by a registered professional engineer.
- Actual slope
- the slope to which an excavation face is excavated
- Aluminum Hydraulic Shoring:
- a pre-engineered shoring system comprised of aluminum hydraulic cylinders (cross braces) used in conjunction with vertical rails (uprights) or horizontal rails (wales). Such system is designed specifically to support the sidewalls of an excavation and prevent cave-ins.
- Bell-bottom pier hole:
- a type of shaft or footing excavation, the bottom of which is made larger than the cross section above to form a belled shape.
- Benching (Benching system):
- a method of protecting employees from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels or steps, usually with vertical or near-vertical surfaces between levels.
- Cave-in:
- the separation of a mass of soil or rock material from the side of an excavation, or the loss of soil from under a trench shield or support system, and its sudden movement into the excavation, either by falling or sliding, in sufficient quantity so that it could entrap, bury, or otherwise injure and immobilize a person.
- Close Sheeting:
- the placement of planks side-by-side allowing as little space as possible between them.
- Competent person:
- one who is capable of identifying existing and predictable hazards in the surroundings, or working conditions which are unsanitary, hazardous, or dangerous to employees, and who has authorization to take prompt corrective measures to eliminate them.
- Cross braces:
- mean the horizontal members of a shoring system installed perpendicular to the sides of the excavation, the ends of which bear against either uprights or wales.
- Distress:
- a cave-in is imminent or is likely to occur. Distress is evidenced by such phenomena as the development of fissures in the face of or adjacent to an open excavation; the slumping of material from the face or the bulging or heaving of material from the bottom of an excavation; the spalling of material from the face of an excavation; and raveling, i.e. small amounts of material such as pebbles or little clumps of material suddenly separating from the face and trickling or rolling down into an excavation.
- Excavation:
- any man-made cut, cavity, trench, or depression in an earth surface, formed by earth removal.
- Faces or sides:
- the vertical or inclined earth surfaces formed as a result of excavation work.
- Failure:
- the breakage, displacement, or permanent deformation of a structural member or connection so as to reduce its structural integrity and its supportive capabilities.
- Hazardous atmosphere:
- an atmosphere which by reason of being explosive, flammable, poisonous, corrosive, oxidizing, irritating, oxygen deficient, toxic, or otherwise harmful, may cause death, illness, or injury.
- High concentration of a flammable gas:
- a concentration in excess of 20 percent of the lower flammable limit of the gas.
- Kickout:
- the accidental release or failure of a cross brace.
- Maximum allowable slope:
- the steepest incline of an excavation face that is acceptable for the most favorable site conditions as protected against cave-ins, and is expressed as the ratio of horizontal distance to vertical rise (H : V)
- Mudsills:
- wales installed at the toe of the trench side. wales embedded into the mud that support the uprights from kicking out.
- Occupational illness:
- any abnormal condition or disorder caused by exposure to environmental factors associated with employment. For excavations this might include illnesses caused by the inhalation of toxic vapors
- Occupational injury:
- any injury such as a cut, fracture, sprain or amputation that results from a work related accident or from exposure involving a single incident at work
- Oxygen Deficiency:
- Oxygen deficiency occurs in atmospheres containing less than 19.5 percent oxygen.
- Protective system:
- a method of protecting employees from cave-ins, from material that could fall or roll from an excavation face or into an excavation, or from the collapse of adjacent structures. Protective systems include support systems, sloping and benching systems, shield systems, and other systems that provide the necessary protection.
- Ramp:
- an inclined walking or working surface that is used to gain access to one point from another, and is constructed from earth or from structural materials such as steel or wood. (see structural ramp)
- Registered Professional Engineer:
- a person who is registered as a professional engineer in the state where the work is to be performed. However, a professional engineer, registered in any state is deemed to be a "registered professional engineer" within the meaning of this standard when approving designs for "manufactured protective systems" or "tabulated data" to be used in interstate commerce.
- Sheeting:
- the members of a shoring system that retain the earth in position and in turn are supported by other members of the shoring system.
- Shield(Shield system):
- a structure that is able to withstand the forces imposed on it by a cave-in and thereby protect employees within the structure. Shields can be permanent structures or can be designed to be portable and moved along as work progresses. Additionally, shields can be either pre-manufactured or job-built in accordance with 1926.652(c)(3) or (c)(4). Shields used in trenches are usually referred to as "trench boxes" or "trench shields."
- Shoring (Shoring system):
- a structure such as a metal hydraulic, mechanical or timber shoring system that supports the sides of an excavation and which is designed to prevent cave-ins.
- Short-term exposure:
- a period of time less than or equal to 24 hours that an excavation is open. This applies only to excavations in Type A soil less than 12 feet deep.
- Sides:
- See "Faces."
- Skip or spot shoring:
- when individual timber uprights or individual hydraulic shores are not placed in contact with the adjacent member.
- Sloping (Sloping system):
- a method of protecting employees from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation so as to prevent cave-ins. The angle of incline required to prevent a cave-in varies with differences in such factors as the soil type, environmental conditions of exposure, and application of surcharge loads.
- Stable rock:
- natural solid mineral material that can be excavated with vertical sides and will remain intact while exposed. Unstable rock is considered to be stable when the rock material on the side or sides of the excavation is secured against caving-in or movement by rock bolts or by another protective system that has been designed by a registered professional engineer.
- Structural ramp:
- a ramp built of steel or wood, usually used for vehicle access. Ramps made of soil or rock are not considered structural ramps.
- Support system:
- a structure such as underpinning, bracing, or shoring, which provides support to an adjacent structure, underground installation, or the sides of an excavation.
- Tabulated data:
- tables and charts approved by a registered professional engineer and used to design and construct a protective system.
- Tight sheeting:
- the use of specially edged timber planks, like tongue and groove at least 3 inches thick. Steel sheet piling or similar construction that resists the lateral pressure of water and prevents loss of backfill is also tight sheeting.
- Trench (Trench excavation):
- a narrow excavation (in relation to its length) made below the surface of the ground. In general, the depth is greater than the width, but the width of a trench (measured at the bottom) is not greater than 15 feet (4.6 m). If forms or other structures are installed or constructed in an excavation so as to reduce the dimension measured from the forms or structure to the side of the excavation to 15 feet (4.6m) or less (measured at the bottom of the excavation), the excavation is also considered to be a trench.
- Trench box:
- See "Shield."
- Trench shield:
- See "Shield."
- Uprights:
- the vertical members of a trench shoring system placed in contact with the earth and usually positioned so that individual members do not contact each other. Uprights placed so that individual members are closely spaced, in contact with or interconnected to each other, are often called "sheeting."
- Wales:
- horizontal members of a shoring system placed parallel to the excavation face whose sides bear against the vertical members of the shoring system or earth.
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This page was last updated on
Monday, September 17, 2007
