Trench Shoring Basics
Definitions from the Excavation Standard Sub-Part P 1926.650 (b)
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 (walers). This system is designed to support the sidewalls of an excavation and prevent cave-ins.
Benching — a method of protecting workers from cave-ins by excavating the sides of an excavation to form one or a series of horizontal levels. This method of protection may only be used in cohesive soils.
Cave-in — the separation of a mass of soil or rock from the side of an excavation, or the loss of soil from under a trench shield or support system and its sudden movement into an excavation.
Competent Person — one who is capable of identifying existing and potential hazards in the surroundings or working conditions that are unsanitary, hazardous, or dangerous to workers and who has the authorization to take prompt corrective measures to eliminate them.
Excavation — any man-made cut, cavity, trench or depression in the earth’s surface.
Failure — the breakage, displacement or permanent deformation of a structural member or connection point, as to reduce its structural integrity and supportive capabilities.
Kick-out — the accidental release or failure of a cross brace.
Protective System — a method of protecting workers 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, shield systems, benching systems and other systems that provide the necessary protection.
Ramp (or Ramping) — an inclined walking or working surface that is used to gain access to one point from another.
Shield (or Shield System, generally referred to as a Trench Box) — a structure that is able to withstand the forces imposed on it by a cave-in and thereby protects workers 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 Federal Requirements 1926.652 (Federal Requirements for Protective System under 29 CFR Part 1925).
Shoring (or Shoring System) — a structure such as a hydraulic or timber shoring system that supports the sides of an excavation and is designed to prevent cave-ins.
Sloping (or Sloping System) — a method of protecting workers from cave-ins by excavating to form sides of an excavation that are inclined away from the excavation. 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.
Support System — a structure such as underpinning, bracing or shoring that provides support to an adjacent structure or the sides of an excavation.
Tabulated Data — tables and charts approved by a registered professional engineer, which are used to design and construct a protective system.
Trench — 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.
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.
Aluminum Shoring Products
Aluminum shoring products provide lightweight solutions that are compatible with the limited lifting capacities of today’s smaller excavators. Hydraulic trench shields with end panels, hydraulic vertical shores with extensions and fin form, Lite-Shields and 4" wall aluminum trench boxes are available.
Steel Shoring Products
Our steel trench shields (trench boxes) rental fleet provides contractors the maximum in flexibility and protection while performing both deep and shallow cuts. Our standardized fleet makes stacking applications, three or four sided pits and adding height adaptors for increased pipe clearance simple and consistent.
Manhole Shields and Bedding/Rock Boxes
Designed to provide a safer workplace and to boost efficiency. Manhole shields assemble in minutes in the field, are stackable and are available in multiple sizes for various applications. Bedding/rock boxes reduce the spillage of materials on the job site, reducing material costs.
Rules of Thumb
1. Any job site where an excavation or trench is created that job-site is required by OSHA to have a Competent Person on-site.
2. Any excavation 5 feet or less with a potential for a cave-in requires the use a shoring or shielding system. Many die needlessly each year in shallow excavations. It is the Competent Persons responsibility to prevent any exposer to cave-in dangers.
3. A ladder, ramp or other safe means of egress shall be located in trench excavations that are 4 feet or more in depth so as to require no more than 25 feet of lateral travel for workers.
4. No one should work in excavations with accumulated water or where water is accumulating unless adequate precautions are taken, such as a wellpoint system and shoring system.
5. Dirt spoil piles or other materials shall be located a minimum of 2 feet from the edge of an excavation.
6. No one shall be allowed in shields when they are being installed, removed or moved vertically. They may however remain in the protective system while it is being moved horizontally in the trench.
7. A shield may be up to 2 feet above the bottom of the trench, but only if the shield is rated for the full depth of the trench and there is no loss of soil from behind or below the bottom of the shield.
8. Soil that remains in clumps when excavated is cohesive. Soil that breaks easily and does not stay in clumps is granular.
9. One cubic foot of saturated soil weighs approximately 114 pounds.
10. One cubic yard of saturated soil weighs approximately 3,078 pounds or 1-1/2 tons.
Please see your Sunbelt Sales Representative for assistance in site-specific or more detailed trench shoring applications.