What Does Trench Shoring Mean?
Trench shoring is the practice of adding support to the side walls of an excavated trench in order to prevent soil cave-in or collapse. Shoring materials include steel, aluminum, or wood panels supported by screws or hydraulic jacks.
Trench shoring is also known as trench bracing and trench lining.
Safeopedia Explains Trench Shoring
An excavation is considered a trench if its depth is greater than its width, and is no more than 15 feet wide.
Shoring trenches protects the workers who work in them. The shoring materials are removed once the work is complete or the trench is to be filled.
Types of Trench Shoring
There are various approaches to trench shoring, including the following shoring methods.
Hydraulic shoring is the most popular shoring method and uses prefabricated struts and aluminum or steel wall systems. These systems pump hydraulic pistons outward until they press tightly against the trench walls.
Hydraulic shoring is safe, since these shoring systems can be installed or removed without requiring workers to enter the trench. It is also light, quick to install, and can accommodate different trench sizes.
Pneumatic shoring is similar to hydraulic shoring, except that it uses air pressure from an air compressor to install the shoring system.
Soldier Pile and Lagging
Soldier piles are vertical piles inserted in the trench at regular intervals with timber lagging positioned between them as the excavation proceeds. This system is used only for temporary construction and is difficult to use where there is a high water table.
Soil Nails and Shotcrete
Soil nails are closely spaced steel bars that are driven into the soil, with head plates installed on each bar. Shotcrete or concrete is then applied on the wall face to provide continuity.
OSHA Requirements for Trench Shoring
Where trenches are dug, employers are required to comply with OSHA's 29 CFR 1926.651 and 1926.652 standards, or similar state plan requirements approved by OSHA.
The shoring requirements will depend partly on the depth of the trench:
- For trenches less than 5 feet deep, a competent person will determine whether a protective system is required
- For trenches between 5 and 20 feet deep, a protective system must be put in place unless the trench is made entirely of stable rock
- For trenches deeper than 20 feet, the protective system must be professionally designed in accordance with 1926.652 (b) (c)
Employers must also ensure that the trenches are inspected daily. When conditions change, these inspections must be conducted by a competent person in order to determine whether any new hazardous conditions are present.