Is shoring and other trenching safety methods required during trenchless construction?
While the term "trenchless" suggests the absence of trenches, there are instances where small excavations are needed during trenchless construction. These trenches, known as entry and exit pits, are openings located at the beginning and endpoints of construction operations.
They are necessary to make room for equipment and personnel during drilling and boring activities. (Read An Unboring Yet Basic Guide to Boring.)
Pipe jacking, pipe ramming, horizontal directional drilling (HDD), and microtunneling are just some of the trenchless construction methods that require the excavation of entry and exit pits. (Read Planning a Microtunneling Project: What You Need to Know Before You Begin.)
Compared to conventional open-cut excavating methods, these pits are considerably smaller and less intrusive. However, they can still be significant enough to be a safety concern for on-site personnel. Entry and exit pits are typically rectangular-shaped cuts with vertical or near-vertical walls.
They are also done in soils with varying strength and stability properties. Therefore, temporary protective structures are needed to retain the soil at the walls of the pits to prevent collapse, especially in unstable soil conditions.
According to the Occupational Safety and Health Administration (OSHA), protective measures, such as shoring, are required in all excavated trenches equal to or greater than five feet (1.5m) in depth unless the excavation is done entirely in stable rock (rarely the case for trenchless construction).
For trenches exceeding 20 ft. (6.1m), protective measures need to be designed and approved by a registered professional engineer.
Some of the most common types of shoring methods used in trenchless construction include:
- Soil nail shoring.
- Soil anchoring.
- Sheet pile shoring.
- Soldier piles and lagging.
- Secant or tangent piles.
In addition to providing protective shoring, construction companies should also take other precautionary measures to protect workers in entry and exit pits, such as:
- Providing a safe means of getting in and out of the trench.
- Placing spoils, materials, equipment, and tools a minimum distance of two feet away from the edge of the excavation.
- Controlling groundwater.
- Ensuring that work is performed by competent individuals.
- Enforcing the use of appropriate personal protective equipment (PPE).
Written by Krystal Nanan | Civil Engineer
Krystal is a civil engineer and project manager with an MSc in Construction Engineering and Management. Her experience includes the project management of major infrastructure projects, construction supervision, and the design of various infrastructure elements including roadway, pavement, traffic safety elements and drainage.
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