- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 08 Jan 2019
Help develop this article - click 'Edit this article' above
A trench is defined as an excavation when its length greatly exceeds its depth. Shallow trenches are usually considered to be less than 6 m deep and deep trenches greater than 6 m. Depending on the dimensions of a trench, excavation can either be carried out by hand or using a mechanical digger. Trenches are commonly required to allow services, pipelines or foundations to be laid.
Over short periods of time for relatively shallow depths most soil types will stand almost vertically without any problems. However, trenches other than those which are relatively shallow may require a trench support scheme.
Historically, trenching involved using timber to support horizontal and vertical soil loads and this technique is still used today. Timber trenching is generally used for low risk, narrow trenches, shafts or headings. The timber solutions require good workmanship and are reasonably labour-intensive, however they are versatile and the equipment required is easy to handle and transport.
Trench boxes are suitable for low-risk situations in stable, dry ground and can be placed in pre-excavated trenches or installed using the ‘dig and push’ technique. The system requires at least two struts at each panel for stability which must be considered when access is required for construction work or piping.
For more information, see Trench box.
Trench sheets are the most adaptable of the systems available, and are most commonly used to retain poorer soil. They can support deeper trenches with larger surcharges and provide a continuous support. They require multiple levels of strut support and the slenderness of the sheets can often limit the depth of the trench as they are installed by light machinery and could buckle under large vertical loads.
 Related articles on Designing Buildings Wiki
- Crane supports.
- Facade retention.
- Health and Safety.
- Temporary works.
- Trench box.
- Trenching equipment.
 External references
Featured articles and news
Evaluating occupant satisfaction.
The Ancona eco-mansion
What is the cost of not getting it right first time?
The government announces a new role as part of a wider package of safety reform.
Lessons for the next UK road investment strategy.
Architectural Technology Studio 3
Construction Industry Advisory Committee CONIAC
The real impact of late payment.
How to tell which infrastructure projects will work.
The government announces the biggest change in building safety for a generation.
Key messages from the UN COP 25 conference.