- Project plans
- Project activities
- Legislation and standards
- Industry context
Last edited 13 Apr 2018
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
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.
- Deleterious materials.
- Design liability.
- Facade retention.
- Health and Safety.
- Temporary works.
- Trench box.
- Trenching equipment.
 External references
- BS5975:2008 + A1: 2001 Code of Practice for Temporary Works Procedures and the Permissible Stress Design of Falsework (BSI 2011).
Featured articles and news
Dr Nicholas Falk, director of the URBED Trust, explains why metro cities are the future of urbanisation.
From next week, UK firms can bid for a share of a £12.5m fund to boost productivity, performance and quality.
A right to light generally refers to the right to receive sufficient light through an opening.
Interference and compatibility - the effects of electromagnetic fields in the workplace.
Important action is being taken to inspire young people to train as engineers.
A survey of Leicester’s historic buildings resulted in local listing being taken more seriously.
Demolition is the most high risk activity in the construction sector. Read our introductory article here.
BSRIA report on the domestic boiler market, with China recording the most 'dynamic market uptake'.
Do we really know everything important about the impacts of our infrastructure projects? And if we don’t, does it matter?
Former Chief executive Richard Howson blames government for being 'poor payers'.