- Project plans
- Project activities
- Legislation and standards
- Industry context
- Specialist wikis
Last edited 05 Nov 2021
Types of excavation
On small sites or in confined spaces, excavation may be carried out by manual means using tools such as picks, shovels and wheelbarrows. Larger scale excavation works will require heavy plant such as bulldozers and backactors. For more information, see Excavating plant.
This involves the removal of the exposed layer of the earth’s surface, including any vegetation or decaying matter which could make the soil compressible and therefore unsuitable for bearing structural loads. The depth will vary from site to site, but is usually in a range of 150-300 mm.
 Muck excavation
 Unclassified excavation
 Excavation purpose
This is the process of excavation whereby the material that is cut or stripped. The removed topsoil and earth can be used as fill for embankments, elevated sections, and so on. It can also be used to form a level surface on which to build, as elevated sections of the site are ‘cut’ and moved to ‘fill’ lower sections of the site.
Trench, or footing, excavation is typically used to form strip foundations, buried services, and so on. The choice of technique and plant for excavating, supporting and backfilling the trench depends on factors such as; the purpose of the trench, the ground conditions, the trench location, the number of obstructions, and so on.
The common techniques that are used include:
- Full depth, full length: Suitable for long narrow trenches of shallow depth, such as pipelines and sewers.
- Full depth, successive stages: Suitable for deep trenches where works can progress in sequence, reducing the risk of collapse.
- Stage depth, successive stages: Suitable for very deep trenches in confined areas, deep foundations and underpinning.
This typically involves the removal of material for the footing and abutments of bridges. The work may be subdivided into wet, dry and rock excavation. Underwater excavations may require special methods of drill and blast. For more information, see Bridge construction.
 Excavation support
Materials have different stability characteristics during excavation works. The ‘angle of repose’ of the material describes the steepest angle at which it will remain stable without support. The exact angle of repose will depend on the presence of groundwater, but some typical angles are:
- Drained clay: 45-degrees.
- Wet clay: 16-degrees.
- Gravel and dry sand: 40-degrees.
- Wet sand: 22-degrees.
- The stability and angle of repose of the subsoil.
- The proximity of the excavation to vehicles, services and buildings.
- The level of the water table.
- The type/s of subsoil.
- The depth of the excavation.
- The length of time the excavation will be left open.
- The time of year and weather conditions.
The types of support that can be used include:
- Timber supports: Commonly used for low risk, narrow trenches, shafts or headings.
- Trench boxes: Can be placed in pre-excavated trenches in low-risk situations.
- Trench sheets: Can be overlapping or interlocking, and are used to provide continuous support for deeper trenches.
- Ground anchors and rock bolting.
- Basement excavation.
- Building foundations.
- Excavating plant.
- Ground improvement techniques.
- Mass haul movement.
- Over excavation.
- Pile wall.
- Raising awareness of dewatering regulation.
- Road construction.
- Surplus excavated material.
- Temporary works.
- Trench support.
- Trial pit.
- Types of soil.
Featured articles and news
A national valuation to fund old-age pensions.
The world’s largest Commonwealth memorial to the missing.
Long after the end of the defects liability period.
Occupant satisfaction and wellbeing in buildings.
From the simple to the complex.
And the UK Government guidelines.
Commitment agreed to by major built environment bodies.
Electrical skills, low carbon, high-tech and the building services revolution.
Ultra-deep drilling with millimeter-wave beam technology.
Looking at the built environment from space.
BSI standards 8671, 8672 and 8673.
Bringing life to burial grounds.
From failed modernism to twenty-minute neighbourhoods.
The gates process and change control.
Why people behave as they do. APM book.