Excavations of Trenches and Pits in various sub Soils
Timbering
Timbering is the method used to support the ground when excavations are done and it is inconvenient or impractical to slope the sides of the excavation back to a safe angle.
Timbers such as deal, pine, fir or the Baltic red –and whitewoods were and are still used today to provide support to the sides of an excavation. Sheet- steel piling is now frequently used, but is still classed as “timbering”. In the Standard Method of Measurement, the operation is termed “planking and strutting”
The type of timbering required depends on the factors listed in the previous section, but BS 6031:1981, ‘code of practice for earth works’ provides a guide to the general requirements
Poling Board
Board varying in length up to 2m, having a cross section of approximately 250m * 38mm, placed vertically against the face of ground
Walling Board
Horizontal timber member which supports the poling boards between struts. Size varies from 100mm * 75mm to 250mm* 100mm.
Struts
Horizontal members holding the poling boards or waling apart, usually placed some 1.8m to 2m apart to allow for working room.
In all cases of timbering, the work should be carried out in such a way that the operatives installing the timbers are not subject to the risk of trench collapse. They should operate from within the safety of the existing timbering or some cage which effectively protects them.
