5 SHORING AND TIMBERING
5.1 General
5.1.1 All trenches in soil more than 1.5 m deep shall be securely shored and timbered.
5.1.2 All trenches in friable or unstable rock exceeding 2 m in depth shall be securely shored and timbered.
NOTES
1 The above requirements do not apply in cases where the sides ofthe trenchesaresloped to within 1.5 mofthebottom. Theslope that is provided forsuch purposesshall be inspected and certified as stable by the persons in charge of work in all cases.
2 Notwithstanding anything said above, it shall be understood that the need for shoring is a matter which shall receive careful and frequent consideration even in trenches less than 1.5 m or 2 m in depth (as the case may be) and where there is any doubt as to the safety of the work without shoring, no further excavation or other work shall be continued until adequate shoring is provided.
5.1.3 Where the sides of trenches are sloped as specified in 5.1.2 but not to within 1.5 m of the bottom, the vertical sides shall be shored and the shoring shall extend at least 30 cm above the vertical sides.
When open spaced sheathing is used, a toe board shall be provided to prevent material rolling down the slope and falling into the part of the trench with vertical walls.
5.1.4 Shoring and timbering shall be carried along with the opening of a trench but when conditions permit, protection work, such as sheet piling may be done before the excavation commences.