Concrete Trench Fill.

Concrete trench fill consists of a mass concrete strip cast into the open trench making use of the trench sides as a shutter (see Fig. 9.5).

Concrete trench fill is often used where strip loads are required to be transferred to relatively shallow depths
through soft material which is capable of standing up, without extra support, for at least a period adequate to cater for the construction sequence to be adopted. The trench fill can embrace requirements for heavy loads going down to rock or light loads on soft sub-strata (see Fig. 9.6).

The requirement for working space within the trench  for bricklayers is not a factor in determining the width of excavation with this method. Pouring concrete to within 150 mm of ground level overcomes this consideration.

Fig. 9.5 Concrete trench fill.

Fig. 9.6 Concrete trench fill.