25. Especial care should be taken, especially in cities, to properly protect the adjoining property, sidewalks, etc. from injury by the caving in of the bank during excavation.

To guard against this, the banks or sides of the excavation are sheet piled, as shown in Fig. 1.

Sheet piling consists of a plank cut to a point at the lower end, placed closely in line, and driven into the ground against the bank of the excavation, as shown at (a), Fig. 1, which is a front elevation of sheet piling. At a is shown the piling driven into the cellar bottom b, against the bank of the excavation. At (b) is a section across the piling to show the braces d placed against the batten e to retain the piling in place against the earth pressure at the top. The stake shown at f is driven in to keep the brace d from slipping. These braces are usually spaced about 10 or 12 feet apart, and are necessary when the excavation is a deep one.

Protection Of Excavations 1

Fig. 1.

26. When the foundations of a new building go below those of the adjoining property, the adjacent walls must be underpinned, the method of doing which, will be described in a subsequent section.