Environmental Engineering Reference
In-Depth Information
- Depend on their self weight to close the grab. Pulleys or hydraulic systems are used
to assist in closing;
- Can be used up to 75 m (cable operated), or 55 m hydraulic.
(b) Kelly bar which:
-Are better suited to homogeneous soils;
- Have a maximum depth of 40 m (single piece Kelly) telescoping up to 60 m;
- Requires large headroom;
-Are hydraulically or power operated, with the Kelly bar weight assisting to close
the bucket.
Other types of excavation equipment which can be used include:
(c) Bucket scraper. This is attached to a Kelly bar as shown in Figure 10.25;
(d) Rotary drills
In this technique the excavation is carried out by a drill which has several bits
mounted on a submersible frame. Figure 10.26 shows one type of such equipment.
Figure 10.25.
Action of a scraping bucket excavator (Xanthakos, 1979, reproduced with permission of
McGraw-Hill).
Figure 10.26.
Rotary drill technique (Xanthakos, 1979, reproduced with permission of McGraw-Hill).
