Bengt B Broms & Bertil Nord. This paper was first published in GE’s October 1985 edition.
A new type of ground anchor, which makes use of expander bodies and has been developed by Atlas Copco MCT, Sweden, can be employed for the support of sheet pile walls, slurry trench walls etc. under different soil conditions.
The new anchor consists in principle of a folded thin steel sheet, the expander body, which can be inflated in the ground through the injection of cement grout as shown in Fig. 1. The anchor is either pushed into the soil or placed in predrilled cased holes depending on the soil conditions.
The volume of the grout required for the expansion and the corresponding pressure are measured in order to check the ultimate resistance of the anchors. The maximum grout pressure that can be applied is 3-4MPa.
The thin steel sheet gradually unfolds as the expander body is inflated when the cement grout is injected through a separate grout pipe as illustrated in Fig. 2. The total length of the body is thereby reduced. The soil around the expander body becomes compacted and preloaded and only a small deformation will be required to develop the maximum resistance when it is loaded.