Site: Kajiwara Section, Meishin Expressway
Osaka, Japan
Date Visited: October 1996
Owner: Highways Corporation
Osaka Construction Bureau
Contact: M. Kamiyoshi, Project Manager, Teijin, Ltd.
Summary: 36 aramid fiber reinforced tendons were used as ground anchors for slope stabilization.

ACTIVITIES OF INTEREST

Thirty six aramid fiber reinforced ground anchors were used on a small portion of the Meishin Expressway in 1994, as a demonstration of the viability of using nonmetallic anchor rods during the widening of the roads. The section chosen had electric power pylons at the crown of the slope, necessitating solid stabilization to ensure no slope movement. The anchors consist of bundles of 9 spiral wound AFRP rods of 7.4 mm diameter (42.4 mm2 nominal cross-sectional area, 62 g/m unit weight and a guaranteed breaking strength of 7,630 kgf) in an overall configuration as shown in Figure B.120.


Fig. B.120. Configurational details of an AFRP ground anchor.

The top of the anchor consists of a bond type anchorage filled with non-shrink mortar, a protection cap and pipe. The entire housing is fabricated of stainless steel and is fixed to a bearing plate with nuts. The free anchor length is sheathed in a polyethylene tube, which is connected at one end to the stainless steel anchorage protection pipe. A similar anchorage exists at the end of the ground anchor. The assembly is such that conventional installation techniques can be used with anchoring performed by the bond between the cement grout and the aramid rods in the fixed anchor length and by frictional resistance between the grout and the ground. Figure B.121 shows the 36 ground anchors each with a design stabilizing force of 400 kN. Anchors ranged in length from 19 m to 30 m and were placed as shown in the schematic in Figure B.122.

Each anchor had a fixed length of 6.5 m and a fixed bore diameter. The rods were tensioned to a force of 0.75% of ultimate, resulting in a level of 0.6% Pu at transfer and under design load. Pressure plates for this application were fabricated out of specially fabricated composite channel sections. Overall length of the anchor bars was 8.3 km.


Fig. B.121. View of the anchored slope showing FRP pressure plates.


Fig. B.122. Schematic of slope section


Published: October 1998; WTEC Hyper-Librarian