Maintenance Control of Ground Anchors Constructed in Japanese Expressways

Cut slopes on expressways are under extraordinarily severe conditions in Japan because approximately 70% of land is composed of unstable soils and thus frequently influenced by typhoons and earthquakes. Ground anchors have recently been adopted on numerous occasions for slope stabilization. Ground anchors have been in service for slope stabilization on expressways in Japan for approximately 40 years. Cases of fracture of ground anchors with inadequate corrosion protection (old-type ground anchors) on expressways in 1987 revealed the deformation of ground anchors due to corrosion. At present, ground anchors are applied with better corrosion protection. In the future, however, appropriate maintenance of ground anchors including those with inadequate corrosion protection, and the identification of life-cycle cost will be required.

This paper describes the functional deterioration of old-type ground anchors due to corrosion that was revealed as a result of investigations of anchors collected at six locations to detect the functional deterioration of old-type anchors. The paper also presents ground anchor maintenance standards on expressways. For investigations of the integrity of ground anchors, refer to another paper.

• Investigation outline

• Investigation results

• Maintenance

• Conclusions

• Closing remark

• References