Investigation of the failure of permanent anchorages adjacent to a tidal surge barrier

To provide protection against flooding of densely populated areas, a tidal barrier and anchored sheet pile walls were constructed as part of overall flood protection scheme across a tidal estuary in England. The piled structures, completed in 1979, were supported by thirty four, 48m long permanent ground anchorages installed below the capping beam at an angle of 40 degrees to the horizontal.

In September 1991 a 25m length of the pile wall was subject to a lateral deflection of up to 450mm at the pile head. The paper describes the visual examination of the wall, exhumation behind the wall to anchorage level and inspection of the exposed anchorage components. These included failure of the anchor tendon and pull out of the tendon from the anchor head. In addition there were indications of the use of inappropriate construction techniques employed at the time of installation.

Given anchored structures of similar type and age exist at many UK locations, there is concern that similar standards of construction and design specification may have been adopted elsewhere. By highlighting the features faced at this site, the paper gives an insight into the issues that could potentially be presented in other structures and provides recommendations on forward strategies that could be adopted to prevent failures in the future.

• Introduction

• Structure and movement

• Initial Inspection

• Construction and Construction Techniques

• Corrosion protection provided and standards at time of construction

• Overall examination

• Detailed Examination

• Summary and Recommendations

• References