Long Term Monitoring and Routine Maintenance of Ground Anchorages at Devonport Royal Dockyard, Plymouth U.K.

maintenance of the UK's fleet of Nuclear Submarines. To allow this to take place, between 1995 and 2002 the existing docks and associated structures were upgraded to modern nuclear standards of seismic qualification. Part of this upgrade required the installation of 247 multistrand anchorages with a working load of 3150kN, and 531 Bar anchorages with a working load of 2040kN.

This paper presents the findings from the current maintenance regime, discusses how such a regime can provide confidence in the anchorage performance and thus the structures fitness for purpose.

The continued monitoring and maintenance at Devonport Dockyard has provided a high level of confidence in the anchorages and thus the structures that rely on them. Lift off checks have confirmed the general findings of load cell trends although some anomalies mean that periodic lift off checks are still required. Corrosion monitoring via visual inspections has proved successful for identifying corrosion and carrying out remedial action. It is noted that potential corrosion below the anchor head is possible, however research into non-destructive testing and trials of some methods have been fruitless. Confidence in the double corrosion protection and endoscope surveys where possible should provide enough confidence in the corrosion protection system.

• Background

• Purpose of Routine Maintenance

• Review of Standards

• Maintenance Techniques Employed

• Results of Maintenance and Monitoring

• Conclusions

• Recommendations

• References