Service Performance of Multiple Anchors in difficult ground conditions for both Permanent Anchors and Temporary Removable Anchor usage

At the site location in Ashford, Kent, the underlying Hythe Beds typically consist of alternating layers of hard sandy limestone and weakly cemented sandstone interspersed by beds of silts or clays of variable thickness. The irregularity of the strata made preliminary anchor design difficult since it was not possible to predict that inclined wall retention anchors distributed around the site would encounter either rock bands or entirely clay within the proposed fixed length. The multiple anchor design offers flexibility which is particularly beneficial in such varied ground conditions.

Both permanent anchors and temporary anchors were required to support sides of the secant pile wall cofferdam. Furthermore the full length tendons were required to be removed from the temporary anchor borehole when the adjacent structural works were complete. The satisfactory performance of each and every individual anchor (typically 4 “units” per anchor) in compliance with the acceptance criteria for both load/extension behaviour and creep characteristic is described. Temporary anchors were load checked during the service period and prior to successful removal of the anchor tendons

• Introduction

• Ground Conditions Fixed Length Design and Supplementary Safeguards

• Tendon Systems

• Performance in Service

• Summary and Recommendations

• Acknowledgments

• References