Repeated Lift-Off Testing of Single Bore Multiple Anchors for Dam Retaining Wall over a 5-Year Period

The right downstream retaining wall of Hodenpyl Dam in Michigan had undergone significant lateral displacement due to global instability of the in situ soils. The remediation design called for installation of additional anchors bonded within a high plasticity, stiff clay layer. To increase the unit bond strength and reduce the potential for creep observed in other anchors installed at the dam, the contractor selected the Single Bore Multiple Anchor (SBMA) system with intensive, selective post grouting. The SBMA anchors have been lift-off tested four times since their installation. This paper describes the design and construction of the SBMA anchors, testing of a sacrificial SBMA anchor, lift-off testing procedures and results, and conclusions.