Post Grouted Single Bore Multiple Anchors at Hodenpyl Dam, Michigan

Abstract

Despite the installation of a row of anchors in 1996, the right downstream retaining wall of Hodenpyl Dam, MI, continued to move inward and downstream. The remediation design called for installation of additional anchors. However, there were concerns about creep-induced relaxation of the anchor load over time given the existence of high-plasticity clays at the site. The solution was the installation of post grouted multi-anchors along the base of the retaining wall (Single Bore Multiple Anchors -SBMAs).SBMAs utilize several "unit" anchors within the same borehole, each with its own short efficient bond length positioned at staggered intervals along the bond zone. This staggered arrangement allows each unit load component to be transferred to the soil in a controlled manner over a discrete length of the borehole, thereby producing a very efficient load transfer mechanism. A larger factor of safety against creep is therefore attainable using SBMAs as compared to that provided by conventional tendons.One sacrificial anchor and 13 production anchors were installed. An innovative testing setup and program were developed to allow extended creep testing of the sacrificial anchor followed by load testing to 2.8 times the design load without anchor failure. This paper describes the design and construction of the SBMAs, the load testing setup, and results of extended creep load testing. 1.

Archives of Civil Engineering

“…There are many examples of successful application of the Single Bore Multiple Anchor technology around the world. Its creep reducing properties were proven by extended creep tests in Hodenpyl Dam in Michigan [25] and Kuntsevo Shopping Centre in Moscow [11]. Permanent SBMA anchors were part of Hunter River Remediation Project in Newcastle (Australia) and as a slope stabilisation solution in A2 motorway in Austria [11,26].…”

Stabilization of Retaining Wall Along Tailrace Channel of Hodenpyl Dam

“…The paper also includes an evaluation of the performance of the SBMA system based on monitoring and inclinometer data before and after stabilization. Details regarding the design, installation, and testing of the SBMA system are given in a companion paper by Bruce et al (2004). Figure 2 shows a cross section of the east tailrace wall.…”

“…In this system, the bond length comprises a set of shorter and staggered individual unit anchors, each of which is fitted with one or more strands and is tensioned using an independent jack (see Figure 5). A more detailed description of the SBMA system is presented in a companion paper by Bruce et al (2004).…”

“…In addition, two performance tests (PTI 1996) were carried out on production anchors. Details of procedures and results from the sacrificial and production anchor tests are presented in the companion paper by Bruce et al (2004). The test results indicated that the required capacity of the tiebacks could be achieved and that creep would not be an issue.…”