Case History - Landslide Stabilization Using Strand Anchor Block-PPT Presentation

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The Breaks Substation in Elkhorn, Kentucky, was built around 2015. Shotcrete walls were installed to address a landslide during construction, but a new landslide occurred in March 2021. The slide extended about 330 feet across roughly one acre, damaging structures and retaining walls and potentially threatening the substation, railroads, access road, drainage features, and nearby environmental areas.<br /><br />Survey monitoring showed that movement varied with seasonal and weather conditions. Borings and slope inclinometers identified a shear zone approximately 20–30 feet deep, with bedrock ranging from 30 to 100 feet below the surface and deep boulder-rich colluvium above it. The colluvium was considered potentially unstable, possibly reflecting an ancient landslide formed under wetter conditions.<br /><br />Because conventional measures such as soil nails and anchored wire mesh offered limited capacity for this deep-seated slide, the project used four rows of strand anchors connected to concrete blocks. Anchors were designed to extend into bedrock, with working benches provided for installation. Key design considerations included anchor direction and spacing, corrosion protection, water testing, block design, load testing, lock-off loads, and bearing capacity in near-surface colluvium.<br /><br />Construction included temporary slope stabilization, anchor drilling and water testing, load testing and tensioning, and placement of precast blocks. Monitoring indicated that movement slowed or stopped after the anchors and blocks were installed.<br /><br />Lessons learned included the need for thorough geotechnical investigation at sites with ancient landslides, experienced contractors, adequate construction access, allowance for anchor-material lead times, and careful planning for anchor interference and construction tolerances. Water testing also helped assess rock quality.

Keywords

Breaks Substation

Elkhorn Kentucky

landslide stabilization

shotcrete walls

deep-seated slope failure

strand anchors

concrete blocks

geotechnical investigation

bedrock colluvium

anchor load testing