Slope Stabilization with Rock Anchors and Slope Drains, Act 2 - Del Webb Community, Mt. Juliet, TN-PPT Presentation

PPT Presentation

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The Del Webb Community in Mt. Juliet, Tennessee, experienced repeated failures of a site-development fill slope, particularly after wet weather. An initial rock buttress (“Act 1”) did not provide adequate stability. A new project team investigated the slope and found soft soils, silty seams, organic material, and laboratory samples with very low shear strength.<br /><br />The “Act 2” design combined rock anchors, slope drains, drainage improvements, and crest reconstruction. Analyses indicated a factor of safety of 1.1 under normal groundwater conditions and 0.7 under high groundwater conditions with the existing buttress. The completed design, with anchors and controlled groundwater, was modeled at 1.7. Construction-stage analysis also confirmed acceptable stability while drilling with air, at a factor of safety of 1.2.<br /><br />At the contractor’s request, 37 precast concrete reaction blocks replaced the planned continuous shotcrete beam. Crews installed corrosion-protected anchors, tested them to 320 kips, and locked them off at 240 kips. Where fractured rock produced lower-than-expected bond stresses, anchors were extended or replaced until they passed testing. Eleven drilled slope drains and three remotely monitored load cells were also installed.<br /><br />Work took 3.5 months and cost $1.8 million. Key lessons included the value of a strong multidisciplinary team, considering contractor experience, assessing drilling methods for their effect on stability, and allowing for field adjustments.

Keywords

Del Webb Community

Mt. Juliet Tennessee

slope failure

fill slope

rock buttress

rock anchors

groundwater drainage

slope stability

construction remediation

geotechnical engineering