Dakota-Federal 42X-36 Well Pad Stabilization-PPT Presentation

PPT Presentation

Pdf Summary

The Dakota-Federal 42X-36 well pad in North Dakota was built in 2009 within a mapped landslide hazard area. The pad was cut into and built over soft, claystone-dominated Sentinel Butte Formation, which is prone to seepage and landslides. Monitoring from 2020 onward detected movement, while a wet winter and a rise in pore-water pressure—particularly in a deep lignite layer—prompted a stabilization plan.<br /><br />The design used a 705-foot-long, 16-foot-high anchored soldier pile wall to retain the pad. It included 95 drilled shafts and 190 hollow-bar anchors arranged in upper and lower rows. The downslope slope outside the wall remained unimproved, with a calculated post-stabilization factor of safety of 1.25.<br /><br />Construction began in May 2022. On June 17, before the piles were anchored, the landslide remobilized: three piles shifted 3 to 4 feet downslope, accompanied by extensive cracking and ground movement. Emergency measures included unloading the failure area by cutting it down 7 feet and installing 98 sacrificial HP piles downslope of the wall. Construction then resumed, with drilled shafts completed in June and anchors installed from July to August. The pad was restored with geogrid, a polyethylene liner, and finished grading; the project was completed in September 2022.<br /><br />Monitoring included visual inspections, surveys of selected piles and ground points, and slope inclinometer readings. The schedule was monthly through August 2023, quarterly through August 2024, and annual beginning in August 2025.

Keywords

North Dakota

Dakota-Federal 42X-36

well pad

landslide hazard

Sentinel Butte Formation

anchored soldier pile wall

drilled shafts

hollow-bar anchors

slope stabilization

monitoring