Date of Award
Bachelor of Science (BS)
Dr. John R. Reid
The Sunny Slide area is in east-central Morton County, 4.6 road miles west of Mandan, North Dakota. The area of study measures 1900 feet by 800 feet and includes U.S. Highway 10 and the Burlington Northern Railway ' s central line, both threatened by continuing slope failure. The present episode of local instability dates back to the Spring of 1953.
Field reconnaissance of the surface, including thirty-two shallow test holes, provided data on surface lithology as well as basic groundwater information. Seven subsurface holes were correlated with inclinometer data to enable lithologic descriptions of the zone of shear.
The Cannonball Formation (Paleocene) is present, at the surface, throughout most of the area. The dominant lithology is poorly consolidated sandstone and mudstone. The zone of shear is located within the mudstone or at the upper contact of it and an overlying silty clay.
Field data and precipitation records indicate water to be the major contributing factor to failure in this area. Evidence strongly supports the existence of a large pre-1880 slide, or series of slides, throughout much of this area. The highway is located on the slumped material, and the railroad is near the toe of the slide.
A detailed groundwater study should be undertaken in this area before any new corrective measures are installed. Possible corrective measures include: installation of pumping wells, horizontal "gravity" drains, addition of "quick" lime into the subsurface, and e1ectro-osmosis. The decision on which one (or combination) to use should await the results of the detailed groundwater (piezometric) study.
Murphy, Edward C., "The Geology and Geohydrology of the Sunny Slide Area Mandan, North Dakota" (1979). Undergraduate Theses and Senior Projects. 73.