A midstream transmission group asked GSI® to look at an urgent slide on this large cross-country natural gas transmission line. The slope appeared to have been disturbed by landowner excavation activities, causing a large landslide. The earth movement caused nearly four feet of horizontal deformation of the line spanning more than 175 linear feet, putting the 24 inch high pressure line in danger of imminent rupture. GSI® completed a field survey along with other measurements and photographs. This data was used to produce field sketches, then developed into an estimate, and eventually turned into a global stability model to verify the field observations, and initial conceptual design approach. GSI® engineers accomplished their site visit, all modeling, and design within three days at no cost. The initial design called for multiple rows of up to 40 foot long Self-Drilling SuperNails® and a reinforced shotcrete panel both above and below the active pipeline. During construction, GSI® crews encountered bedrock at shallower than expected depths in some locations, allowing GSI® engineers to re-model and revise the design to include shorter SuperNails®. The refined design saved the client nearly 30% over the original proposal.
In the Mid-Atlantic Region of the United States a rockslide occurred that presented a variety of problems for the state’s Department of Transportation (DOT).