Examination of Economical Methods for Repairing Highway Landslides

The Kentucky Transportation Cabinet (KyTC) spends millions of dollars each year in the repairs of highway landslides. In previous research, an inventory of highway landslides showed that about 1440 landslides of various sizes exist on major roadways maintained by the KyTC. Moreover, emergency repairs can exceed one million dollars for large embankment failures. In many instances, drilled-in, or driven, railroad steel rails were frequently used as a stop-gap measure to halt landslide movements or those efforts were tried as a permanent solution. The use of rails to serve as a restraining structure was usually not successful when the height of fill exceeded about 20 ft. The previous study also showed about 39% of the landslides were small and less than 20 ft in height. Cost estimates indicated that railroad steel rails, when drilled and socketed into bedrock, may be effective and economical when the embankment height is less than about 20 ft. This study had two major objectives. Because railroad steel rails are widely used, the development of a theoretical method of analyzing and predicting the success of rails that are drilled-in and socketed into bedrock was a major objective. To enhance this method and possibly extend the height that this technique may be used, theoretical equations were developed that include the use of lightweight backfill materials, such as geofoam, shredded tires, bundled tires, "red dog," and byproducts from coal-fired power plants. Backfill materials with different unit weights, and existing in a layered system, may be analyzed. To facilitate the use of the approach and make it widely accessible to KyTC engineers, and as a second major objective, the theoretical algorithms were programmed in a Windows computer program and stored in the Kentucky Geotechnical Database. The twelve highway district offices and main central offices of the KyTC are connected in a client server system. For a selected factor of safety, the program predicts the success of drilled-in rails so that the user may avoid using this technique when the factor of safety is not adequate to prevent failure. However, when failure is predicted using the unit weights of ordinary soil, or rock, backfill, the program shows the thickness of geofoam (or other lightweight material) necessary to increase the factor of safety to a value greater than one. The program has been checked by comparing results with results obtained from a program written by KyTC. Several examples are performed to illustrate the use of the new computer program.