Geotextiles are frequently used for subgrade improvement under roadways. Caltrans has released a document titled "Guide for Designing Subgrade Enhancing Geotextiles". This 18-page document covers what situations can be improved using geotextiles and includes a flowchart for guidance on when to apply them and for what purposes. From Geosynthetics magazine. (Image by Caltrans)
In this ENR.com video, a US Army Corps of Engineers (USACE) project to protect Grand Isle Louisiana from the erosional effects of a large storm surge is described. 5.7 miles of sand filled geotextile tubes or geotubes 30-ft in diameter are used to form the core of a dune along with a geotextile erosion apron held in place by anchor tubes. The design is aimed to prevent devastating erosion in the event that a large storm surge overtops the protective dunes. The sand is screened on site and mixed with water to form a slurry that is pumped into the tube. Once the tubes are in place, additional sand will be placed over the top and the dune revegetated. If the topping sand is eroded away, the Corps hopes the fix will be easier to perform with the tubes. Click through for the video.
The site for the new Harrison County Hospital, approximately 25-miles west of Louisville, Kentucky had 15 sinkholes formed by limestone dissolution, a geomorphologic process referred to as Karst topography. There were a number of geotechnical engineering and geological engineering challenges associated with the characterization, excavation, backfilling, foundation engineering and other mitigation measures as described by Peggy Hagerty Duffy, P.E. in her article entitled “Karst and Complications” in the August 2008 issue of Civil Engineering Magazine (Duffy, 2008b).
Mitigation measures for the sinkholes included use of graded filters with geotextiles, careful inspection of rock socket foundations along with pilot holes and careful geotechnical inspection throughout the construction process. One particularly interesting aspect of the project is that several of the sinkholes were used as drainage facilities to receive surface water runoff. Read on for a summary of this interesting article. (Photo of sinkhole in Karst Topography being used as a drainage feature, from Duffy (2008b), Civil Engineering Magazine)