When sewer pipes crack and leak, the surrounding ground becomes saturated and soil can migrate into the pipe and leave behind a void. Eventually this void can expand until it undermines the pavement or other structures forming a sinkhole. The same ground penetrating radar technology being used by geophysicists to perform subsurface characterization and by the military to detect roadside bombs in being adapted to detect these voids before they reach the surface. Researchers at Louisiana Tech University are developing a robot to traverse sewer pipes and scan around the pipe for potential voids using the GPR. The research is being performed with $3M from NIST and $3.2M from Cues, Inc. a Louisiana sewer inspection company. Additional trials are slated to take place this month. [Source: NOLA.com. Image: AP File Photo/Mark Was via dailyreporter.com]
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)
Boulder, CO, USA â€“Studying the arrangements of sediments and sedimentary rocks in Earth’s near-surface layers received a recent boost from a new volume published by the Geological Society of America. Stratigraphic Analyses Using GPR, GSA Special Paper 432, offers a state-of-the-art overview of ground penetrating radar applications in the field of shallow subsurface stratigraphic analysis. [more…]