Study of a Pipe-Scanning Robot for use in Post-Construction Evaluation during Horizontal Directional Drilling

Trenchless Technology has become an increasingly popular underground utility construction method, beginning in the early 1900s with pipe jacking beneath railroad lines. One method, horizontal directional drilling (HDD), became more common in the 1990s and into the current day. The utilization of HDD is associated with the potential risk for ground subsidence, soil heaving, sinkholes and settlement after construction. This can damage existing infrastructure and cause safety hazards. Trenchless methods, requiring an annual overcut – such as HDD, disturb soil around the outer diameter of the utility being installed. While the annular overcut is necessary for feeding pipes through the borehole, when used in conjunction with a liquid lubricant, the likelihood for developing voids increases. The annular overcut is also a cause for concern because the consistency and void ratio of the overburden soil change after boring. Inconsistent and void-ridden soil can cause void propagation through the overlying soil until it reaches the surface, where it will become a sinkhole or crack. This paper addresses post-construction evaluation methods, especially pertaining to the annular space and void propagation region above and around a freshly installed utility in Southern Virginia. Two non-destructive evaluation methods are used to scan the surrounding soil: Ground penetrating-radar (GPR) and FutureScan. FutureScan, a radar device developed by Louisiana Tech University, is capable of being attached to pipe inspection robots and uses a means of penetrating radar to detect voids and inconsistencies in three dimensions. This study examines the difference between GPR and FutureScan, regarding the imaging techniques used and the measured void ratios. Relative elevations were recorded before, during, and after drilling, to measure surface movement caused by drilling efforts. The relative elevation was also recorded several months after utility installation, for comparison on a long-term scale. After the analysis was conducted using both FutureScan and GPR, representative soil samples of the test site were retrieved and transported to a geotechnical laboratory for further testing. Based on the GPR and FutureScan findings, the utility of the two post-construction evaluation methods was determined.


  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Figures; Photos; References; Tables;
  • Pagination: 49p

Subject/Index Terms

Filing Info

  • Accession Number: 01610817
  • Record Type: Publication
  • Report/Paper Numbers: UVA 2013-05
  • Created Date: Sep 2 2016 8:11AM