Reconnaissance-Level Laser Scan of Highway Surface Revealed Slight Depression above Buried Pipeline

A reconnaissance-level laser scan survey conducted as part of a consulting project to repair subsurface voids above two pipelines crossing a major divided highway revealed a slight depression across one of the lanes. The two pipelines were installed with jack-and-bore methods approximately 10 years apart. The repair project was initiated immediately after sinkholes were discovered by the pipeline company. The initial response was to fill sinkholes with surface soils or flowable fill. A geotechnical investigation, accomplished with vacuum truck probes and one test pit, revealed voids and a program of grouting with limited-mobility displacement grout was recommended to fill voids and compact loose soil. Grouting was accomplished in vertical pipes in the northbound lanes and parts of the median and shoulder. Grout pressure criteria and local manometer readings on the ground surface were used to minimize expected ground heave. Reconnaissance-level laser scanning of the highway surfaces was performed before and after grouting to document potential grouting-induced elevation changes. Arbitrary coordinates were used for the scanner surveys, the locations of which were related to distinctive features on nearby steel lattice electrical transmission towers. Error in the laser scan data varied with distance from the scanner setup location and was attributed to windy conditions, including air blasts generated by passing vehicles. Both sets of laser scan survey data showed that the grouting caused no detectable change in the road surface elevation. The laser scan survey revealed a slight depression in one the highway lanes over one of the pipelines at a location that was not identified by visual examination of the highway surface or adjacent to voids encountered in vacuum probe holes. The largest amount of grout (4.05 m³) injected at a single point on the entire void-repair project was in the shallow depression revealed by the laser scan survey.


  • English

Media Info

  • Media Type: Web
  • Pagination: pp 3070-3088
  • Monograph Title: GeoCongress 2012: State of the Art and Practice in Geotechnical Engineering

Subject/Index Terms

Filing Info

  • Accession Number: 01530359
  • Record Type: Publication
  • ISBN: 9780784412121
  • Files: TRIS, ASCE
  • Created Date: Nov 12 2013 2:06PM