Vertical moisture barriers have been used in numerous locations in Texas to minimize damage associated with expansive clays. Most of the applications use an impermeable fabric 2.4 m (8 ft) deep installed in narrow trenches at the edge of the highway. If the barrier is working correctly it should stabilize the subgrade moisture content inside the barrier. Attempts to measure barrier effectiveness have frequently caused problems because of the unreliability of moisture-measuring sensors. An attempt to monitor a barrier is made with the Troxler Sentry 200-AP device. This capacitance-measuring system requires the installation of a polyvinyl chloride pipe 51 mm (2 in.) in diameter both inside and outside the barrier. The capacitance readings made inside the tubes are converted to moisture-content readings by a laboratory calibration procedure. The system is demonstrated on a major moisture barrier project on I-45 in which 90 km (56 mi) of barrier are being installed. To date the Troxler system is working well. The 2.4-m barrier appears to be effective in stabilizing the moisture content of the top 1.5 m (5 ft) of subgrade. Below that depth the moisture contents inside and outside the barrier are similar.


  • English

Media Info

  • Features: Figures; Photos; References; Tables;
  • Pagination: p. 10-20
  • Monograph Title: Environmental moisture effects on transportation facilities and nonearth materials' thermal effects on pavements
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00712975
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Oct 10 1995 12:00AM