Determination of Spatial Variation of Unsaturated Vertical Permeability

Moisture flow through unsaturated soils causes numerous geotechnical problems. Specifically, moisture plays an important role in the volumetric deformation of expansive subgrade soils. Hydraulic conductivity can be an effective tool for tracing the spatial variation of moisture flow. This spatial variation of moisture flow may help to indicate areas more susceptible to volumetric deformation. Direct measurement of unsaturated permeability in the laboratory can be used to simulate the field conditions, but it is time-consuming and complicated. While there are some established methods for field determination of saturated hydraulic conductivity, direct measurement of unsaturated permeability in the field is very limited. From this, another method for determining the unsaturated permeability in the field is desired. In this study, an attempt was undertaken to determine the variation of unsaturated hydraulic conductivity based on rainfall response data. Moisture sensors were installed at different depths beneath the pavement and side slope of a state highway in Dallas, TX. It was observed that the response of the moisture sensors due to rainfall varies with sensor depth. That is, deeper sensors had a more delayed response time than shallower ones. In addition, a time lag was observed between the sensors located at different points along a horizontal line. In other words, sensors farther from the side slope reacted later than those closer to the side slope. Knowing the distance, using the time required for the moisture to move from one point to another point, the unsaturated hydraulic conductivity was determined. Based on the preliminary results, it was found that unsaturated permeability values varied from 10−⁴ to 10−⁵ m/s.


  • English

Media Info

  • Media Type: Web
  • Features: References;
  • Monograph Title: PanAm Unsaturated Soils 2017: Fundamentals

Subject/Index Terms

Filing Info

  • Accession Number: 01683232
  • Record Type: Publication
  • ISBN: 9780784481684
  • Files: TRIS, ASCE
  • Created Date: Oct 4 2018 5:01PM