Measurement of In Situ Soil Water Characteristics Curve Using Data Analysis

Soil Water Characteristic Curve (SWCC) is an essential tool to determine the properties of unsaturated geomaterials, including shear strength, permeability and volume change. Although many laboratory measurements of SWCCs are available in the literature, field studies of the subject are very limited. In the current study, six (6) series of sensors were installed in the field at different depths and locations. The sensors measured moisture content and suction of the soil every hour for a period of about three years. A Visual Basic (VB) code was developed to analyze the data and extract the field SWCC. In addition, undisturbed samples were collected and the SWCC was measured in the laboratory under different overburden loads. The field and lab measured SWCC were later compared to determine the possibility, accuracy and precision of the field measurement. It was concluded that instrumentation should be performed at a depth deeper than surficial cracks and daily moisture content fluctuation, but not so deep that moisture variation is very limited. The best depth of installation was determined to be about 2.5m below the existing ground surface at the site of the study. The field SWCC showed very good compatibility for the range of suction below the Air Entry Value (AEV) of the soil, but reported lower moisture contents that the lab for suctions greater than AEV. The AEV between lab and field were measured at 110 kPa and 120 kPa, respectively. It was also concluded the normalized water content (i.e. degree of saturation) shows better comparability rather than the volumetric water content. In addition, among the three van Genuchten parameters (a, n and m); a and m were found in close vicinity whereas the n parameter had a large margin of difference, which was determined to be due to disturbance of the native material during instrumentation.

• Supplemental Notes:
  • This paper was sponsored by TRB committee AFP60 Standing Committee on Engineering Behavior of Unsaturated Geomaterials.
• Authors:
  • Hedayati, Mahsa
  • Ahmed, Asif
  • Hossain, Md Sahadat
  • Hossain, Jubair
• Conference:
  • Transportation Research Board 97th Annual Meeting
  • Location: Washington DC, United States
  • Date: 2018-1-7 to 2018-1-11
• Date: 2018

Language

• English

Media Info

• Media Type: Digital/other
• Features: Figures; Photos; References; Tables;
• Pagination: 22p

Subject/Index Terms

• TRT Terms: Data analysis; Field tests; Moisture content; Physical properties; Soil water
• Subject Areas: Geotechnology; Materials; Transportation (General);

Filing Info

• Accession Number: 01657893
• Record Type: Publication
• Report/Paper Numbers: 18-04319
• Files: TRIS, TRB, ATRI
• Created Date: Jan 25 2018 9:33AM