Performance Evaluation of Highway Slopes on Yazoo Clay

Slope failures are frequent in highway embankments on expansive Yazoo clay in Mississippi due to frequent seasonal rainfall events associated with temperature and humidity variation causing expensive maintenance problems for the Mississippi Department of Transportation (MDOT). This State Study 286 was conducted to understand the performance of highway slopes containing Yazoo clay. Six repaired highway slopes were instrumented comprehensively to monitor the moisture, matric suction, and temperature variation, as well as monitoring the slope deformation using vertical inclinometers. Besides field monitoring, numerical modeling using the Finite Element Method (FEM) was conducted to evaluate the effect of rainfall frequency and duration (based on historical rainfall data of Mississippi) on the water infiltration and corresponding change in the factor of safety of the highway slope. Based on the field monitoring results, the data of volumetric moisture content and matric suction readings were observed constant throughout all six slopes. Certain peaks and drops in the moisture content were also observed during the summer months. The numerical modeling analyses indicates the rainfall during late summer to early fall is the most critical time in which a perched water condition will develop. As the wet-dry cycle soften the shear strength of high plastic clay to fully softened state the presence of perched water creates a slope condition vulnerable to a creeping slide failure. Based on this research, it is observed that slope failures of Highway embankments containing highly plastic clays such as Yazoo clay takes place due to the development of perched water conditions after five to seven years of construction. It is highly recommended to consider including a perched water zone up to the depth of the active zone along with the development of fully soften shear strength condition in the slope stability analysis of any slope containing high volume change clays, such as Yazoo clay

• Record URL:
  https://mdot.ms.gov/documents/Research/Reports/Interim%20&%20Final/State%20Study%20286_Final%20Report.pdf
• 
• Record URL:
  https://rosap.ntl.bts.gov/view/dot/56232
• Corporate Authors:

  Jackson State University, Jackson

  Department of Civil and Environmental Engineering
  Jackson, MS  United States  39217-0168

  Mississippi Department of Transportation

  Jackson, MS  United States  39215-1850

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Khan, Mohammad Sadik
  • 0000-0002-0150-6105
  • Amini, Farshad
  • 0000-0003-2899-0045
  • Nobahar, Masoud
  • 0000-0001-8457-7234
• Publication Date: 2020-6-30

Language

• English

Media Info

• Media Type: Digital/other
• Edition: Final Report
• Features: Appendices; Figures; Maps; Photos; References; Tables;
• Pagination: 254p

Subject/Index Terms

• TRT Terms: Clay soils; Deformation; Embankments; Finite element method; Moisture content; Rainfall; Shear strength; Slope failure; Soil suction; Swelling soils
• Geographic Terms: Mississippi
• Subject Areas: Design; Geotechnology; Highways;

Filing Info

• Accession Number: 01747130
• Record Type: Publication
• Report/Paper Numbers: FHWA/MDOT-RD-20-286, 286
• Contract Numbers: SPR-2017(028)/107691-1011000
• Files: NTL, TRIS, ATRI, USDOT, STATEDOT
• Created Date: Jul 30 2020 3:49PM