DEVELOPMENT OF DESIGN CRITERIA FOR THE PREVENTION OF SLOPE FAILURES. EXECUTIVE SUMMARY

A total of 242 embankments were examined along a 122-mile transect of I-10 and I-20 highways in Louisiana. A total of 99 slope failures had occurred 8-15 years after construction (mean volume = 15,105 cu ft). Most of the failures occurred on slopes greater than 16 deg. Over 70% of the failures were found in modern alluvium parent material as compared to loess, sandy alluvium and Prairie Terrace alluvium. It is believed that the high amount of smectite in these soils created most of the failures when the slope moisture content rose. A predictive model for the first 15 years after construction was developed. A high-rise slope has an 85-90% chance of failure and is constructed of soil with: 47% clay content, a plasticity index (PI) 29%, a liquid limit (LL) 54%, and net smectite 33%. Low-risk slopes have a chance of less than 5% of failure and are constructed of soils with: 32% clay, 16% PI, 36% LL, and net smectite 18%. Determination of the risk category can be done easily in the laboratory using Atterberg limits. Control of slope stability depends upon control of expansive clays in the high- and intermediate-risk slope soils. It is recommended to lime stabilize these soils or use a new slope design. A map of the distribution of these soils in Louisiana is included. Four different design nomographs based on a stability model of the slopes is presented for soils in the high- and intermediate-risk categories. Depending upon the availability of space and economy, the designs include constant slope configuration, broken-back design, and soil-stabilized layers below the above two.

• Corporate Authors:

  Louisiana Tech University, Ruston

  Department of Petroleum Engineering and Geosciences
  Ruston, LA  United States  71272

  Louisiana Transportation Research Center

  4101 Gourrier Avenue
  Baton Rouge, LA  United States  70808

  Federal Highway Administration

  1200 New Jersey Avenue, SE
  Washington, DC  United States  20590
• Authors:
  • Burns, S F
  • Hadley, W O
  • Mutchler, J W
  • Smith, S M
  • Siddiqui, A
  • Hernandez, M
• Publication Date: 1990-3

Language

• English

Media Info

• Pagination: 18 p.

Subject/Index Terms

• TRT Terms: Alluvium; Atterberg limits; Calcium oxide; Clay; Clay minerals; Design; Embankments; Expansive clays; Hazards; Liquid limits; Maps; Moisture content; Nomographs; Plasticity index; Prevention; Risk assessment; Slope failure; Slope stability; Soil stabilization
• Uncontrolled Terms: Design criteria
• Geographic Terms: Louisiana
• Old TRIS Terms: Smectite
• Subject Areas: Design; Geotechnology; Highways; Safety and Human Factors; Security and Emergencies; I42: Soil Mechanics;

Filing Info

• Accession Number: 00625090
• Record Type: Publication
• Source Agency: Federal Highway Administration
• Report/Paper Numbers: FHWA/LA-88/210
• Contract Numbers: Study No. LA HPR 86-2GT(B)
• Files: TRIS, USDOT
• Created Date: Oct 15 1993 12:00AM