SLIP CONFIRMS CUTTING THEORY

The recent slipping of an embankment on the North circular road appears to confirm the theory put forward by Professor Stempton in 1977 that if a slope is unstable, failure occurs many years after construction. Back analysis of typical long term slips has shown that the strength of the clay at failure corresponds closely to the clay's fully softened condition or its fissure strength. The failure of the 1:2 sloped cutting, it having been designed on the basis of knowledge current in the 1960s, casts doubts on the stability of the country's many hundreds of similar slopes designed in the 1960s and early 1970s. Pore pressure equilibrium is slow and these pressures are negative in overconsolidated material just after construction because the clay is in the process of heaving, its overburden having been removed. The significance of the residual factor in the likely stability is examined. This factor is a function of peak strength, residual strength and average shear strength. A value of unity indicates an infinite stability whereas the value of 0.5 found at the site suggests a failure within the eight years experienced. Curing a landslip is usually in one of six ways: lime addition, geogrid reinforcement, gabion wall, tyre wall, ground anchors or rock ribs. Geogrid is being used at the site to maintain the steep slope at the cutting. (TRRL)

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03077683
• Corporate Authors:

  Institution of Civil Engineers

  One Great George Street, Westminster
  London,   United Kingdom  SW1P 3AA
• Authors:
  • Dadson, J
• Publication Date: 1986-1-9

Media Info

• Features: Photos;
• Pagination: p. 20-21
• Serial:
  • NEW CIVIL ENGINEER
  • Issue Number: 672
  • Publisher: EMAP CONSTRUCT LIMITED
  • ISSN: 0307-7683

Subject/Index Terms

• TRT Terms: Clay; Embankments; Failure; Geogrids; Geotextiles; Landslides; Pore pressure; Residual strength; Shear strength; Slope stability; Stability (Mechanics); Strength of materials
• Uncontrolled Terms: Slippage
• Old TRIS Terms: Embankment stability; Peak strength
• ITRD Terms: 4177: Clay; 5791: Consolidation (soil); 2812: Cutting (earthworks); 2801: Embankment; 5520: Failure; 4029: Landslide; 9069: Residual; 5531: Shear; 5783: Slope stability; 5544: Strength (mater); 5414: Time; 8119: United Kingdom
• Subject Areas: Geotechnology; Highways;

Filing Info

• Accession Number: 00471161
• Record Type: Publication
• Source Agency: Transport Research Laboratory
• Files: ITRD, TRIS
• Created Date: May 31 1987 12:00AM