THE COLLAPSE OF DIAPHRAGM WALLS RETAINING CLAY

Five centrifugal model tests are reported which illustrate aspects of the collapse of stiff cantilever retaining walls embedded in overconsolidated clay. the drainage of a heavy fluid in flight was used to simulate the effects of excavation, following the establishment of a high initial groundwater level. Two modes of collapse were observed with unpropped walls. The temporary stability of walls with small penetration was interrupted by the hydraulic action of a water-filled crack opening on the retained side of the wall. The long-term rotational failure of walls of deeper penetration was also observed, involving distributed strains in 'active' and 'passive' zones which could lead ultimately to sliding on shear rupture surfaces. An analysis was developed based on admissible stress fields, with active and passive zones switching about a pivot point, so that the uproppped wall could satisfy the conditions of both moment and force equilibrium. A back analysis of the two sudden failures using an undrained strength based on the overconsolidation ratio was successful in matching the critical penetration ratio and pivot position observed in the tests. A drained analysis using phi derived from triaxial and plane strain tests was equally successful in comparison with the data of long-term failure. A similar stress analysis for a wall propped at the top was shown to be conservative. This was thought to be due to the kinematic restraint of the prop which produced a rupture surface on the active side which was much steeper than those observed before. A back analysis of the observed failure mechanism generated a credible value of mobilized soil friction close to the peak observed in soil tests. This value also gave a consistent match for the bending moments and propping force measured in the test. Care must be taken to account for the possible effects of progressive failure. Critical state soil angles, with fully mobilized wall friction, can be anticipated to relate to the gross long-term deformation of walls. Loss of retained height and heave in the excavation lead eventually to self-stabililzation.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/00168505
• Corporate Authors:

  Institution of Civil Engineers

  One Great George Street, Westminster
  London,   United Kingdom  SW1P 3AA
• Publication Date: 1987-9

Media Info

• Features: Appendices; Figures; References;
• Pagination: p. 335-353
• Serial:
  • GEOTECHNIQUE
  • Volume: 37
  • Issue Number: 3
  • Publisher: Thomas Telford Limited
  • ISSN: 0016-8505

Subject/Index Terms

• TRT Terms: Bending moments; Clay; Collapse; Diaphragm walls; Excavations; Failure; Groundwater; Mathematical models; Overconsolidation; Pendulum tests; Retaining walls; Structural analysis; Structural design; Water table
• Uncontrolled Terms: Models
• Old TRIS Terms: Groundwater level; Overconsolidated clay
• Subject Areas: Geotechnology; Highways; Hydraulics and Hydrology; I42: Soil Mechanics;

Filing Info

• Accession Number: 00475050
• Record Type: Publication
• Files: TRIS
• Created Date: Oct 31 1987 12:00AM