UNDRAINED STABILITY OF BRACED EXCAVATIONS IN CLAY

Short-term undrained stability often controls design of braced excavations in soft clays. This paper summarizes the formulation of numerical limit analyses that compute rigorous upper and lower bounds on the exact stability number and include anisotropic yielding, typical of K-sub-0 consolidated clays and bending failure of the wall. Calculations for braced cuts bound the actual failure conditions within 5%, and highlight limitations of existing basal stability equations. The analyses clarify how wall embedment and bending capacity improve the stability of well braced excavations. Careful selection of mobilized strengths at shear strains in the range 0.6--1.0% are necessary to match the predictions of anisotropic limit analyses with nonlinear finite-element predictions of failure for the embedded walls. Two example applications from recent projects in Boston highlight the practicality of the numerical limit analyses for modeling realistic soil profiles and lateral earth support systems, but also focus attention on the need for careful selection of undrained strength parameters. Credible estimates of stability have also been obtained in reanalyzing a series of case studies reported in literature using isotropic strength parameters derived from field vane or laboratory simple shear tests.

• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/oclc/3519342
• Corporate Authors:

  American Society of Civil Engineers

  1801 Alexander Bell Drive
  Reston, VA  United States  20191-4400
• Authors:
  • Ukritchon, B
  • Whittle, A J
  • Sloan, S W
• Publication Date: 2003-8

Language

• English

Media Info

• Features: Figures; References; Tables;
• Pagination: p. 738-755
• Serial:
  • Journal of Geotechnical and Geoenvironmental Engineering
  • Volume: 129
  • Issue Number: 8
  • Publisher: American Society of Civil Engineers
  • ISSN: 1090-0241
  • Serial URL: http://ojps.aip.org/gto

Subject/Index Terms

• TRT Terms: Anisotropy (Physics); Clay soils; Excavation and tunneling; Finite element method; Foundation engineering; Foundation soils; Geotechnical engineering; Soft clays; Soil mechanics; Soil stabilization; Undrained strength
• Uncontrolled Terms: Braced excavations
• Subject Areas: Geotechnology; Highways; I42: Soil Mechanics;

Filing Info

• Accession Number: 00961675
• Record Type: Publication
• Files: TRIS
• Created Date: Aug 12 2003 12:00AM