THE ROLE OF FILL STRENGTH IN THE STABILITY OF EMBANKMENTS ON SOFT CLAY FOUNDATIONS

Results from nonlinear finite element analyses show that when an embankment is stronger and stiffer than its foundation, the percentage of strength mobilized in the embankment is smaller than in the foundation. These studies showed that the "equal strain" concept of progressive failure is invalid; the strains in a stiff embankment are inevitably smaller than those in the foundation. The more severe the stress-strain incompatibility between the embankment and its foundation, the smaller is the portion of the embankment strength which can be mobilized before failure begins in the foundation. These studies were used as a basis for a simple method to allow for progressive failure effects in analyses of stability. Finite element analyses indicate that tension develops in embankments due to a tendency for clay to be squeezed from beneath the center of the embankment out outward the edges, and that cracks tend to propagate from the bottom to the top of the embankment. An experimental study, using flexure tests on beams of compacted soil, showed that once a crack developed, it continued to propagate and the beams eventually collapsed under their own weight. From the results of a parameter study on the effects of several factors affecting the development of tension in embankments, an empirical equation was developed which can be used to estimate the height at which an embankment will crack. The results of the studies of progressive failure and cracking were employed in developing a rotational method for estimating whether cracks will develop in an ambank,ent, and for determining what portions of the embankment and foundation strengths should be used in evaluation of the stability. A preliminary study was made to investigate the effectiveness of steel reinforcing in preventing cracking of cohesive fills on soft foundations. The results indicate that reinforcing can be very effective, and that further studies of reinforcing would be desirable. /Author/

  • Corporate Authors:

    University of California, Berkeley

    College of Engineering
    Berkeley, CA  USA  94720
  • Authors:
    • Chirapunta, S
    • Duncan, J M
  • Publication Date: 1976-6

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 225 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00139253
  • Record Type: Publication
  • Report/Paper Numbers: TE-75-3 Final Rpt.
  • Contract Numbers: DACW39-68-C-0078
  • Files: TRIS
  • Created Date: Sep 4 1976 12:00AM