This study was undertaken to develop the theory for analyzing the consolidation of partly saturated clay soils, and subsequently to develop a practical procedure for performing finite element analyses of the behavior of dams during construction, during reservoir filling, and during the development of long-term seepage. The theory developed couples the effects of both stress and flow. It takes account of the varying permeability and compressibility of the pore fluid, and the nonlinear stress-strain behavior of the soil. A number of elastic-plastic, stress-strain relationships are reviewed with respect to their capabilities for modeling the stress-strain behavior of compacted clays. It is shown that if the Cam Clay Model is revised by introducing a cohesion intercept and a nonlinear curve, it can be used to model the stress-strain behavior of compacted clay quite accurately. This model provides an incremental stress-strain relationship which can be used for analyses of drained, undrained, and partly drained conditions. Available data are reviewed to show how the permeability of compacted clays varies with degree of saturation and void ratio, and an empirical relationship is developed which expresses the dependence of permeability on these factors for a wide variety of compacted clays. A concept of homogenized pore fluid is proposed to simulate the air-water mixture in the pores of partly saturated clays so that the three-phase partly saturated clay can be treated phenomenologically as a two-phase material. Compressibility of the homogenized pore fluid is then derived using Boyle's Law and Henry's Law and taking account of the effect of surface tension. Biot's theory of consolidation is reviewed, and a finite element formulation for the consolidation of saturated soils is derived. The computer program based on this formulation is verified by comparing results derived from the program with known solutions for several problems. The theory of consolidation for partly saturated soil is derived and a computer program is developed. To check the utility and effectiveness of the theory and the computer program developed, two examples of one-dimensional consolidation with compressible pore fluid and varying permeability are analyzed. Finite element analyses performed using this program are shown to agree well with closed-form solutions for the consolidation of both saturated and unsaturated soils. A finite element analysis is performed to study the stresses and movements in New Melones Dam, which is now under construction. The results of this analysis indicate that the behavior of the dam during consolidation is closely related to the stiffness and degree of saturation of the core. The results of this study indicate that the finite element procedure developed is a potentially useful tool. It seems likely that its greatest value in application will be in connection with interpretation of instrumentation studies for zoned earth and rockfill dams. /Author/

  • Availability:
  • Supplemental Notes:
    • Prepared for U.S. Army, Office of Chief of Engineers.
  • Corporate Authors:

    University of California, Berkeley

    College of Engineering
    Berkeley, CA  USA  94720
  • Authors:
    • Chang, C S
    • Duncan, J M
  • Publication Date: 1977-9

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 127 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00167840
  • Record Type: Publication
  • ISBN: TE 77-3
  • Report/Paper Numbers: Contract Rpt. S-77-4Final Rpt.
  • Contract Numbers: DACW39-74-C-0027
  • Files: TRIS
  • Created Date: Jan 13 1978 12:00AM