Consolidation of soft layers by finite strain analysis
Cargill, Kenneth W.
Miscellaneous paperAbstract: The general theory of one-dimensional finite strain consolidation is developed in terms of the void ratio and time for a moving coordinate system and a material or reduced coordinate system which is time independent. The governing equation is based on fluid continuity and material equilibrium and is totally independent of any restrictions on the form of the void ratio-effective stress and void ratio-permeability relationships. Boundary and initial conditions necessary for for a normally consolidated layer and a dredged fill layer are illustrated. Boundary conditions for the free-draining, impermeable, and semipermeable interfaces are derived. A solution of the nonlinear governing equation is derived through the use of an explicit finite difference scheme which preserves the nonlinearity by constantly updating coefficient terms. Solution includes appropriate boundary and initial conditions for any normally consolidated or dredged fill layer. Method of settlement, soil stress, and pore pressure calculation is also given. Conditions necessary for a consistent, stable, and convergent solution are derived in terms of governing equation coefficients. Equation solution requires laboratory-determined void ratio-effective stress and void ratio-permeability relationships in the form of point values. The determination of these relationships from oedometer testing is discussed. Parameters required for handling semipermeable boundaries are also discussed. Typical problems involving consolidation of soft layers are solved through use of the computer program CSLFS (Consolidation of Soft Layers, Finite Strain). The first problem involves deposition of multiple layers of dredged fill material on a compressible foundation. The second concerns a soft layer subjected to multiple surcharge loads as would occur through phased construction. A user's manual for the computer program CSLFS, a program listing, and sample problems are included as Appendixes. equation solution are discussed.
Geotechnical Laboratory (U.S.)Engineer Research and Development Center (U.S.)
Computer programs; CSLFS (Computer program); Difference equation, Nonlinear; Soil consolidation
Miscellaneous paper (U.S. Army Engineer Waterways Experiment Station) ; GL-82-3.
Approved for public release; distribution is unlimited.