Daniel A. Leavell

Relationship Between Tensile and Compressive Strengths of Compacted Soils

A direct-pull tension test was developed to study the behavior of compacted soils in total stress tension. A comprehensive series of tension and unconsolidated undrained compression tests was performed on Vicksburg silty clay; the data from these tests were supplemented with published data. Analysis of the data was based on relating the tensile strength parameter of the Griffith-Brace theory for brittle fracture to the suction-derived cohesion term of the Fredlund-Morgenstern failure law for partially saturated soils. Application of the analysis was demonstrated by relating tensile and compressive strengths to water content and void ratio.

A Biaxial Consolidation Test for Anisotropic Soils

A biaxial flow consolidation test was developed to determine the axial and radial permeabilities, k a and k r , respectively, of a transversely isotropic specimen. The test enables the additional information needed to determine the ratio of permeabilities, k a /k r , to be obtained by independently measuring the flow from the specimen ends and circumference during consolidation. By comparing the ratio of flows from the specimen ends and circumference to the theoretical relationship, the ratio of permeabilities can be determined. The radial permeability, k r , is determined from the total time rate of consolidation. Comparisons between various methods of permeability measurement and the proposed test are shown to be good. From the theoretical development, it was found that anisotropy in stiffness can have an important influence on test results. A method is presented for determining relevant stiffness parameters by combining the strain measured during consolidation and pore-pressure response.