PHYSICS OF SWELLING AND CRACKING SOILS

The environment of a layer of swelling, unsaturated soil is described by two quantities: The most direct choices are an overburden pressure P and a tensiometer pressure pw. Their difference, P - pw is the swelling pressure, Ps. The water volume fraction theta of rigid unsaturated soils depends only on pw. The porosity f of saturated swelling soils depends only on ps. Thus, it is convenient to regard the characteristics of general unsaturated swelling soils as dependent on pw and Ps. SImplifying to monotonic histories, the characteristics can be represented by two functions, theta (Pw, Ps) and f (pw,Ps). Introducing Darcy's law and the continuity condition leads to solutions for steady or unsteady profiles subject to a "unidirectional" rheological constraint (zero horizontal strain). The advantage of this approach is that all the quantities employed can be measured physically and in situ. This contrasts to the use by Philip, Bolt, and others of an "overburden potential" described by an integral over a series of states of the properties of the soil. The motivation for this simpler approach was an interest in the nature of their reversible or hysteretic characteristics of swelling soils. Experimentally, the advantage of a system based on directly measureable quantities is obvious. Surface cracking of swelling soils is discussed in the same terms but under a different (isotropic) rheological constraint.

  • Corporate Authors:

    Academic Press Incorporated

    111 Fifth Avenue
    New York, NY  USA  10003
  • Authors:
    • Miller, E E
  • Publication Date: 1975-9

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  • Accession Number: 00148868
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Mar 30 2002 12:00AM