The first discusser of this paper comments on the author's overreliance on papers having limited geographic range, and to the limiting of the study to three principle clay minerals. The paper fails to recognize the microenvironment and the changes that environment undergoes during the life of the structure. The paper is a partial review of expansive soils. The data presented, although it may be valid, is not verified or evaluated. The second discusser questions the use of simple soil tests (shrinkage limit, linear shrinkage, free swell, plasticity, etc) to indicate the degree of expansion of a particular clay site. The discusser makes the observation that if 0.5 m of topsoil and possible silty clay exist above this clay and the climate of of the site is humid, then the degree of expansion or movement at this site would be considerably reduced. The depth of the seasonal movement also must be considered when deciding the significance of topsoil in reducing the movements of underying expansive soils. This argument is illustrated by the discusser's experience. The authors concept that a pier and beam foundation system is superior to a raft slab system in high movement soil is also disputed. Practical experience is quoted in support of this statement. A research program is currently in progress to study the design residential raft slabs on expansive clays. The failure of raft slabs may be possibly due to the fact that the British Research Advisory Board (BRAB) method used, does not consider the total differential movement at the particular site but rather arrives at a figure for the general region, based mainly on plasticity index and climatic factor.

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  • Accession Number: 00096254
  • Record Type: Publication
  • Report/Paper Numbers: Discussion
  • Files: TRIS
  • Created Date: Jul 15 1975 12:00AM