In the closure of the discussion of this paper, the authors comment on the use of the burette method for determining values of earth pressure, Ko. Comparison of tests using both the burette method and the interpolation method using materials with larger size particles (particles larger than 0.1 mm), showed that the errors in the strains were significant and influenced the test procedure in the burette method as it is a strain controlled test. Errors due to membrane penetration may have affected the results of tests on materials with particle size range of 1.2 mm-7.9 mm. Regarding the choice of two values of constant stress ratios required for the interpolation method for a material with an unknown value of Ko, it is suggested that a preliminary Ko test be conducted using the burette method from which an approximate value of Ko can be obtained. Two tests with constant stress ratio in the vicinity of 1/Ko can thus be performed and the measured stains corrected. The correct value for Ko is then determined by interpolation. Observations are made regarding the relationship of Ko to phi. The higher values of Ko for feldspar is due to crushing at the points of contact caused by the very angular shape of the feldspar particles thus increasing the overall sliding component. For a strong material (where the elastic decrease in diameter is small), a low value of constant stress ratio (which produces a small sliding increase in diameter) is required to maintain zero lateral deformation. Thus, as the modulus of elasticity of the particles mineral increases, Ko increases.

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  • Accession Number: 00080834
  • Record Type: Publication
  • Report/Paper Numbers: Proc. Paper 10973
  • Files: TRIS
  • Created Date: Mar 6 1975 12:00AM