EVALUATION OF STRESS CELL PERFORMANCE

The discussers present results of an independent study similar to that presented by the authors, and offer some additional conclusions. The nature and compactness of the bedding soil sorrounding earth pressure cells (in instrumenting test embankments) are very important parameters. In an effort to understand the exact influence of the degree of compactness of the bedding soil, a finite element study using a non-linear stress-dependent elastic model was performed. The bedding soil modulus was varied to represent the following conditions: undercompaction; overcompaction; and ideal compaction. The typical results of the finite element analysis are given, and the combined effects of the arching and of peripheral stress concentrations are tabulated as the ratios of the measured actual stresses at the center and periphery of the cell. The percentages of overregistration or underregistration in the different cases analyzed are also presented. The results indicate that arching strongly affects the vertical stress distribution, and that in all cases stress concentration occurs at the periphery of the cell due to the abrupt change in compliance between soil and metal. It is concluded that total stresses, measured in a soil mass, represent the actual stresses within a few percent only if the following conditions are fulfilled: (1) thickness to diameter ratio of the cell is less than 0.1; (2) stress sensitive area less than one-half the total area of the cell. If necessary, the cell should be mounted in a steel plate of greater area; (3) flexiblity factor of the cell less than 2; and (4) bedding material around the cell compacted to the same density and stiffness as the soil mass.

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Filing Info

  • Accession Number: 00099107
  • Record Type: Publication
  • Report/Paper Numbers: ASCE #11398 Proceeding
  • Files: TRIS
  • Created Date: Oct 18 1975 12:00AM