Soil Stress Measurement. Part 2: Transducer beneath a Circular Loaded Area

✍ Scribed by J.M. Kirby

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 204 KB
• Volume: 73
• Category: Article
• ISSN: 0021-8634
• DOI: 10.1006/jaer.1998.0400

✦ Synopsis

In this paper the "nite element method was used to examine the stresses predicted around transducers beneath the centre of a circular loaded area analogous to a tyre. Vertical transducers and stress state transducers, disturbed zones (both weaker and stronger), stress gradients around the transducer, depth, tyre size and the presence of hardpans are all considered.

The stresses can be over-or underestimated depending on conditions, with disturbed zones of soil, degree of elastic as opposed to elastoplastic behaviour, depth in the soil, tyre size and hardpans all a!ecting the results. When there was no disturbed zone, the vertical transducer always yielded an estimate of vertical stress closer to the expected value than did a stress state transducer. In the varying stress "elds considered here, the lateral stress was often underestimated by the stress state transducer and was sometimes even negative. This did not occur in similar uniform stress "elds but arose because of the stress gradients in the vicinity of the transducer. Reports in the literature of negative stresses measured by stress state transducers might therefore be questioned and certainly should be analysed thoroughly.

The mean stress and deviator stress always di!ered from those expected in the absence of transducers with generally either one or both being overestimated by a factor of about two. The absolute magnitudes of the mean stress and deviator stress are to be viewed with caution, but the trends with tyre size and hardpan strength were qualitatively as expected. Therefore, it appears reasonable to use transducers to study relative e!ects but inferences drawn from absolute values should be treated with caution and subject to detailed analysis of the sort described here.