Soil stress measurement: Part I. Transducer in a uniform stress field

In this paper, the finite element method is used to examine the stresses predicted around transducers in a uniform applied vertical stress field. Vertical transducers and stress state transducers, disturbed zones (both weaker and stronger) around the transducer and the influence of soil shear and compression properties are all considered. Very thin (1-2 mm) disturbed zones alter the stresses estimated using transducers. When the disturbed zone around the transducer is weaker than the undisturbed soil, both vertical and stress state transducers underestimate stresses. When there is no disturbed zone, or when the disturbed zone is stronger than the surrounding soil, the transducers overestimate the stresses except in wet, weak soil. In wet, weak soil the stresses may be close to hydrostatic and accurate estimates of the applied stresses in the soil might be obtained. In general, however, it would appear that the stress transducers are unlikely to yield accurate estimates of the applied stresses in a uniform stress field. Many factors influence the stresses estimated by soil stress transducers. There is no general means of correcting the results to infer the applied stresses in a uniform stress field, other than by a detailed analysis of the sort described here. Inferences drawn from absolute values should be treated with caution and subject to detailed analysis. (C) 1999 Silsoe Research Institute.