Soil Stress Measurement: Part I. Transducer in a Uniform Stress Field

Transmission of vertical stress in a real soil profile. Part I: Site description, evaluation of the Söhne model, and the effect of topsoil tillage

“…Using a finite element model, Kirby (1999) showed that stress measurements in soil might be overestimated due to the difference of stiffness between the soil and the transducers and the geometry of the transducers. We did not measure statistically significant differences in soil strength between the three depths of stress measurements (0.35, 0.6 and 0.9 m depths; Table 3).…”

“…However, the quality of the fit was different for the three depths (Table 6). Our stress transducers were designed to minimize other problems in stress measurements mentioned by Kirby (1999) (e.g. we used cylindrical transducer housings; consult Lamandé et al (2006Lamandé et al ( , 2007 for details).…”

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

“…1 The predicted vertical and lateral stresses were 1)366 and 0)338 kPa with the ratio being 0)244. However, the predicted stresses for a stress state transducer in the varying stress "eld beneath the circular load were 1)272 and 0)218 kPa with the ratio being 0)171.…”

Subsoil compaction due to wheel traffic.

“…According to Koolen et al (1992), the shear effect vanishes relatively rapidly with depth. However, Kirby (1989) concluded from a model evaluation that shear damage may extend to a depth of 1.5 to 2 times the tyre width in a soil profile of uniform strength. Even though the shear effect may vanish rapidly, it can damage the subsoil markedly, especially during ploughing, owing to furrow wheel slipping.…”

“…Hard-pan tends to act like an elastic bridge, spreading the load over a wider area by reducing the concentration factor (Dexter et al 1988). Thus, finite-element models are more often used, to take into account the heterogeneity of a soil profile (Kirby 1999). Likewise, the analytical solution described above is based on static stress.…”