Topsoil shear strength – Measurements and predictions

• Soil shear strength, τ, was measured in intact topsoil at six matric potentials. The preload suction stress (PSS) estimated from water saturation and suction. Normal load, PSS, density, clay organic matter explained >90 % of variation τ. model predicted well τ for two independent data sets. the trend also subsoil Distortion soil stresses during field traffic may be even more damaging to functions than compression related isotropic stresses. A torsional test applied undisturbed samples drained either potentials (range -30 -300 hPa) tested normal loads, NL 30–180 kPa)(Series A). (SOM) content ranged 0.038−0.157 0.021−0.033 kg −1 , respectively. Bulk density (BD) varied 1.19 1.71 g cm -3 . stress, calculated as product pore hPa. PSS 17 234 Data sets with contrasting texture (Series B: loess soil) or management C: long term fertilization) but same methodology were included validation prediction equations established Series soils. Multiple regression revealed that cohesion taken intercept a linear correlated positively BD SOM, while internal friction slope poorly by properties. combining tests clay, SOM accounted 90 is suggested pedotransfer function (ptf) given loading conditions. B C Also similarly textured reasonably ptf. In accordance theory, seems key driver mechanical strength. More measurements strength further studies effect are encouraged.