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Mechanical Stresses in Soils Assessed from Bulk‐Density and Penetration‐Resistance Data Sets
Author(s) -
Horn R.,
Hartge K. H.,
Bachmann J.,
Kirkham M. B.
Publication year - 2007
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2006.0044
Subject(s) - soil water , dimensionless quantity , bulk density , penetration (warfare) , soil science , hydrostatic equilibrium , geotechnical engineering , topsoil , materials science , geology , mathematics , mechanics , physics , operations research , quantum mechanics
Measurement of soil strength with sophisticated parameters is tedious and expensive. Therefore, we developed two straightforward methods to determine this parameter down to about 80 cm, based on the classical measurements of bulk density and penetration resistance as a function of depth. They were applied to three profiles of arable Luvisols, all developed from glacial till. For each method, a procedure was worked out that allows expression of the results in terms of a normal (NC) or precompacted (PC) state. We defined the NC state as that observed in packing characteristics of virgin soils like forests and meadows, and the PC state as the packing characteristics that exist in the topsoil of agricultural soils and intensely grazed areas. Bulk density data were used to examine the packing characteristics and overburden pressures with the assumption that the horizon was in a NC state below 80 cm. For penetration resistance, we assumed a linear increase in penetration resistance with depth to represent the hydrostatic stress distribution in the NC state and deviations of measured values from this line as the PC state. The upper approximately 60 cm of all three soils were compacted, which is proofed both for the penetration resistance and for the bulk density data. For both approaches, the dimensionless coefficient of “stresses at rest,” K 0 , was calculated following the line of thought used in engineering soil mechanics ( K 0 = σ x /σ z , where σ x and σ z are the horizontal and vertical stresses, respectively). The K 0 values are highest in the precompacted soil horizons and decrease with depth.