1 / 37

Soil compaction in three steps...

amber
Download Presentation

Soil compaction in three steps...

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. 4a. Mechanical stresses during wheel traffic Thomas Keller1,2, Mathieu Lamandé3, Matthias Stettler4 and Per Schjønning31Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; E-mail: thomas.keller@art.admin.ch2Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE-75007 Uppsala, Sweden3Department of Agroecology, Aarhus University, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark 4Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen, Switzerland

  2. Contacttyre/track-soil = Upper model boundarycondition: • Contactarea • Stress distribution • Stress propagation • Stress-strain (voidratio) relationship & Mechanicalsoilstrength • Stress > Strength Compaction • Stress < Strength Elasticdeformation Soil compaction in three steps...

  3. Stress propagation in soil Kolloquium FB31 | Bodenverdichtung

  4. Modelling stress propagation • Finite element modelling (FEM) • Continuum mechanics • Elasto-plastic stress-strain relationships (e.g. Modified Cam Clay) • Can account for stress-dependent material properties • Limitations: • Description of tyre-soil contact • Parameterization • (e.g. Richards & Peth 2009, Soil & Tillage Research 102) • Analytical solutions • Simple and robust • 3-Dimensional • Limitations: • Elastic theory • (e.g. Keller & Lamandé 2010, Soil & Tillage Research 111)

  5. Modelling stress propagation • Finite element modelling (FEM) • Continuum mechanics • Elasto-plastic stress-strain relationships (e.g. Modified Cam Clay) • Can account for stress-dependent material properties • Limitations: • Description of tyre-soil contact • Parameterization • (e.g. Richards & Peth 2009, Soil & Tillage Research 102) Suitableforeasily-applicabledecisionsupporttools  Approach in Terranimo® • Analytical solutions • Simple and robust • 3-Dimensional • Limitations: • Elastic theory • (e.g. Keller & Lamandé 2010, Soil & Tillage Research 111)

  6. Stress propagation: pointload P Forelastic material (Boussinesq, 1885): y x r Ѳ σr z Boussinesq J (1885) Application des Potentiels à l’étude de l’équilibre et du Mouvement des SolidesÉlastiques. Gauthier-Villars, Paris, 30 pp.

  7. Stress propagation: pointload Soil is not fullyelastic… Therefore (Fröhlich, 1934): P y x ν = „concentrationfactor“ (empiricalfactor) r Ѳ σr z FröhlichOK (1934) DruckverteilungimBaugrunde. Springer Verlag, Wien, 178 pp.

  8. Stress propagation: Söhne‘ssummationprocedure Pi zi σz Söhne W (1953) Druckverteilung im Boden und Bodenverformung unter Schlepperreifen. Grundlagen der Landtechnik 5, 49-63.

  9. ν = Concentrationfactor Stress propagation in soil (Boussinesq, 1884; Fröhlich, 1934; Söhne, 1953) Söhne W (1953) Grundlagen der Landtechnik 5, 49-63. Boussinesq J (1885) Application des Potentiels à l’étude de l’équilibre et du Mouvement des Solides Élastiques. Gauthier-Villars, Paris, 30 pp. Fröhlich OK (1934) Druckverteilung im Baugrunde. Springer Verlag, Wien, 178 pp. Söhne W (1953) Druckverteilung im Boden und Bodenverformung unter Schlepperreifen. Grundlagen der Landtechnik 5, 49-63.

  10. Stress distribution at the tyre-soil contact affects stress propagation Simulated, using measured stress distribution Simulated, using uniform stress distribution Measured stress

  11. Stress distribution at the tyre-soil contact affects stress propagation ? But…

  12. Idea… Easily-available tyre/loading properties (e.g., tyre dimensions, tyre inflation pressure, wheel load) and information on soil condition/consistency ? Model Stress distribution

  13. Measuring stress distributionatthetyre-soilinterface 2 1 3 4 Photos: Per Schjønning

  14. Upper model boundarycondition: Model „FRIDA“ Tyre: 800/50 R34; Wheel load: 6000 kg Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Contact area Stress distribution Measured Modelled Keller T (2005) A model for prediction of the contact area and the distribution of vertical stress below agricultural tyres from readily-available tyre parameters. Biosystems Engineering 92, 85-96. Schjønning P, Lamandé M, Tøgersen FA, Arvidsson J & Keller T (2008) Modelling effectsoftyreinflationpressure on the stress distributionnearthesoil-tyreinterface. Biosystems Engineering 99, 119-133.

  15. Predicting stress insoil Simulated, using measured stress distribution Simulated, using FRDIA generated stress distribution Simulated, using uniform stress distribution Measured stress

  16. Contacttyre/track-soil = Upper model boundarycondition: • Contactarea • Stress distribution • Stress propagation • Stress-strain (voidratio) relationship & Mechanicalsoilstrength • Stress > Strength Compaction • Stress < Strength Elasticdeformation Soil compaction in three steps...

  17. 6a. Stress transmissionThomas Keller1,2, Mathieu Lamandé3, Matthias Stettler4 and Per Schjønning31Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; E-mail: thomas.keller@art.admin.ch2Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE-75007 Uppsala, Sweden3Department of Agroecology, Aarhus University, Research Centre Foulum, P.O. Box 50, DK-8830 Tjele, Denmark 4Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen, Switzerland

  18. Stress propagation in soil: Simulation vs. measurements (typicalresult) Possible reasons (Keller & Lamandé, 2010): Upper model boundary condition is wrong Model for stress propagation is inappropriate Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111, 54-64.

  19. Stress propagation in soil: Simulation vs. measurements (typicalresult) FRIDA Possible reasons (Keller & Lamandé, 2010): Upper model boundary condition is wrong Model for stress propagation is inappropriate Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111, 54-64. We know that we are within  10% (Lamandé et al., unpublished) This cannot account for the discrepancies (Keller & Lamandé, 2010)

  20. Stress propagation in soil: Simulation vs. measurements (typicalresult) Possible reasons (Keller & Lamandé, 2010): Upper model boundary condition is wrong Model for stress propagation is inappropriate Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111, 54-64.

  21. Stress propagation in soil: towards a 2-layer approach A pragmatic model wouldbe: Tilledlayer(e.g. 0-0.25 m depth): no stress attenuation Subsoil: accordingto Söhne (1953)

  22. Estimation of theconcentrationfactor: Approach (i) Field measure-ments of σz Simulations of σz with different valuesforconcentrationfactor (ν). Comparison: When (atwhichν)doesthesimulatedσz fit bestthemeasuredσz (lowest RMSE)?

  23. Estimation of theconcentrationfactor: Approach (ii) ν = f (soil properties, loading) Linear regressionmodel (whichsoilproperties and loadingcharacteristicsdescribebesttheoptimizedν?)

  24. Estimation of theconcentrationfactor: Resultsfrom a preliminarystudy Regression fordatafromwheelingexperiments on sevensoils (12 -61% clay) yields: σpc [kPa] Sand [%] σpc↑  ν ↓ Sand ↑ ν ↑ Keller T, Stettler M, Arvidsson J, Lamandé M, Schjønning P, Berli M & Rydberg T (2009) Stress propagation in arablesoil: determination and estimation of theconcentrationfactor. Proc. 18th Conf. ISTRO, Izmir, Turkey, 15-19 June 2009.

  25. 6c. WP1: Soil mechanical models and pedotransfer functions

  26. Model approach • Estimation of model parameters

  27. 1. Modelling approach: a) upper model boundarycondition (i) Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Contact area Stress distribution ?

  28. 1. Modelling approach: a) upper model boundary condition (ii) Easily-available tyre/loading properties (e.g., tyre dimensions, tyre inflation pressure, wheel load) and information on soil condition/consistency Empiricalmodels foreach of the FRIDA model paremeters Upper model boundary condition e.g.:  = a Ptyre + b PWheelLoad Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Parameters: Contact area: l and w, n, Stress distribution: α and 

  29. 1. Modelling approach: b) stress propagation A new semi-empirical model: Tilledlayer(e.g. 0-0.25 m depth): no stress attenuation Subsoil: accordingto Söhne (1953) Compare, and selectthebestperforming model… „Classical“ one-layer model (Söhne, 1953)

  30. 1. Modelling approach: c) compressivesoilstrength Pragmatic model: CS = kx PCS where: CS = compressivestrength (kPa) PCS = precompression stress (kPa) k = empiricalfactor (-), k = 0..1

  31. Model approach • Estimation of model parameters

  32. 2. Estimation of model parameters: a) upper model boundarycondition (ii) • Data available: • Measurements from Sweden (Keller, 2005) • Measurements from Denmark (Schjønning et al., 2006, 2008; Lamandé & Schjønning, 2008; Lamandé & Schjønning, in press) • Unpublished data from Denmark [designed to study impacts of soil consistency] (Schjønning et al., unpublished) • Work to be done: • Compile data (mostly done) • Find appropriate parameter (property) to characterize soil consistency • Develop „tyre-transfer functions“ for estimation of FRIDA model parameters

  33. 2. Estimation of model parameters: b) stress propagation • Data available: • Measurements from Sweden, using load cells (Keller, 2004; Keller & Arvidsson 2004, 2006; Keller & Lamandé, 2010) • Measurements from Denmark, using load cells (Lamandé & Schjønning, 2007; Lamandé & Schjønning 1-3, in press; Keller & Lamandé, 2010) • Measurements from Switzerland, using Bolling probes (Anken et al., 1993; Zihlmann et al., 1995, Diserens & Anken, 1995; Anken et al., 2000; Gysi et al., 2001; van der Veer, 2004; Schäffer et al., 2007) • Work to be done: • Compile data (mostly done) • Correct stress readings (Berli et al., 2006; Lamandé et al., unpublished) • Simulate stress and compare with measurements  (i) best model (“2-layer” vs. “classical”), and (ii) concentration factor • Develop „pedo-transfer functions“ for estimation of the concentration factor

  34. 2. Estimation of model parameters: c) soilstrength • Data available: • Uniaxial compression from Switzerland (Weisskopf et al., unpublished), Sweden (Keller & Arvidsson, 2007; Keller et al., in press; Keller, unpublished) and Denmark (Schjønning, 1996; Schjønning & Lamandé, unpublished) • In situ stress-strain data from Sweden (Keller, 2004; Keller & Arvidsson 2004, 2006; Keller & Lamandé, 2010) and Denmark (Lamandé & Schjønning, 2007; Lamandé & Schjønning 1-3, in press; Keller & Lamandé, 2010) • Work to be done: • Merge and harmonize data (mostly done) • Agree on a proper method to obtain precompression stress • Develop „pedo-transfer functions“ for estimation of precompression stress • Find the empirical factor “k” that relates soil strength to precompression stress

  35. 7c. Structure of soil and weather data bases, Switzerland Thomas Keller1,2 and Matthias Stettler31Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; E-mail: thomas.keller@art.admin.ch2Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE-75007 Uppsala, Sweden3Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen, Switzerland

  36. A. Soil data • A national soildatabasedoes not exist…, but is in progress (however, tobeexpected after the end of PredICTor)… • Somecounties („Kantons“) do have GIS-basedsoilmaps ( perhapsthiscouldbeusedas a pilotstudyarea) • Best soilmap of Switzerland: „Soil suitabilitymap“ (suitabilitywithregardtoagriculturalproduction; „Bodeneignungskarte“) 1:200‘000 • Somecounties do havesoilmaps 1:5‘000 to 1:25‘000 • Problem: existingsoildata and mapsareratherdescriptive (e.g. noexactvalues of claycontent but onlyclasses)

  37. B. Meteorologicaldata • Agroscope ART hasdirectaccesstoabout 60 official (MeteoSwitzerland) weatherstations of Switzerland (hereby, datafromtheseweatherstationsaremirroredto a database on an instituteservereverynight) • The dataincludesprognosis of thecomingtwodays • Data fromthedatabasecouldbeaccessedfromTerranimo® (discussed and confirmedat a meeting in Zürich last October)

More Related