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Eidgenössisches Volkswirtschaftsdepartement EVD Forschungsanstalt Agroscope Reckenholz-Tänikon ART 4a. Mechanical stresses during wheel traffic Thomas.

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Presentation on theme: "Eidgenössisches Volkswirtschaftsdepartement EVD Forschungsanstalt Agroscope Reckenholz-Tänikon ART 4a. Mechanical stresses during wheel traffic Thomas."— Presentation transcript:

1 Eidgenössisches Volkswirtschaftsdepartement EVD Forschungsanstalt Agroscope Reckenholz-Tänikon ART 4a. Mechanical stresses during wheel traffic Thomas Keller 1,2, Mathieu Lamandé 3, Matthias Stettler 4 and Per Schjønning 3 1 Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; 2 Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE Uppsala, Sweden 3 Department of Agroecology, Aarhus University, Research Centre Foulum, P.O. Box 50, DK Tjele, Denmark 4 Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen,

2 2 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 1.Contact tyre/track-soil = Upper model boundary condition:  Contact area  Stress distribution 2.Stress propagation 3.Stress-strain (void ratio) relationship & Mechanical soil strength  Stress > Strength  Compaction  Stress < Strength  Elastic deformation Soil compaction in three steps...

3 3 Kolloquium FB31 | Bodenverdichtung Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Stress propagation in soil

4 4 Analytical solutions  Simple and robust  3-Dimensional  Limitations: Elastic theory (e.g. Keller & Lamandé 2010, Soil & Tillage Research 111) 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) Modelling stress propagation

5 5 Analytical solutions  Simple and robust  3-Dimensional  Limitations: Elastic theory (e.g. Keller & Lamandé 2010, Soil & Tillage Research 111) 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) Modelling stress propagation Suitable for easily- applicable decision support tools  Approach in Terranimo ®

6 6 Numerical methods… Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Finite elemente method (FEM) Discrete element method (DEM) From Jean-Yves Delenne (University of Montpellier, Frankreich)

7 7 x y z r Ѳ P σrσr For elastic material (Boussinesq, 1885): Stress propagation: point load Boussinesq J (1885) Application des Potentiels à l’étude de l’équilibre et du Mouvement des Solides Élastiques. Gauthier-Villars, Paris, 30 pp. Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

8 8 Soil is not fully elastic… Therefore (Fröhlich, 1934): x y z r Ѳ P σrσr ν = „concentration factor“ (empirical factor) Stress propagation: point load Fröhlich OK (1934) Druckverteilung im Baugrunde. Springer Verlag, Wien, 178 pp. Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

9 9 σzσz PiPi zizi Stress propagation: Söhne‘s summation procedure Söhne W (1953) Druckverteilung im Boden und Bodenverformung unter Schlepperreifen. Grundlagen der Landtechnik 5, Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

10 10 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART (Boussinesq, 1884; Fröhlich, 1934; Söhne, 1953) Stress propagation in soil 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, ν = Concentration factor Söhne W (1953) Grundlagen der Landtechnik 5,

11 11 Stress distribution at the tyre-soil contact affects stress propagation Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Simulated, using uniform stress distribution Measured stress Simulated, using measured stress distribution

12 12 Stress distribution at the tyre-soil contact affects stress propagation Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART ? But…

13 13 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Idea… ? Model Stress distribution Easily-available tyre/loading properties (e.g., tyre dimensions, tyre inflation pressure, wheel load) and information on soil condition/consistency

14 14 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Measuring stress distribution at the tyre- soil interface Photos: Per Schjønning

15 15 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Tyre: 800/50 R34; Wheel load: 6000 kg Upper model boundary condition: Model „FRIDA“ 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, Schjønning P, Lamandé M, Tøgersen FA, Arvidsson J & Keller T (2008) Modelling effects of tyre inflation pressure on the stress distribution near the soil-tyre interface. Biosystems Engineering 99, Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Contact area Stress distribution

16 16 Predicting stress in soil Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Simulated, using uniform stress distribution Measured stress Simulated, using FRDIA generated stress distribution Simulated, using measured stress distribution

17 17 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 1.Contact tyre/track-soil = Upper model boundary condition:  Contact area  Stress distribution 2.Stress propagation 3.Stress-strain (void ratio) relationship & Mechanical soil strength  Stress > Strength  Compaction  Stress < Strength  Elastic deformation Soil compaction in three steps...

18 Federal Department of Economic Affairs FDEA Agroscope Reckenholz-Tänikon Research Station ART 6a. Stress transmission Thomas Keller 1,2, Mathieu Lamandé 3, Matthias Stettler 4 and Per Schjønning 3 1 Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; 2 Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE Uppsala, Sweden 3 Department of Agroecology, Aarhus University, Research Centre Foulum, P.O. Box 50, DK Tjele, Denmark 4 Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen,

19 19 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Stress propagation in soil: Simulation vs. measurements (typical result) Possible reasons (Keller & Lamandé, 2010): (1)Upper model boundary condition is wrong (2)Model for stress propagation is inappropriate (3)Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111,

20 20 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Stress propagation in soil: Simulation vs. measurements (typical result) Possible reasons (Keller & Lamandé, 2010): (1)Upper model boundary condition is wrong (2)Model for stress propagation is inappropriate (3)Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111, FRIDA 1)We know that we are within  10% (Lamandé et al., unpublished) 2)This cannot account for the discrepancies (Keller & Lamandé, 2010)

21 21 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Stress propagation in soil: Simulation vs. measurements (typical result) Possible reasons (Keller & Lamandé, 2010): (1)Upper model boundary condition is wrong (2)Model for stress propagation is inappropriate (3)Stress measurements are inaccurate Keller T & Lamandé M (2010) Challenges in the development of analytical soil compaction models. Soil & Tillage Research 111,

22 22 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Stress propagation in soil: towards a 2-layer approach A pragmatic model would be: 1)Tilled layer (e.g m depth) : no stress attenuation 2)Subsoil: according to Söhne (1953)

23 23 Simulations of σ z with different values for concentration factor ( ν). Field measure- ments of σ z Comparison: When (at which ν ) does the simulated σ z fit best the measured σ z (lowest RMSE)? Estimation of the concentration factor: Approach (i) Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

24 24 ν = f (soil properties, loading) Linear regression model (which soil properties and loading characteristics describe best the optimized ν ?) Estimation of the concentration factor: Approach (ii) Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

25 25 Regression for data from wheeling experiments on seven soils (12 -61% clay) yields: σ pc ↑  ν ↓ Sand ↑  ν ↑ σ pc [kPa] Sand [%] Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART Keller T, Stettler M, Arvidsson J, Lamandé M, Schjønning P, Berli M & Rydberg T (2009) Stress propagation in arable soil: determination and estimation of the concentration factor. Proc. 18th Conf. ISTRO, Izmir, Turkey, June Estimation of the concentration factor: Results from a preliminary study

26 Federal Department of Economic Affairs FDEA Agroscope Reckenholz-Tänikon Research Station ART 6c. WP1: Soil mechanical models and pedotransfer functions

27 27 1.Model approach 2.Estimation of model parameters Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

28 28 1. Modelling approach: a) upper model boundary condition (i) ? Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Contact area Stress distribution Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

29 29 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 1. Modelling approach: a) upper model boundary condition (ii) Empirical models for each of the FRIDA model paremeters Upper model boundary condition Easily-available tyre/loading properties (e.g., tyre dimensions, tyre inflation pressure, wheel load) and information on soil condition/consistency Model ‘FRIDA’: (Keller, 2005; Schjønning et al. 2008) Parameters: 1.Contact area: l and w, n, 2.Stress distribution: α and  e.g.:  = a P tyre + b P WheelLoad

30 30 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 1. Modelling approach: b) stress propagation A new semi-empirical model: 1)Tilled layer (e.g m depth) : no stress attenuation 2)Subsoil: according to Söhne (1953) „Classical“ one-layer model (Söhne, 1953) Compare, and select the best performing model…

31 31 1. Modelling approach: c) compressive soil strength Pragmatic model: CS = k x PCS where: CS = compressive strength (kPa) PCS = precompression stress (kPa) k = empirical factor (-), k = 0..1 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

32 32 1.Model approach 2.Estimation of model parameters Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

33 33 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 2. Estimation of model parameters: a) upper model boundary condition (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

34 34 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 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

35 35 Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART 2. Estimation of model parameters: c) soil strength 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

36 Federal Department of Economic Affairs FDEA Agroscope Reckenholz-Tänikon Research Station ART 7c. Structure of soil and weather data bases, Switzerland Thomas Keller 1,2 and Matthias Stettler 3 1 Agroscope Reckenholz-Tänikon Research Station ART, Reckenholzstrasse 191, CH-8046 Zürich, Switzerland; 2 Swedish University of Agricultural Sciences, Department of Soil and Environment, Box 7014, SE Uppsala, Sweden 3 Swiss College of Agriculture, Länggasse 85, CH-3052 Zollikofen,

37 37 A. Soil data  A national soil database does not exist…, but is in progress (however, to be expected after the end of PredICTor)…  Some counties („Kantons“) do have GIS-based soil maps (  perhaps this could be used as a pilot study area)  Best soil map of Switzerland: „Soil suitability map“ (suitability with regard to agricultural production; „Bodeneignungskarte“) 1:200‘000  Some counties do have soil maps 1:5‘000 to 1:25‘000  Problem: existing soil data and maps are rather descriptive (e.g. no exact values of clay content but only classes) Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART

38 38 B. Meteorological data  Agroscope ART has direct access to about 60 official (Meteo Switzerland) weather stations of Switzerland (hereby, data from these weather stations are mirrored to a database on an institute server every night)  The data includes prognosis of the coming two days  Data from the database could be accessed from Terranimo ® (discussed and confirmed at a meeting in Zürich last October) Thomas Keller | © Agroscope Reckenholz-Tänikon Research Station ART


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