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Soil mechanics and trafficability - EFFORTE Business Forum

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Presentation by Philippe Ruch

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Soil mechanics and trafficability - EFFORTE Business Forum

  1. 1. www.fcba.fr Soil mechanics and Trafficability EFFORTE KEY FINDINDS Philippe Ruch Institut Technologique FCBA EFFORTE Meeting _ June 17th, 2019
  2. 2. www.fcba.fr Sustainable forest soils management: a real challenge  Forest resource: trees/wood & “soil”  Soil ecosystem is rich and complex  Deepen our knowledge about the impact of forest machine on soil properties  Soil scientists defined a common protocol Climate change / Society's expectations with regard to forestry / Profitability of logging operations 2
  3. 3. www.fcba.fr 1. Resilience of soils to compaction compaction and shearundisturbed soil time ?? Or ?? Compaction has an high impact on soil functioning:  increase in bulk density, PR…  decrease in gas and water exchange capacity => mortality, in tree growth… Soil properties recovery takes time!
  4. 4. www.fcba.fr  Two long monitoring sites on forest soils compaction 4 Set up in 2007 & 2008 25 t loaded, 2 passes, mean rut depth 5 cm 50 cm thick silty loam layer laying on a clayey layer Resilience of soils to compaction
  5. 5. www.fcba.fr T C AZ: 11 years after compaction… Resilience of soils to compaction & Trafficability KF  The impact on PR decreased after 10 years only on the less acidic site.  Other soil properties have to be analysed  Plan the traffic of the forest machines to limit the cumulated impacted surfaces  Care about initial impact
  6. 6. www.fcba.fr 2. Soil trafficability key elements  Machine characteristics linked to trafficability  Soil characteristics linked to trafficability
  7. 7. www.fcba.fr Soil strength models KF The soil strength (PR) is controlled by moisture content (VWC), bulk density and clay content.  You have to know your soils (grain size distribution…)  You have to know the VWC(%) Models developed by Luke between PR, moisture content and bulk density
  8. 8. www.fcba.fr Models for Rut depth, VWC and cumulative mass KF Rut depths can be predicted with moisture content and the cumulative mass driven over measurement point.  You have to know the VWC(%)  Adapt, if possible, the circulation plan so as to reduce the cumulative mass driven over each point Models developed by Luke valid for conventional 8-wheeled forest machines predicting rut depth = f(VWC & tons)
  9. 9. www.fcba.fr 9 Model for soil moisture behaviour in compacted soils KF simulated measured ET0 : Evapotranspiration of reference Amount of water that could evaporate or sweat through the tree when supply is sufficient Rain Predictive model Defined for 1 configuration of soil+stand and for 1 traffic threshold Day of traffic (delay after the rain when the soil has good bearing capacity)
  10. 10. www.fcba.fr 10 VWV threshold 32% example Predictive model for:  silty soil and a decidous forest in plains  1 trafficability threshold Easily reproductible June - August January - March Model for soil moisture behaviour in compacted soils KF
  11. 11. www.fcba.fr Machine characteristics 11 Front axle Rear axle T. Nordfjell Unloaded forwarder 56% 44% 57 models Loaded forwarder 39% 61% KWF Unloaded forwarder 60% 40% 16 models Loaded forwarder 33% 67%
  12. 12. www.fcba.fr 12 Model/Modèle Komatsu 860.4 John Deere 810D Load capacity/capacité de charge 14 T 9 T Tyres/pneumatiques Allianz Forestar 710/45-26,5 Nokian TRS2 600/50-22,5 Tyre inflation pressure/pression de gonflage 4,1 bar 4,0 bar Empty weight/masse à vide 19 340 kg 13 950 kg Loaded weight/masse en charge 31 260 kg 21 950 kg Load during the tests/masse transportée pendant les tests 11 920 kg 8 000 kg Machine characteristics
  13. 13. www.fcba.fr 13 0.00 0.20 0.40 0.60 0.80 1.00 1.20 1.40 1.60 1.80 LF1 LF2 LR1 LR2 RF1 RF2 RR1 RR2 kg/cm2 Nominal Ground Pressure per wheel (forwarder loaded) JD810D Komatsu 860-4 Nominal groud pressure
  14. 14. www.fcba.fr Ground pressure per wheel 14 Load per wheel (kg) Front/Avant Arrière/rear Buffalo 2 750 4 975 Gazelle 2 375 3 500 LVS520 1 150 2 350 Buffalo 36% 64% Gazelle 40% 60% LVS520 33% 67%
  15. 15. www.fcba.fr Stresses larger for the heaviest machines 14 T forwarder on wet soil – risk of subsoil compaction Azerailles Arc-et-Senans ”50-50 rule”: >50 kPa (0.5 bar) at 50 cm depth – risk of subsoil compaction ”50-50 rule”: >50 kPa (0.5 bar) at 50 cm depth – risk of subsoil compaction Higher wheel load results in higher soil stress Komatsu 860.4 KF
  16. 16. www.fcba.fr Ground pressure increases over the years 17  Reduce wheel loads and not only ground pressure contact 2,00 2,50 3,00 3,50 4,00 4,50 5,00 1993 1997 2004 2017 2019 Wheelload(T) John Deere 12T capacity Mean Rear wheel 12,9 T 17,1 T
  17. 17. www.fcba.fr Rutting, cumulative mass, critical VWC and modelisation 18 Novotny LVS5000 : 14T John Deere 810D : 22 T Ponsse Gazelle : 23,5 T Ponsse Buffalo : 31T John Deere 1510E : 32,5 T VWC 25% ou VWC 42% Novotny, Buffalo et Gazelle VWC Buffalo et Gazelle 42% Forwarder Total load (tons) Max. rut depth (cm) VWC H% critical 10T 140 10 0.38 10T 140 20 0.49* 14T 140 10 0.27 14T 140 20 0.35
  18. 18. www.fcba.fr Conclusion: results & next steps  3 deliverables, scientific papers, technical reports…  Recommendations for forest owners, forest practitioners & machine manufacturers / focus on fine and mid-grained grained mineral soils  Joint recommendations and country specifications (in addition or completion of existing guides)  => Future research is needed (models for other soil types…)  => Models developed could be used for applications 19
  19. 19. www.fcba.fr My deepest thanks to all the teams & Thank you for your attention 20 Philippe RUCH FCBA Equipe Appro (F) 21170 Charrey / Saône 03.80.36.36.20 philippe.ruch@fcba.fr

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