Study On The Evaluation Of Soil Compaction By Agricultural Tire And Combination Shovel Loose Soil Technology

Currently,declining farmland and lower cultivated land quality has become increasingly serious problem in China.With the growing improvement of agricultural mechanization level,soil compaction gradually becomes one of the main reasons of soil degradation and decline of farmland quality.This paper selected the loam in North China as the research object,the compaction evaluation of agricultural machine and mechanization abatement technology as the research objectives,and main research contents included the primary and secondary analysis of the factors affecting the tire compaction,effect of the tire pressure,axle loading and compaction times on soil compressive stress transfer process,soil compaction prediction method based on tire and effect of soil compaction on soil properties and crop growth,and then putting forward a soil compaction reduction method by combined soil subsoiling technology.The main results are as follows:(1)The primary and secondary analysis of the factors affecting the tire compaction was studied.The results showed that tire axle load,tire pressure,and compaction times have significant effect on the soil compaction,while the tire aspect ratio and soil initial compactness have no significant effect on the difference of soil compaction.When the axle load ranged from 4.667 to 13 kN,the soil bulk density increased by 22.6%,the compactness increased by 25.3%.When the tire pressure changed from 85 to 210 kPa,both the soil bulk density and compactness increased by 18.1%.When the compaction times varied from 1 to 9,the soil bulk density increased by 24.9%and compactness increased by 51.5%.(2)Combined with numerical analysis,discrete element simulation and field experiment methods,the effect of tire pressure,axle loading and compaction times on soil compressive stress transfer process was studied.The results showed that the contacted soil area gradually decreased with the increasing tire pressure.The stress concentration on the contact surface was distributed from both sides of the tire to the center.When the pressure was 100 kPa,the maximum stress were 11.2%and 21.1%lower than that of 85 and 120 kPa,respectively.As the tire axial load increased,the contact area gradually increased,and the shape changed from an oval-like shape to a rectangle-like shape.Under a 50kN axle load condition,the soil contact area of the tire was 24.5%larger than that under 30kN,and it was 1%smaller than that under 70kN.With the increase of axial load,the contact surface stress concentration occurred at both sides.The maximum contact stress under 50kN axial load condition was 31.6%higher than that of 30kN and 10.3%lower than that under 70kN.Tire pressure can significantly increase the soil stress of soil layer depth from 0 to 40 cm,soil stress below 40 cm had no significant effect,and axial load can significantly increase the soil stress of soil layer depth from 0 to 80 cm.The increase of tire compaction times has a logarithmic function with increasing soil profile stress.(3)Based on the soil stress calculation model and combined with the soil shear strength and compressive strength,the soil compaction evaluation standard was constructed and verified through field test.The results showed that the 1 to 9 times compaction of the tractor with a load of 4155kg can cause the destructive plastic deformation on soil layer from 0 to 60cm,5 to 9 times compaction can cause the plastic deformation on soil layer from 0 to 80cm.The 1 to 3 times compaction of the tractor with a load of 1225kg can destroy 0 to 40cm soil structure,and the 3 to 7 times compaction can compact the 0 to 63cm soil layer,while the 7 to 9 times compaction can compact the 0 to 80cm soil layer,which achieved compact destroy.The results of compaction on soil bulk density and maize growth revealed that the critical value of soil bulk density for significantly reducing maize yield wasl.43g.cm-3.(4)In order to solve the problem of soil compaction,combined soil loosening technology has been presented.In the combination analysis of discrete element simulation and field experiment,the loosening technology of chisel shovel has more capable of disturbing the larger scope soil by the smaller resistance under the condition of soil depth of 300mm.The combination of airfoil and chisel shovel was the best combination to alleviate soil compaction under the condition of soil depth of 400mm.The combined effect of curved shovel and airfoil shovel for alleviate compaction was optimal under the condition of soil depth of 450mm.In 2013-2016,the prediction results of soil compaction in the tire walking area under no tillage farmland conditions were obtained.The average bulk density under the condition of soil depth of 0?10,10?20,20?30,30?40 and 40?50cm decreased by 17.5%,21.9%,25.2%,18.5%and 23.2%before soil loosening respectively.Combined soil loosening technology can achieve soil loosening uniformity in all directions.