秸秆覆盖下土壤耕作非线性动态过程研究

[目的] 本文旨在研究秸秆和土壤颗粒从固态到流态转变的非线性运动过程。[方法] 推导建立土壤固态-流态转变非线性动态过程本构方程,基于离散单元法(DEM),模拟研究推土板在草颗粒影响下的阻力变化;搭建含秸秆耕作试验平台,建立7、13和19 mm 3种尺寸的秸秆离散元模型。[结果] 由于耕作过程改变了其原有土壤的表面形态,耕作后的土壤孔隙比增加,犁后出现明显的浅沟;随着耕作的不断推进,部分颗粒会受到二次切割分离;牵引速度越大,圆盘犁面前缘隆起土颗粒越多,犁面前缘所受土壤的阻力越大,所需牵引力越大;7和19 mm秸秆向两侧位移明显,而13 mm秸秆沿犁面前缘位移明显,该尺寸秸秆与犁面发生二次接触,导致速度变化明显。[结论] 耕作过程中秸秆与土壤破碎颗粒均发生复杂的非线性动态运动,物理力学性能发生不同变化,进而影响农机具的牵引功率。
[Objectives] The purpose of this paper is to study the nonlinear dynamic process of soil and straw particles from solid to liquid state.[Methods] With the soil constitutive equation of nonlinear dynamic process form solid to liquid state derived and established,and by discrete element method (DEM),the study simulated the resistance change of bulldozing plate under the influence of particle in the grass,and set up the straw tillage experimental platform and straw discrete element models of three different sizes which were 7,13 and 19 mm.[Results] Because the tillage process changed original soil surface morphology,the soil void ratio increased after the tillage,and obvious shallow gullies appeared after the plough. With continuously promoting the process of tillage,some particles were cut to separate twice. The higher the haulage speed was,the more soil particles were uplifted by disc plough onto the front edge of plough,the greater resistance was provided by soil onto the front edge of plough,the grater the traction was. The displacement of 7 and 19 mm straws to the both sides were obvious,while the displacement of 13 mm straw along the front edge of plough was obvious. 13 mm straw contacted the plough surface again,which led to a significant change in speed.[Conclusions] The broken particles of straw and soil also showed complicated nonlinear dynamic motion in tillage process,and its physical and mechanical performance changed differently,which affected the traction power of agricultural implement in turn