山地履带拖拉机坡地等高线作业土壤压实应力研究

Distribution of Soil Compaction Stress during Contour Line Operation of Hillside Crawler Tractor

山地履带拖拉机(配备姿态调整机构)具有良好的稳定性和越障性能,特别适宜在丘陵山区坡地作业,然而由于坡地角的存在导致拖拉机两侧履带下的应力分布极不均匀,使得拖拉机附着性和通过性均降低。本文针对山地履带拖拉机坡地等高线行驶/作业时,坡地土壤内部应力分布规律不明确以及如何提高应力均匀性缓解土壤压实等问题,在深入分析坡地工况下履带最大接地比压与应力传递基本规律的基础上,采用EDEMRecurDyn耦合方法进行了仿真试验,并采取土压力盒埋设法分别开展了基于小型坡地土槽的静态试验和坡地试验田的动态试验;其中,静态试验探究了不同深度土壤在含水率、初始紧实度、加载质量及坡地角等影响下的垂直应力分布规律;动态试验探究了山地履带拖拉机坡地等高线行驶/旋耕作业时履带下方土壤应力随作业速度、车身状态(调平/未调平)及牵引负载的变化规律;并分析了履带张紧力对土壤垂直、水平应力分布的影响。试验结果表明:履带下垂直应力在各支重轮的轴线处呈现一个应力峰值;水平应力在各支重轮轴线的前、后方分别出现一个应力峰值;适当增大作业速度,可减小土壤内部垂直和水平应力峰值,拖拉机速度由0.5 km/h增加到1.5 km/h,垂直应力峰值减小了35%,水平应力峰值减小了27%;车身调平可以较好地提高拖拉机两侧履带下土壤垂直、水平应力分布的均匀性,坡低、坡高两侧的垂直应力峰值分别降低13%和增加18%,坡低、坡高两侧的水平应力峰值分别降低28%和增加23%;履带张紧力由1.2×10^(4) kPa减小到8.0×10^(3) kPa时,履带下的垂直及水平应力峰值分别减小了31%和22%,即适度减小履带张紧力可降低土壤压实程度。该研究可为山地履带拖拉机相关参数的优化提供理论依据,可提高坡地土壤应力分布均匀性、缓解土壤压实效应。

Hillside crawler tractor(equipped with attitude adjustment mechanism)has good stability and obstacle-surmounting performance,and it is especially suitable for operation on hilly and mountainous slopes.However,due to the existence of the slope angle,the stress distribution under the tracks on both sides of the tractor is extremely uneven,which reduces the adhesion and passability of the tractor.Aiming at the problem that the internal stress distribution law of sloping soil is not clear when the hillside crawler tractor is driving and operating on the contour line slope,on the basis of in-depth analysis of the basic laws of the maximum grounding specific pressure and stress transfer of the crawler under sloping conditions,the EDEMRecurDyn coupling method was used to carry out the simulation test,and the method of burying the soil pressure sensor was used to carry out the static test based on the small slope soil trench and the dynamic test on the slope field respectively.The static test explored the vertical stress distribution law of soil at different depths under the influence of moisture content,initial compactness,loading quality and slope angle.The variation law of the vertical,horizontal and lateral stresses of soil under the crawler with operating speed,state of the tractor body(leveled and unleveled)and the load when the tractor drive and rotary tillage on the contour line slope was studied by dynamic tests.And the influence of crawler tension on soil vertical and horizontal stress distribution was analyzed.The results showed that the vertical stress under the crawler presented a stress peak at the axis of each roller.The horizontal stress had a stress peak at the front and rear of each roller axis.Appropriately increasing the operating speed can reduce the peak value of vertical and horizontal stress in the soil.When the tractor speed was increased from 0.5 km/h to 1.5 km/h,the peak value of vertical stress was reduced by 35%,and the peak value of horizontal stress was reduced by 27%.The leveling of the tractor body can better improve the uniformity of vertical and horizontal stress distribution under the crawler on both sides.The vertical stress peaks on the low and high sides of the slope were respectively decreased by 13%and increased by 18%,and the horizontal stress peaks on the low and high sides of the slope were respectively decreased by 28%and increased by 23%.When the crawler tension was reduced from 1.2×10^(4) kPa to 8.0×10^(3) kPa,the vertical and horizontal stress peaks were respectively decreased by 31%and 22%,which showed that moderately reducing crawler tension reduced soil compaction.The research result can provide a theoretical basis for the optimization of relevant parameters of hillside crawler tractors,so as to improve the uniformity of soil stress distribution on slopes and alleviate the soil compaction.