Abstract: Alfalfa soil compaction by mowing machine was simulated using software PlAXIS on the basis of experiments to investigate compacted soil internal stress and displacement variation. Results showed that the stress under the middle of wheel tack was higher than the edge of wheel tack and soil stress range in size from 0 to 20 cm was higher than others. The effect range of soil stress caused by compaction was extended with the increase of rolling compaction. The change area of soil surface stress along the horizontal direction matched tire contact area and the area of stress gradually expanded along the vertical direction. Soil aggregates were damaged when the stress reached a maximum value with the increase of rolling compaction. Soil settlement gradually occurred from 0 to 30 cm depth with the increase of rolling compaction. The first compaction played an important role in soil settlement and then reduced gradually until soil yield. Comparative analyses between the forecasted value and measured value indicated that there was very little forecast error in predicted value. Therefore, software PLAXIS has a certain practical significance to forecast soil compaction.

Key words: Soil compaction, Finite element simulation, Soil stress

摘要： 为研究压实后土壤内部应力及位移的变化规律，在割草机对苜蓿（Medicago sativa）地土壤压实试验的基础上，基于PLAXIS软件对苜蓿地土壤压实进行了有限元模拟。结果表明：车辙中线下方土壤应力较轮胎边缘下方大，土壤应力较大部位出现在0～20 cm范围内，各部位应力分布不平衡，随碾压次数的增多，应力增加范围由地表向下延伸，由轮辙中线向轮辙边缘逐步扩大；沿水平方向的地表应力变化区域与轮胎接地面积相当，沿竖直方向向下，其变化范围逐步扩大，大应力区域为一以轮胎接地面积为底的锥形区域，轮辙下部的土壤形成一个较硬的应力核，其最大应力处于该核的中心，并由此向外应力逐步减小；应力核的中心部位，应力达到最大值后，随碾压次数的增加，土壤团聚结构会被破坏，土壤出现屈服；随着碾压次数的增多，0～30 cm深度上的土层均逐步沉降，沉降主要是第1次碾压所致，之后逐步减弱，直至土壤失效；通过软件对土壤压缩量的预测值与实测值对比分析发现，该软件对表层轮辄深度的预测误差较小，应用PLAXIS软件对土壤压实进行预测具有一定的实用意义。

关键词: 土壤压实, 有限元模拟, 土壤应力