通过野外现场调查、载荷试验、轻型圆锥动力触探、车辆碾压原状草地观测试验及室内试验方法,对呼伦贝尔沙质草原不同碾压程度表层沙土物理力学性质及变形和剪切破坏特征进行研究。结果表明:碾压使上软下硬高压缩性的原状表层沙土因应力集中产生振动密实沉降、塑性变形,直接破坏表土层原状结构。碾压程度越大,沙土密实度越高、抗剪强度越大、承载力越高。碾压形成上硬下软土层,因强度不足发生整体剪切破坏,塑性变形区的沙土在重复荷载作用下产生振动蠕变及砂土液化,使土层强度、稳定性显著降低。车辆碾压可直接或间接破坏沙质草原表层沙土,加剧土层破口形成及扩大,加速草原沙漠化。

Topsoil mantle is very important in grassland protection against sandy desertification in the form of blowouts. Regardless many researches, little attention has been paid on the destructive impacts of vehicle traffic on the topsoil mantle. In this research, field investigation, load test, light cone dynamic penetration, and laboratory tests was applied to assess the impacts of vehicle traffic on the topsoil physic-mechanical and shear deformation properties, at different erosion extent regarding the topsoil mantle ranging at the depths from zero to thirty centimeter. It was discovered that in contrast with the original grassland, topsoil compressibility decrease, shearing strength and bearing capacity increase, along with the increase of the depth of tracks in use by off road vehicles. The topsoil surface hardens quicker than the lower level, accelerating grassland vegetation degradation. Insufficient of the bearing capacity result in overall shear failure and entailed vibration creep or liquefaction makes the soil mantle out of stability and to dismantle. Vehicle compact on the original grassland topsoil mantle resulted in vibration compaction settlement and irreversible shear deformation, destructed topsoil mantle original structure due to its higher compressibility and stress concentration phenomena. Therefore off road vehicle traffic facilitates wind and/or runoff to create holes in the topsoil to generate blowouts, and then large scale sandy desertification occurs.