Study On The Mechanical Driving Performances Of Vehicle In Soft Soil

When a vehicle is walking in soft soil, the stress distribution from the contacting terra to the vehicle is a complex process. Sinkage of wheel occurs and the driving impedance is increased, which results into a worsened trafficability. This is mainly due to the high moisture content, poor adhesion, increased road impedance and the rheological properties of the terra soil. Therefore only the specially designed vehicle can satisfy this type of trafficablilty demand, and the research on the pulling performance of a vehicle under soft soil condition has its own significance.Trafficablilty is a main index for the performance of off-road vehicles and agricultural vehicles. The development of increased vehicle trafficability is thus a fundamental and effective means of solving the maneuvering of vehicle in terra conditions. The soil-terra theory indicated that the wheel-soil relation is the core of the problem of the research and the development of higher performance off-road vehicles.The development of agricultural mechanization brings forward an impressing issue: vehicle trafficability in soft soils. In tradition, soils were treated and simplified either as elastic, plastic or elastic-plastic media if the interaction between a vehicle waling mechanism and the terra was taken as a focus. This treatment was no longer suitable for the high moisture content soft soils.In this work the influence of soil on the wheel was studied, especially the real mechanical effect of the agricultural soil and its load bearing characteristics. By sampling the field soil and remolding and controlling its physical characteristics, plate sinkage test was conducted. The result shown that the Bekker load-bearing model was no longer suitable for soft soil. Through the direct shear test it was found that the soft soil shear model was in accordance with the Janosi model. In addition, a fast and effective laboratory test procedure was designed to acquire soft soil load-bearing capacity and yielded satisfactory results. The load-bearing characteristics and the shear strength of remolded soft soil was reviewed, followed with plate sinkage test on the soil. The resultant load-bearing model was then compared with in-situ soil reactions. Additionally, direct shear test on remolded soil was conducted. To verify the real performances of the field soil, a Y-type soil penetrometer was reformed into a portable mini-plate sinkage meter for the quantification of field soil load-bearing capacity. Soil was also sampled and brought into laboratory for direct shear test.The load-bearing models from plate sinkage test and the shearing model from direct shear test of the agricultural soft soil had its own significance, due to a fact that the trafficability of off-road vehicle was mainly determined by the rolling resistance from soil deformation and the adhesive force, all of which can be predicted by soil mechanical models.Based on a semi-empirical method and the vehicle-terra interaction test, a single-wheel test platform was designed and constructed. The test of the platform was conducted to reveal the trafficablilty on soft soil, which provided the main index:drawbar pull (DP). This provided a basis for the method and suggestion for improving the trafficability of vehicle in soft soil.