Soil Traffichability Study Based On Mechanical Properties Of Paddy Soil

Total area of paddy soil in China amounts to 4 hundred and 50 million Mu. Paddy soil environment affects vehicle performance and traffickability, which has a direct influence on fuel consumption, and further contributes to a higher cost of food production in paddy soils. As most of soils in Jiangsu province were clayey or adhesive, soil traffickability was largely degraded due to severe traffic sinkage and increased impedance. Therefore it is practically significant to study traffickability in paddy soil conditions.Soil was spatially and mechanically heterogeneous. And soil’s heterogeneity was observable in different scales. Thus measuring and assessing soil physical and mechanical properties in a finer scale should be helpful for the development of refined soil traffickability research. In this research a package of tools was used to measure paddy soil physical and mechanical properties in refined scales. There indices were used to assess soil mechanical behavior and traffickability. The measured soil physical properties were related to soil moisture content, soil bulk density and total porosity. Soil mechanical properties included c、φ、kc、kφ、n, among which c and φ were soil shearing properties, while kc、kφ、n were soil bearing capacities.The measured results revealed significant heterogeneities of paddy soil physical and mechanical states, even in mini-scales. This implies that soil traffickability may change even in micro-scales. Soil penetration test illustrated the changing property of soil penetration strength along the depth. Soil moisture content, soil dry bulk density and total porosity varied largely with soil depth. A sectioned curve-fitting was implemented on the measured soil penetration curves, providing a characteristic function of soil penetration with respect to soil depth.Soil traffickability is governed by a set of indices, which is composed of soil cohesion c、internal friction angle φ and kc、kφ、n for soil bearing capacities. The refined measuring tools used in this research include laminated sampling soil with 2 cm thick sampling cores, followed with direct shear test for soil cohesion and internal friction angle, and plate sinkage test for kc、kφ、n in different plate sizes. The measured soil parameters were then applied on models of soil traffickability prediction.In-situ soil bearing capacity was measured with a number of penetration tools, including a cone and 3 plates in 20,30 and 50 mm in size, respectively. The acquired result revealed both cone and 20 mm diameter plate had a coning effect. While the 30 mm and the 50 mm plates behaved in plating effect. This difference proved a fact that soil bearing capacity was determined by the contacting area between soil and tyre. And such a relation would has its implications on agricultural vehicle tyre designs.Soil traffickability in the test site was evaluated with related models and the measured data. Three typical tractors extended in Jiangsu province were selected for the assessment. The calculated result proved that all the 3 tractors were well in traffickability in the measured soil conditions. Soil traffickability in deeper soil layers was higher than the top layer.