Trafficability of Wheels on Farm Lands with Hard Pan (Two-Layer Soil)

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1) The non-vertical penetration test apparatus was developed, which enables us to alter a penetration angle from 90 (vertical) to 30 degrees in every 15 degree and a depth of soil layer. By the use of this apparatus the vertical and horizontal soil reaction with variations of a penetration angle and a depth of soil were measured. Besides, the soil reaction for the vertical penetration was analyzed by the slip-line method. The good coincidence of the experimental and the analytical results was attained.2) The test apparatus for traveling performance was developed, in which the wheel-system is connected with the carriage through a linear bearing system so that it does not incline and the contact load is kept constant even when a sinkage changes. Further, the T-shaped sensors are attached to the wheel surface in order to measure distributions of a normal and tangential stress.3) A new method for measuring soil deformation was developed: A few hundred markers, the diameter of which is 5mm … More and which are printed a black cross, are fitted on the inside wall of an acryl plate by water in appropriate intervals and move with a movement of soil particles.4) The subloading surface model was extended so as to describe the induced anisotropy which proceeds with the deformation of soil for a large slippage.5) Introducing the subloading surface model, the programming of the finite element method for elastoplastic deformation was developed. In this program the boundary condition in the contact surface between a wheel and soil was improved so as to slip satisfying the Coulomb friction. Further, the controlling program for keeping the contact load constant was incorporated, by which the sinkage with a slip became able to be analyzed.6) By the use of the finite element program the numerical calculation was per formed under the same conditions as those in the experiments. The analytical results express well the trends of experiments for the net traction, the axle-torque, the normal and tangential stress on wheel surface and the deformation of soil. Less