干陸ほ場におけるトラクタの走行性について(1) : 膨軟土壌状態における車輪の沈下

For the improvement of working efficiency by the tractor, trafficability, especially in Japan, the sinkage of tractor on the wet field is a important problem.
Therefore, we investigated the relation between the sinkage of wheel and soil moisture on the soft reclaimed soil using by model tractor, indoors.
The device of the model tractor used in this test was enable to keep always constant weight on the tractor wheel by the special mechanism, although a tractor usually arise weight transfer on its wheel from running or pulling some loads.
Main test results are as follows ;
1) The sinkage of wheel has a linear relation to weight on the tractor wheel in high soil moisture, while parabolic increase in low soil moisture. It is due to an alteration of soil character caused by the change of soil moisture.
The sinkage makes a rapid increase when the dry basis soil moisture content becomes 55 and over.
2) The sinkage of wheel at the maximum silppage increases as S type curve with weight on the tractor wheel in the condition of low soil moisture, while as parabolic curve in high soil moisture.
3) The bearing capacity of soil is comparably large at the dry basis soil moisture content of almost 50. The slippage caused by wheel slip and soil adhesion to the test wheel increases rapidly at the dry bases soil moisture content of 60-80.