2020 年 14 巻 6 号 p. JAMDSM0084
The depth of tilting in agricultural soil is 30–40 cm, which approximates the equivalent contact diameter of tires for the off-road vehicle. The soil thus tends to have an upper loose layer and a hard layer underneath, which leads to changes in the soil behavior. The effect of the hard layer can be defined by determining a specific point (breaking point) in the pressure (p)-sinkage (z) curve. The present study aims to design and construct a bevameter instrument can be used to simulate the hard layer in soil. Besides, specifying the breaking point and the effect of the hard layer on the soil behavior. In addition to the feature of a high applied load can be measured, the significance of this device comes from the easiness of changing the thickness of the soil which is in demand to be investigated. The device includes a mechanical structure, a hydraulic system, measuring sensors, and a data collection unit. Two sinkage plates with different diameter were employed for characterizing the relationship between the applied load (applied pressure) and the vertical deformation (sinkage). Indoor tests were also conducted to evaluate the device’s performance and study soil penetration resistance. The test was developed using sandy loam soil sieved through a 0.5 mm mesh. The soil bin was filled with soil up to 0.3 m thickness as a layer of 0.1 m. The soil density and moisture content for the soil was calculated as 1.245 g/cm3 and 12.3%, respectively. The device’s results showed that the hard layer changes the soil’s behavior as the soil becomes more compact. This layer also increased the values of sinkage exponent (n) and sinkage modulus (k) and implicitly modified the soil properties. Many experiments were carried out and discussed to validate the results.
