Soil erodibility parameters for two soils with different soil moisture content evaluated with the mini-Jet Erosion Test (JET)
Description
Soil erosion by water leads to various surface water problems including sedimentation of streams and reservoirs, degradation of soil health, reduction of water quality, and other. Soil detachment by water can be described by the excess shear stress equation. Values of two physical soil erodibility parameters, erodibility coefficient and critical shear stress, presented in the non-linear excess shear stress equation can be generated with a laboratory mini-Jet Erosion Test (JET). Raw JET experiment data is scour depth versus time. This dataset contains the results of JET experiments on two studied soils: silty clay loam (soil I, 16% sand, 48% silt, 36% clay, 4.25% organic matter, 1.45 Mg/m3 bulk density) from a tilled row crop field and clay loam (soil II, 38% sand, 32% silt, 30% clay, 4.13% organic matter, 1.49 Mg/m3 bulk density) from an annually grazed pasture. A total of 32 JET experiments (17 for silty clay soil I and 15 for clay soil II) were conducted on the samples with 0 g to 423 g initially infiltrated masses of water. For each JET experiment, the scour depth was recorded as a function of time. The experiment ended when the scour depth did not change after at least two scouring periods, and 30 to 38 periods were needed to reach the equilibrium depth. During the experiments, the time step increased from 15 sec at the beginning to 300 seconds at the end. The final scour depth varied from the smallest of 31 cm for a 0 g water for silty clay loam soil to the deepest of 46 cm for clay soil. The data files in the dataset are organized by the soil type and sorted by the index for the mass of initially infiltrated water provided in the summary file.
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Steps to reproduce
The steps for conducting JET experiments can be divided into the following three categories: (i) soil preparation, (ii) initial soil sample infiltration, and (iii) scour depth test: (i) Soil preparation: Collected soils samples were first air dried and filtered using a standard size sieve No. 4 (4.75 mm), oven dried at 95 C for 24 hours, and then settled undisturbed in a closed container to allow moisture distribution to reach 5% equilibrium after 24 hours. A standard cylindrical mold (height of 12 cm; diameter of 10.16 cm; volume of 972 cm3) was used with a water-tight liner attached to the bottom to minimize water leakage. The prepared soil was added to the mold in three layers and each layer was compacted by manually dropping a rammer of 2.5 kg in weight 25 times from a height of 30 cm In accordance with ASTM Standard D698. Finally, a standard US size 40 mesh and a grade 4 filter paper were placed on top of the sample to prevent soil particles from being disturbed. (ii) Soil infiltration: An infiltration apparatus constructed from a PVC pipe, two outflow tubes, and a continuous water supply line was placed on top of the soil mold. Water was allowed to flow in and fill the apparatus to a 150 mm depth; any water above that depth was transferred out of the system through the outflow tube. The plastic membrane separating the mold and the infiltration apparatus was penetrated and water was allowed to infiltrate into the soil until the desired mass of water was reached on the underlying scale and the apparatus was detached, thus stopping further infiltration. (iii) JET experiment: The mini-JET apparatus consisted of a pressure head tank, water inflow and outflow, a submergence tank (soil specimen and standard mold), and a nozzle and depth gauge connected to a rotating plate. The nozzle on the rotating plate allowed the impinging jet of water to be disconnected from the soil specimen while still providing a constant water level in the submergence tank. The JET apparatus was connected to the pressure head tank by the inflow pipe and to a drain by the outflow pipe. The pressure head tank, while connected to a continuous water source, provided a consistent flow of water to maintain the pressure head of each test at 91 cm (36 in). The mold with initially moist soil after the infiltration step was attached to the JET apparatus, and a valve was opened to allow water from the pressure head tank to submerge the compacted soil. Once submerged, the depth gauge was used to record the scour depth. At each subsequent step, the nozzle was opened for a specified time interval (15 sec to 300 sec) and the scour depth was measured. This procedure continued with gradually increasing time intervals until scour depth did not change for at least two periods, and equilibrium scour depth was assumed to be reached. All scour depth values and the corresponding times were recorded in a spreadsheet.