Uniaxial compression data

Uniaxial compression data from samples collected at three different depths (0-5, 10-15 and 20-25 cm) from different fields in Southern Minas Gerais state, Southeastern Brazil, annually cultivated with corn for silage production.
Samples were collected according to a spatially-stratified design. In each sampling point, six undisturbed soil samples were collected (within metallic cylinders 2.5 cm high and 6.4 cm wide), a replicate pair in each of the sampling depths: 0-5 cm, 10-15 cm, and 20-25 cm. A set of 76 sampling points was distributed in the three fields (field 1A: 22 points in 6.2 ha; field 1B: 29 points in 15.6 ha; field 2A: 25 points in 7.6 ha), totalling 456 samples.
The samples were saturated and set to equilibrate at water tensions of 10 or 100 kPa (half the samples at each water potential). These water tensions were chosen because silage harvesting usually occurs during the rainy season and the soil is therefore expected to be moist. The samples were then submitted to drained, confined uniaxial compression tests on electric-pneumatic consolidometers (model S-450, Durham GeoSlope, USA). A stress sequence of 25, 50, 100, 200, 400, 800 and 1600 kPa was applied to the samples for eight minutes per load step without decompression between each step.
reference: field, depth and water tension;
field: identifies sampling field r1, r2 and ed, respectively 1A, 1B and 2A in the attached figure;
depth: sampling depth (0-5, 10-15 and 20-25 cm);
psi: water potential (in kPa) as numeric variable (10 or 100 kPa);
tensao: water potential (in kPa) as categorical variable (10 or 100 kPa);
Dsmax: maximum bulk density from the standard Proctor test (Mg/m3);
sample: sample identification number (each undisturbed sample was collected within metallic rings 6.4 cm wide and 2.5 cm high);
load: applied loads (in kPa) during the uniaxial compression tests (25, 50, 100, 200, 400, 800 and 1600 kPa);
w: weght basis water content (g/g);
teta: volume basis water content (m3/m3);
db0: initial bulk density (that is, before compression) in Mg/m3;
e: initial void ratio (that is, before compression);
n: initial total porosity (that is, before compression) in m3/m3;
sat: initial degree of satuartion (that is, before compression);
air: initial air-filled porosity (that is, before compression), calculated as the difference between total porosity and water content;
dbi: bulk density at each applied load level;
GC: degree of compaction (dbi/Dsmax) at each applied load level;
ei: void ratio at each applied load level;
ni: total porosity at each applied load level;
strain: vertical deformation at each applied load level;
sati: degree of saturation at each applied load level;
airi: air-filled porosity at each applied load level;
deriv.ro: rate of change in bulk density at each load increment;
deriv.e: rate of change in void ratio at each load increment;
deriv.n: rate of change in total porosity at each load increment;
deriv.str: rate of change in strain at each load increment.

该数据集收集了来自巴西东南部米纳斯吉拉斯州南部不同地块（0-5厘米、10-15厘米和20-25厘米深度）的年度玉米青贮生产样品的单轴压缩数据。样品按照空间分层设计进行采集。在每个采样点，采集了六个未扰动的土壤样品（直径6.4厘米、高2.5厘米的金属圆柱体内），每个采样深度（0-5厘米、10-15厘米和20-25厘米）均有一对重复样品。三个地块（1A地块：6.2公顷内22个采样点；1B地块：15.6公顷内29个采样点；2A地块：7.6公顷内25个采样点）共分布了76个采样点，总计456个样品。样品被充分饱和并设置在10或100千帕（每个水势下各半）的水张力下达到平衡。选择这些水张力是因为青贮收获通常发生在雨季，因此土壤预期将是湿润的。随后，样品在电-气固结仪（Durham GeoSlope，美国，型号S-450）上进行了排水的、约束的单轴压缩试验。对样品施加了25、50、100、200、400、800和1600千帕的应力序列，每个载荷步持续八分钟，各步之间不进行减压。参考信息包括地块、深度和水张力；地块：标识采样地块r1、r2和ed，分别对应附图中1A、1B和2A；深度：采样深度（0-5厘米、10-15厘米和20-25厘米）；psi：水势（以千帕为数值变量，10或100千帕）；tensao：水势（以千帕为分类变量，10或100千帕）；Dsmax：标准Proctor试验的最大干密度（Mg/m³）；sample：样品标识号（每个未扰动的样品均在直径6.4厘米、高2.5厘米的金属圆环内采集）；load：单轴压缩试验中施加的载荷（千帕，25、50、100、200、400、800和1600千帕）；w：重量基础水分含量（g/g）；teta：体积基础水分含量（m³/m³）；db0：初始干密度（即压缩前）（Mg/m³）；e：初始孔隙比（即压缩前）；n：初始总孔隙率（即压缩前）（m³/m³）；sat：初始饱和度（即压缩前）；air：初始空气孔隙率（即压缩前），计算为总孔隙率与水分含量的差值；dbi：每个施加载荷水平下的干密度；GC：每个施加载荷水平下的压实度（dbi/Dsmax）；ei：每个施加载荷水平下的孔隙比；ni：每个施加载荷水平下的总孔隙率；strain：每个施加载荷水平下的垂直变形；sati：每个施加载荷水平下的饱和度；airi：每个施加载荷水平下的空气孔隙率；deriv.ro：每个载荷增量下干密度的变化率；deriv.e：每个载荷增量下孔隙比的变化率；deriv.n：每个载荷增量下总孔隙率的变化率；deriv.str：每个载荷增量下应变的变化率。