Test Dataset of Free Iron Oxide Content - Moisture Content - Color Parameters - Shear Strength of Granitic Residual Soil in Guangxi Area

This dataset was generated from a series of laboratory tests on granitic residual soil collected from construction sites in Guangxi Area (spatial scope: 22°N–26°N latitude, 104°E–112°E longitude), covering typical granitic residual soil distribution zones in the region. The sampling work was conducted from March 2022 to June 2022 (temporal scope), with a total of 30 undisturbed soil samples collected from 5 different locations (6 samples per location) to ensure the representativeness of regional soil properties. The dataset generation process included three key stages: sample preparation, parameter testing, and data processing. First, the collected undisturbed samples were air-dried, crushed, and sieved through a 2 mm sieve to remove gravel and impurities, then prepared into remolded soil samples with different moisture contents (5%–25%, interval 5%) and free iron oxide (Fed) contents (0%–25%, adjusted by adding ferric oxide powder and chemical reduction method). Second, relevant parameters were tested using professional equipment: color parameters (CIE-L*a*b* system) were measured by a CR-400 chroma meter (Konica Minolta, Japan); free iron oxide content was determined via the dithionite-citrate-bicarbonate (DCB) extraction method with a UV-Vis spectrophotometer (UV-2600, Shimadzu, Japan); shear strength indices (cohesion c and internal friction angle φ) were obtained through direct shear tests using a ZJ-type strain-controlled direct shear apparatus (Nanjing Soil Instrument Factory, China), with a shear rate of 0.8 mm/min and normal stresses of 100 kPa, 200 kPa, 300 kPa, and 400 kPa. Finally, the test data were processed using Excel 2019 and Origin 2021: raw data were sorted to remove abnormal values caused by instrument fluctuations, and average values of three parallel tests were calculated to ensure data reliability.The dataset consists of 1 Excel file (file name: Guangxi_Granitic_Residual_Soil_Test_Data.xlsx) containing 150 records (30 samples × 5 moisture content gradients), Free Iron Oxide Content (Fed, unit: %), Moisture Content (unit: %), L* (lightness value, dimensionless), a* (red-green axis value, dimensionless), b* (yellow-blue axis value, dimensionless), Normal Stress (unit: kPa), Shear Stress (unit: kPa), Cohesion c (unit: kPa), Internal Friction Angle φ (unit: °), and Test Date (date of parameter testing). All data are complete without missing values, as abnormal test results were remeasured immediately to ensure data integrity. The potential errors in the dataset mainly come from two aspects: instrumental error (chroma meter accuracy ±0.01, spectrophotometer absorbance error ±0.001, direct shear apparatus force measurement error ±1%) and operational error (sample weighing error ±0.01 g, moisture content control error ±0.5%). These errors are within the allowable range of geotechnical test specifications (GB/T 50123-2019) and do not affect the reliability of the data.The dataset is stored in Excel format, which is compatible with common software such as Microsoft Excel, WPS, and Origin, and no special software is required for opening and analyzing. The data can be used for research on the correlation between color parameters and mechanical properties of granitic residual soil, the influence mechanism of free iron oxide and moisture content on soil shear strength, and the development of regional soil property prediction models, providing basic data support for geotechnical engineering design and disaster prevention in Guangxi Area.