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ZHAO Xiu-feng,GAO Xiao-li,CAO Lei,CAO Jing-yang,LU Xin-cheng.Preparation of Certified Reference Materials for Soil Limit Water Content[J].Rock and Mineral Analysis,2021,(4):583-592
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Preparation of Certified Reference Materials for Soil Limit Water Content
Received:August 28, 2020  Revised:May 06, 2021
DOI:10.15898/j.cnki.11-2131/td.202008280119
Key words: soil  limit water content  reference material  certified value  uncertainty
Author NameAffiliation
ZHAO Xiu-feng Geological Survey of Jiangsu Province, Nanjing 210018, China 
GAO Xiao-li Geological Survey of Jiangsu Province, Nanjing 210018, China 
CAO Lei Geological Survey of Jiangsu Province, Nanjing 210018, China 
CAO Jing-yang Geological Survey of Jiangsu Province, Nanjing 210018, China 
LU Xin-cheng Geological Survey of Jiangsu Province, Nanjing 210018, China 
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Abstract:
      BACKGROUND: Soil limit water content is an important basis for fine-grained soil classification and engineering property evaluation. Additionally, it is an important evaluation index for clay exploration and industrial utilization. Inaccurate test results of soil limit water content may lead to serious engineering safety accidents and personal and economic property losses. Certified reference materials (CRMs) are important for ensuring the accuracy, comparability, and effectiveness of the analyzed data. However, no certified reference materials for soil limit water content exist; therefore, the preparation of CRMs for the soil limit water content holds great significance.
OBJECTIVES: To prepare CRMs of soil limit water content.
METHODS: In strict accordance with the specifications and standards, such as "Technical Specifications for First-Class Reference Materials" (JJF 1006-1994) and "General Principles and Statistical Principles for the Valuation of Reference Materials" (JJF 1343-2012), five standard materials of soil limit water content (GBW07969, GBW07970, GBW07971, GBW07972, and GBW07973) have been developed. These samples were collected from Huaibei of Anhui province, Datong of Shanxi province, and Nanjing of Jiangsu province. After artificial crushing, drying, and sterilization, the samples were finely crushed to less than 0.25mm by a large ball mill. After particle size analysis, the samples were bottled and numbered in a clean room.
RESULTS: Twenty-five bottles of each sample were randomly selected for homogeneity testing. All the measured values of F were less than F0.05 (24, 25)=1.96, and the relative standard deviation (RSD) was between 1.16% and 2.67%, which indicated good uniformity. There were no significant differences in the long-term stability test (12months) and the short-term stability test (60℃, -20℃). The certified values of 10mm liquid limit, plastic limit, and plasticity index were 26.3%-39.9%, 16.9%-22.2%, and 10.0%-17.7%, respectively. The gradient series was significant, which included silty clayey and clayey type of soils.
CONCLUSIONS: Five first classes of National CRMs (GBW07969, GBW07970, GBW07971, GBW07972, and GBW07973) of soil limit water content were successfully prepared. This series of CRMs can be used for calibration of instruments and equipment, quality control, capability verification, and other technical quality activities, which provide a guarantee for the accuracy requirements of soil limit water test data in hydraulic environment geological exploration, geotechnical engineering exploration, clay mine exploration, and other related disciplines.