ESTIMATION OF SAMPLING QUALITY FOR SIEVE ANALYSIS OF SANDY AND GRAVELLY SAMPLES—DISCUSSION ON CURRENT NATIONAL STANDARDS
Sieve analysis is an analytical technique widely used for measuring particle sizes of detrital sediments,characterized by low hardware requirements,simple operation,and broad applicability.For sandy-gravelly sediments,in specific particle size analysis experiments,there is currently a lack of comprehensive and scientifically defined technical specifications regarding the appropriate quantity for grain-size analysis.Part 8 of the"Specifications for Marine Surveys:Marine Geological and Geophysical Surveys"(China's national standard #GB/T 12763.8-2007)offers partial solutions to this issue,but its principles are unclear and it does not cover comprehensively the particle size range of conglomerate sediments.We conducted this study to analyze and discuss the estimation of grain-size analysis.Based on probability distribution theory,a set of formulas for grain-size analysis quantity estimation from sandy-gravelly samples was derived for sieve analysis.Furthermore,the theoretical minimum sampling range corresponding to the maximum particle diameter of the sample under different sorting coefficients(0.35 Φ～4.00 Φ)was obtained.The quantitative relationship between the maximum particle diameter and the minimum sampling quantity in the national standard we currently followed in marine survey may be derived based on the normal distribution and the sorting coefficient of 4.00 Φ.The maximum particle diameter in the sieve analysis sampling quality estimation table can be extended to 64 mm,and the theoretical minimum sampling quantity corresponding to this particle size is 47.8 kg.To verify the derived formula,taking nearly 200 sand and gravel samples from the intertidal zone of Zhoushan Islands and Xiangshan Peninsula in Zhejiang Province as examples,the theoretical minimum sampling quantity and ideal normal particle size distribution of sieve analysis method corresponding to the maximum particle diameter of the samples were calculated,and compared with the actual sampling quantity and particle size distribution analysis results.The results show that the particle size analysis results of most samples approximated a normal distribution,and the correlation between the theoretically derived sampling quantity and the actual sampling quantity was relatively ideal.The above-mentioned works can provide reference for the revision of current marine survey standards.
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