Exploring soil mechanics laboratory tests: accuracy, discrepancies, and implications

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Publication Title
Exploring soil mechanics laboratory tests: accuracy, discrepancies, and implications

Abstract
In this paper, a summary of the study on the accuracy of routine soil mechanics laboratory tests and their implications for engineering geologists is presented. The shear strength and physical properties of soils, all material parameters, which should yield consistent results across different laboratories for a given soil were examined. The accuracy of laboratory test results can be influenced by various factors, including the thoroughness of reconstituted slurry preparation, the choice of the apparatus or test method, or discrepancies in the processing of tests by the laboratory itself. To investigate this issue, several samples of fine-grained soils were submitted to 3 different soil mechanics laboratories. The findings revealed significant discrepancies in the results obtained. For instance, the determination of the clay fraction through grain size distribution exhibited differences of up to 43% between two laboratories (22% versus 65%). Similarly, significant variations were observed in the determination of shear strength parameters, where the critical friction angle differed by 8° on a single soil (20.5° versus 28.5°). These discrepancies have practical implications, particularly when considering numerical modelling of slope stability what can lead to unrealistic conclusions. This was demonstrated through a parametric study of a model landslide, which yields varying results for the factor of safety between 1 to almost 3. Overall, this study emphasizes the importance of accurate and consistent laboratory test results in soil mechanics across different laboratories. By addressing the factors influencing accuracy increases the reliability and practical implications of soil mechanics testing. Furthermore, given the inconsistencies in the results, the utility of correlation equations as a valuable tool for estimating shear strength of soils is demonstrated.
Author
J. Rohac

Published In

18th European Conference on Soil Mechanics and Geotechnical Engineering (ECSMGE2024)

Theme

C - Risk analysis and safety evaluation

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