Sample Size Effects Using the NGI (Norwegian Geotechnical Institute) Direct Simple Shear Apparatus

摘要

To improve the use and the interpretation of results of the Norwegian Geotechnical Institute (NGI) direct simple shear device modified for cyclic loading, tests were conducted using undisturbed soil samples of Gulf of Alaska and Gulf of Mexico clays. The effects of variations in sample size are quantified. The parameters which varied were sample cross section and sample height. Two cross-sectional sizes and three heights were compared. Equipment used in the investigation, testing procedures, and soil characteristics are discussed. Test data include lateral strain measurements from which horizontal normal stresses and subsequently the initial lateral stress ratio values were calculated. These calcultions and results are discussed as affected by sample size, with special attention to the initial lateral stress ratio. Step-by-step instructions on the use of the use of the NGI direct simple shear device in both static and cyclic functions are explained. The use of the NGI sample trimming apparatus and methods for calibrating the NGI reinforced membrances using calibration cylinders are detailed.