Once an initial design for the vacuum mould was complete, a prototype mould was manufactured and tested within GDS. This was assessed as part of other work investigating the response of granular soil when cyclically sheared under constant volume conditions (i.e., constant height) in the GDS EMDCSS, which is an NGI-style direct simple shear system. During specimen preparation the vacuum mould was found to work as per the design, holding the membrane tightly against the confining rings while Toyoura sand was deposited. A series of four Toyoura sand samples were cyclically sheared under constant volume conditions (i.e., constant height) to ensure the performance of the specimens prepared with the vacuum former was as expected. The data from these four tests was then compared with four sets of data from hollow cylinder (HC) apparatus testing. This data will be presented in GDS' April news.
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