Unconfined compressive strength of 4-inch plaster cubes containing large voids

摘要

The presence of large voids ("macroporosity") can have a large influence on the engineering properties of materials, but quantifying this influence is not a simple undertaking due to the variation in void size, shape, and spacing. In a recent Montana Tech master's thesis, the influence of void spacing was investigated using 4" cubic specimens containing seven 0.5" diameter cylindrical voids oriented in a cluster around the center of the specimens. Numerical and experimental results suggest that void spacing has significant influence on unconfined compressive strength (UCS); the controlling factor appears to be the width of the solid "pillars" that are able to carry load. The work described in this paper is an expansion of the earlier study, in which some of the voids in the cluster are not present. Sixty two-dimensional FLAC numerical models containing three and five 0.5" diameter voids produced evidence supporting the interpretation that "pillar" size controls the specimen UCS: in all cases except one, the UCS values of the three and five void configurations were moderately to significantly different from those with the seven-void cluster only when the pillar size was substantially increased. Twenty-five specimens were tested in the laboratory to verify the results of the numerical models.