Influence of spherical voids on the unconfined compressive strength of plaster cylinders: Comparison of models & lab data

To study the influence of large voids on the unconfined compressive strength (UCS) of brittle materials, fifty-four 3″ by 6″ cylindrical plaster specimens were created. The specimens contained 1″ diameter spherical Styrofoam inclusions, which represent the large voids, with the inclusions placed in either structured or random locations. Each specimen contained between 1 and 24 inclusions. After laboratory testing, the specimens were dissected to determine the precise location of the inclusions. A FLAC3D numerical model was then created for each specimen and the UCS was determined using numerical simulation. To date, 17 specimens have been tested in the laboratory, and 12 numerical models have been completed. The UCS _laboratory values are almost always lower than the UCS _numerical values; on average 15% lower than the UCS _numerical values. This is expected because the laboratory specimens contain defects such as trapped air pockets which are not accounted for in the numerical simulations. The new results, both numerical and experimental, are within the range of data previously collected.