THE APPLICATION OF WEIBULL STATISTICS TO THE FRACTURE OF SOIL PARTICLES

G.R.MCDOWELL and A.AMON

ABSTRACT: This paper presents an analysis of Weibull statistics applied to tensile failure of soil grains compressed between flat platens. The aim is to validate the use of Weibull applied to single soil grains, since such a statistical approach can then be used to analyse particle survival in aggregates comprising many soil particles. Particles of Quiou sand have been compressed diametrically between flat platens. A characteristic stress at failure can be defined as the diametral force divided by the square of the particle diameter at failure. Approximately 30 grains were tested for each of the following nominal particle sizes: 1 mm, 2 mm, 4 mm, 8 mm and 16 mm diameter. It was found that the data could be well described by the Weibull statistics of brittle ceramics, which requires an assumption of geometric similarity to be made, and the Weibull modulus could be taken to be about 1.5. This is shown to be in agreement with the observation that the average crushing force is not a strong function of particle size. The force required to break a small particle asperity is also shown not to be a strong function of the asperity size, consistent with the observed Weibull modulus. The paper provides evidence that Weibull can reasonably be applied to the tensile failure of soil grains, thus validating the use of Weibull as a tool in the analysis of particle crushing.

Key words: micro mechanics, particle crushing, sands, statistical analysis, strength (IGC: D/6)