Mechanical test data of quartz sand, garnet sand, gypsum powder (plaster), kaolin and sand-plaster mixtures used as granular analogue materials in geoscience laboratory experiments

Abstract

This dataset provides mechanical test data for quartz sand (“MAM1ST-300”, Sibelco, Mol, Belgium), gypsum powder (plaster; “Goldband”, Knauf), kaolin clay powder, garnet sand, and mixtures of quartz sand and gypsum powder, used at the Analogue Laboratory of the Department of Geography at the Vrije Universiteit Brussel, Brussels, Belgium, for simulating brittle rocks in the upper crust (Poppe et al., 2019). The measured properties are density ρ, tensile strength T0, shear strength σ, obtained by density measurements, ring-shear tests (RST; at Helmholtz Centre Potsdam GFZ, Germany), direct shear tests, traction tests (at University of Maine, Le Mans, France) and extension tests. The obtained tensile strengths and shear strengths reconstruct two-dimensional failure envelopes for each material. By fitting linear Coulomb and non-linear combined Griffith failure criteria to the characterised failure envelopes (Jaeger et al., 2007), the internal friction coefficient µC, Coulomb cohesion CC and Griffith cohesion CG are obtained. The influence of the material emplacement technique has been investigated in Poppe et al. (2021) to which this data set is supplementary, by repeat characterisation of the above physical parameters under three emplacement conditions, i.e. sieving, pouring (non-dried state) and compaction after pouring (oven-dried state). We find that densities of the materials and mixtures range from ~1600 kg.m³ (sieved) and ~1700 kg.m³ (compacted) for pure quartz sand to ~600 kg.m³ (poured) to ~900 kg.m³ (compacted) for pure plaster. Tensile strengths range from ~166 Pa (sand) to ~425 Pa (plaster). Velocity ring-shear tests on a 90 wt% quartz sand – 10 wt% plaster mixture show a minor shear rate-weakening of <2% per ten-fold increase in shear velocity. The materials show a behavior ranging from Mohr-Coulomb behavior for the materials with coarser grain size (sands) to combined Griffith-Mohr-Coulomb behavior for the powder materials (plaster, kaolin), with the sand-plaster mixtures occupying a spectrum between both end-members. Peak friction coefficients range from ~0.5 (sand) to ~0.6 (plaster) with a maximum of ~0.9 (80:20 wt% sand:plaster), peak Coulomb cohesions range from 13 Pa (sand) to 248 Pa (plaster), peak Griffith cohesions range from ~10 Pa (sand) to ~425 Pa (plaster).