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

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).

本数据集提供了用于比利时布鲁塞尔自由大学（Vrije Universiteit Brussel）地理系模拟实验室模拟上地壳脆性岩石的力学测试数据，受试材料包括石英砂（"MAM1ST-300"，Sibelco，比利时莫尔）、石膏粉（抹灰石膏；"Goldband"，Knauf，可耐福）、高岭土粉、石榴石砂，以及石英砂与石膏粉的混合体系（Poppe等，2019）。所测得的物性参数包括密度ρ、抗拉强度T₀与抗剪强度σ。其中密度通过密度测量法获得，抗剪强度则分别通过环剪试验（RST，德国波茨坦亥姆霍兹中心GFZ）、直剪试验、牵引试验（法国勒芒缅因大学）以及拉伸试验测得。所得抗拉强度与抗剪强度可构建每种受试材料的二维破坏包络线。通过将线性库仑（Coulomb）破坏准则与非线性组合格里菲斯（Griffith）破坏准则拟合至表征得到的破坏包络线（Jaeger等，2007），可求得内摩擦系数μ_C、库仑黏聚力C_C以及格里菲斯黏聚力C_G。Poppe等（2021）曾针对材料置样工艺的影响展开研究，本数据集为该研究的补充数据：通过在三种置样条件下重复表征上述物理参数，即筛分法、浇筑法（未干燥状态）以及浇筑后压实法（烘箱干燥状态），系统探究了置样工艺对材料物性的影响。研究结果显示，各类材料及混合体系的密度范围如下：纯石英砂的密度约为1600 kg·m⁻³（筛分法）至1700 kg·m⁻³（压实法），纯石膏的密度范围约为600 kg·m⁻³（浇筑法）至900 kg·m⁻³（压实法）。抗拉强度范围约为166 Pa（石英砂）至425 Pa（石膏）。对90 wt%石英砂-10 wt%石膏混合体系开展的环剪速度试验表明，剪切速率每提升一个数量级，剪切弱化幅度小于2%。受试材料的破坏行为呈现连续谱分布：粗颗粒材料（砂类）表现为莫尔-库仑（Mohr-Coulomb）破坏行为，粉末类材料（石膏、高岭土）则表现为格里菲斯-莫尔-库仑组合破坏行为，而砂-石膏混合体系的破坏行为介于两种极端类型之间。峰值摩擦系数范围约为0.5（石英砂）至0.6（石膏），其中80:20质量比的砂:石膏混合体系峰值摩擦系数可达约0.9；峰值库仑黏聚力范围为13 Pa（石英砂）至248 Pa（石膏）；峰值格里菲斯黏聚力范围约为10 Pa（石英砂）至425 Pa（石膏）。