Properties of granular analogue model materials: A community wide survey

Abstract

12 13We report the material properties of 26 granular analogue materials used in 14 ana-14 logue modelling laboratories. We determined physical characteristics such as bulk 15 density, grain size distribution, and grain shape, and performed ring shear tests to 16 determine friction angles and cohesion, and uniaxial compression tests to evaluate 17 the compaction behaviour. Mean grain size of the materials varied between c. 100 18 and 400 µm. Analysis of grain shape factors show that the four different classes of 19 granular materials (14 quartz sands, 5 dyed quartz sands, 4 heavy mineral sands 20 and 3 size fractions of glass beads) can be broadly divided into two groups consist-21 ing of 12 angular and 14 rounded materials. Grain shape has an influence on friction 22 angles, with most angular materials having higher internal friction angles (between 23 c. 35° and 40°) than rounded materials, whereas well-rounded glass beads have the 24 lowest internal friction angles (between c. 25° and 30°). We interpret this as an ef-25 2 fect of intergranular sliding versus rolling. Most angular materials have also higher 26 basal friction angles (tested for a specific foil) than more rounded materials, sug-27 gesting that angular grains scratch and wear the foil., Most materials have an inter-28 nal cohesion in the order of 20-100 Pa except for well-rounded glass beads, which 29show a trend towards a quasi-cohesionless (C <20 Pa) Coulomb-type material. The 30 uniaxial confined compression tests reveal that rounded grains generally show less 31 compaction than angular grains. We interpret this to be related to the initial packing 32 density after sifting, which is higher for rounded grains than for angular grains. Ring-33 shear test data show that angular grains undergo a longer strain-hardening phase 34 than more rounded materials. This might explain why analogue models consisting of 35 angular grains accommodate deformation in a more distributed manner prior to 36 strain localisation than models consisting of rounded grains.

Analogue earthquakes and seismic cycles: experimental modelling across timescales

“…2c) to study ground motion have been followed by a number of similar studies which helped in interpreting seismological observations and improving numerical predictions. King and Brune (1981) summarized the modelling approach by stating that "The foam model acts as an analogue computer that automatically accounts for the diffraction, refraction, reflection, and conversion phenomena that occur when seismic waves interact with an attenuative, linear-elastic soil structure". Foam rubber models were for example amongst the first to explain the strong asymmetry in particle motion and associated ground motion across dipping faults.…”

“…A co-genetic though more engineering-type approach has been used to study site effects due to topography (Anooshehpoor and Brune, 1989), sedimentary basins (King and Brune, 1981), and the response of buildings and other structures, such as dams, to earthquakes (e.g. Brune and Anooshehpoor, 1991a;Anooshehpoor and Brune, 1989).…”

Control of Fault Weakening on the Structural Styles of Underthrusting‐Dominated Non‐Cohesive Accretionary Wedges

“…Analog sandbox experiments have been used extensively to study the dynamics of accretionary prisms (for recent reviews, see Buiter, ; Graveleau et al, ; Schreurs et al, ). Sandbox experiments are often performed in subaerial (dry) conditions, that is, , and the sands used in experiments are estimated to have a weakening factor if the difference between peak and reactivation friction coefficient is considered, or if instead the difference between peak and dynamic friction coefficient is considered (Klinkmüller et al, ) (Figure ). Therefore, our results predict that sandbox experiments should feature Styles 1 to 2 for .…”

How the presence of a salt décollement in the sedimentary cover influences the behavior of subsalt thrusts in fold-and-thrust belts

“…Here, we present only the three most significant ones. All models were made mostly of dry quartz sand (angle of internal friction: 30-34°) (Klinkmüller et al, 2016) and had an initial length of 121 cm, and an initial total thickness of 28 mm (lower and upper series) resting on a 2 mm thick layer of glass microbeads, which acted as a deep frictional basal detachment (Fig. 2).…”