Near-surface soils: discrete element modeling of self-supported unconfined drained sand specimens

Allen, Jeffrey; Taylor, O. C.

doi:10.1007/s12572-020-00275-5

Cited by 1 publication

(2 citation statements)

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“…The MD and GTD holistic models produced a prediction for failure conditions and internal instabilities that was then validated against silty sand (SM) and engineered soil (EngMix). At the mesoscopic (granular) scale, there exists an interdependency of ICP between the state variables of the granular structure and the pore fluid that defines macroscopic behavior [34], Fig. 4.…”

Section: Sigmoid Saturation Modelsmentioning

confidence: 99%

“…Prevailing models of near-surface soil behavior are based on research executed in confined tests over uniform saturation, where soil is represented as a collection of interacting individual grains and not idealized homogeneous visco-elastic media [13]. Particle size, shape, and polydispersity determine the granular contact area [14][15][16][17][18][19][20]; bulk soil density and anisotropy define a soil's skeletal structure and interaction of the internal force chains [21][22][23][24][25][26][27][28][29][30][31][32][33][34]. In contrast, the energy balance theory of granular behavior presented here is based on variably saturated data from 30 soil water retention curves (SWRC), 360 ultrasonic near-surface inundation tests (UNITs), and 97 unconstrained (free-standing) tests using three different materials (Data S1-S3).…”

Section: Introductionmentioning

confidence: 99%

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To fall or not to fall: the physics of sandcastles

2021

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Understanding how porous structures become rigid and retain their strength or fail over variable saturation rates is crucial for designing materials with targeted performances under different processing conditions. This is especially true for the development of materials with time-dependent viscosities (i.e., thixotropic or rheopectic materials) and the emerging science behind manipulatable advanced geometamaterials. Nowhere are these issues more ubiquitous than in the physics of sandcastles. Modeling unconstrained granular columns traversing the microscale (granular temperature) to the mesoscale (internal granular force chains and interactions with pore fluid) and defining the macroscale properties, characteristics and behaviors are key to the development of a universal picture. Herein, we experimentally investigate how an unconstrained granular column can retain structure over a range of saturations. Analyzing a suite of 487 macroscale tests, sigmoid saturation models were developed that define state variable interactions within the mesoscale mechanical domain. This led to the formulation of an energy balance model based on microscale interactions via a 1D thermostatistical picture applied to the granular temperature. The difference between strength and stability can thus be independently observed simultaneously. The two domains are not necessarily synonymous (i.e., strong may not be stable), and the energy cost to change the stability state on the microscopic scale becomes a quantifiable physical property that manifests in macroscopic granular behavior.

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Section: Sigmoid Saturation Modelsmentioning

confidence: 99%