Statistical Modelling of the Resilient Behaviour of Unbound Granular Material

Abstract The resilient behaviour of an unsaturated, unbound granular material is a primary input used in the mechanistic analysis of pavements incorporating such layers. Various models exist for the determination of the resilient behaviour, mainly based on the output of tri-axial laboratory testing. This paper describes an investigation where basic engineering properties such as grading, laboratory compaction characteristics and optimum moisture content are incorporated into the resilient behaviour model to quantify the effect of basic material properties on the resilient response of unsaturated, unbound granular materials. Such a resilient behaviour model will enable practitioners to estimate the behaviour of specific material, which might enable the use of available quality material that was discarded in the past. Data from tri-axial laboratory tests on materials originating from the Long Term Pavement Performance test sections are combined with basic engineering parameters of typical unbound granular material through a statistical modelling process to develop a model for predicting resilient behaviour, which can be used as a practical predictor of the expected behaviour during a Level 2 and/or Level 3 Mechanistic Empirical Pavement Design analysis. The work illustrates the process and the potential to develop a general resilient behaviour model for unbound granular materials incorporating saturation effects.

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The effect of weathering on the engineering properties of laboratory compacted unbound granular materials (UGMs)

Construction and Building Materials ◽

10.1016/j.conbuildmat.2021.122242 ◽

2021 ◽

Vol 276 ◽

pp. 122242

Author(s):

Ebrahim Sangsefidi ◽

Tam Joseph Larkin ◽

Doug James Wilson

Keyword(s):

Granular Materials ◽

Engineering Properties ◽

Unbound Granular Materials

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Simulation of Permanent Deformation of Unbound Granular Materials Under Repeated Loading by DEM

Procedia - Social and Behavioral Sciences ◽

10.1016/j.sbspro.2013.08.059 ◽

2013 ◽

Vol 96 ◽

pp. 505-511

Author(s):

Xiao Zhang

Keyword(s):

Granular Materials ◽

Permanent Deformation ◽

Repeated Loading ◽

Unbound Granular Materials

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A frictional Cosserat model for the slow shearing of granular materials

Journal of Fluid Mechanics ◽

10.1017/s0022112002007796 ◽

2002 ◽

Vol 457 ◽

pp. 377-409 ◽

Cited By ~ 71

Author(s):

L. SRINIVASA MOHAN ◽

K. KESAVA RAO ◽

PRABHU R. NOTT

Keyword(s):

Angular Velocity ◽

Granular Material ◽

Shear Layer ◽

Granular Materials ◽

Layer Thickness ◽

Couette Flow ◽

Velocity Fields ◽

Cosserat Continuum ◽

Cosserat Model ◽

Cylindrical Couette Flow

A rigid-plastic Cosserat model for slow frictional flow of granular materials, proposed by us in an earlier paper, has been used to analyse plane and cylindrical Couette flow. In this model, the hydrodynamic fields of a classical continuum are supplemented by the couple stress and the intrinsic angular velocity fields. The balance of angular momentum, which is satisfied implicitly in a classical continuum, must be enforced in a Cosserat continuum. As a result, the stress tensor could be asymmetric, and the angular velocity of a material point may differ from half the local vorticity. An important consequence of treating the granular medium as a Cosserat continuum is that it incorporates a material length scale in the model, which is absent in frictional models based on a classical continuum. Further, the Cosserat model allows determination of the velocity fields uniquely in viscometric flows, in contrast to classical frictional models. Experiments on viscometric flows of dense, slowly deforming granular materials indicate that shear is confined to a narrow region, usually a few grain diameters thick, while the remaining material is largely undeformed. This feature is captured by the present model, and the velocity profile predicted for cylindrical Couette flow is in good agreement with reported data. When the walls of the Couette cell are smoother than the granular material, the model predicts that the shear layer thickness is independent of the Couette gap H when the latter is large compared to the grain diameter dp. When the walls are of the same roughness as the granular material, the model predicts that the shear layer thickness varies as (H/dp)1/3 (in the limit H/dp [Gt ] 1) for plane shear under gravity and cylindrical Couette flow.

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