Permanent Strain Behavior of Marginal Granular Material

To better understand the marginality of marginal granular materials (i.e., an aggregate that does not fully meet a premium quality specification), this study investigated the permanent strain behavior of two granular materials with different geological and mineralogical characteristics under repeated loading and different moisture conditions. The secant permanent strain rate and shakedown approach were used to analyze the permanent strain behavior of the materials. A one-dimensional swelling test was used to explain the mechanism of the permanent strain behavior of the soaked materials under repeated loading. The results show that compared with a New Zealand premium quality aggregate, the marginal aggregate exhibits a more significant increase in the cumulative permanent strain and the secant permanent strain rate after the 4-day soaking process. The results of the shakedown approach illustrate that the marginal aggregate performs reasonably well to resist permanent deformation in a dry condition, but the performance will considerably deteriorate when in contact with water under high stress. This change is a result of the presence of swelling clay minerals (e.g., smectite) in the marginal aggregates. The result of the one-dimensional swelling test indicates the high swelling potential of marginal aggregate, which provides an explanation for its poorer resistance to permanent strain. The marginal aggregate gains undesirable internal lubrication when surrounded by (moist) swelling clay mineral particles; thus, its shear strength reduces and permanent strain rate increases under repeated loading.

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Influences on Permanent Deformation Behavior of Unbound Granular Materials

Transportation Research Record Journal of the Transportation Research Board ◽

10.1177/0361198196154700110 ◽

1996 ◽

Vol 1547 (1) ◽

pp. 68-75 ◽

Cited By ~ 13

Author(s):

Fredrick Lekarp ◽

Ian Reginald Richardson ◽

Andrew Dawson

Keyword(s):

Granular Materials ◽

Stress Level ◽

Deformation Behavior ◽

Permanent Deformation ◽

Repeated Loading ◽

Permanent Strain ◽

Unbound Granular Materials ◽

Failure Line ◽

Static Failure ◽

French Model

The results of a research program aimed at characterizing the permanent deformation behaviors of different types of unbound aggregates under repeated loading are summarized. Tests were performed in a triaxial or hollow-cylinder apparatus, depending on the grading of the materials. The scope of the research was to assess the relationship between total permanent axial strain and both the number of load applications and the stress level. The test results were used to verify a model recently developed in France in which attempts are made to predict the long-term behaviors of granular materials. The French model is examined with particular reference to its validity on the effect of stress level on permanent deformation of unbound granular materials. The results of the study indicate that the French model is generally successful in predicting the permanent strain for a given number of load applications. For one of the materials, however, the model did not seem to fit the data well. The French model also suggests that the variation in total permanent strain with stress level is related to the static failure line and could be determined by comparing the maximum shear stress ratio with the slope of the estimated failure line. This is discussed and shown to be questionable because it results in either unreasonable failure parameters or a very low level of correlation with the observations. An attempt was made to modify the French model, but that also proved to be unsuccessful. The concept of relating the permanent deformation behavior to the static failure condition of the material is therefore questioned.

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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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Mitigation of permanent deformation in base layer containing recycled asphalt aggregates

Canadian Journal of Civil Engineering ◽

10.1139/cjce-2012-0395 ◽

2013 ◽

Vol 40 (2) ◽

pp. 181-187 ◽

Cited By ~ 6

Author(s):

Jean-Pascal Bilodeau ◽

Guy Doré ◽

Jonas Depatie

Keyword(s):

Asphalt Concrete ◽

Deformation Behaviour ◽

Permanent Deformation ◽

Design Procedure ◽

Base Layer ◽

Repeated Loading ◽

Recycled Asphalt ◽

Thickness Increase ◽

Permanent Strain ◽

Pavement Base

The use of recycled asphalt pavement (RAP) aggregates as replacement for new materials in the pavement base weakens the layer in regards to the resistance to permanent deformation under repeated loading. A mechanistic based design procedure is proposed to ensure that base layers containing RAP particles have a similar rutting behaviour to base layers made of virgin aggregates. The design procedure allows calculating an asphalt concrete thickness increase that is based on permanent deformation behaviour of base materials. The calculation approach is based on multistage triaxial permanent deformation tests performed on granular material samples with varied RAP content. The tests allowed proposing an equation that relates permanent strain rate, RAP content, and deviatoric stress, which is the basis of the design procedure. Design charts are proposed to select adequate thickness increase for the asphalt concrete layer according to the expected RAP content in the base layer and asphalt concrete modulus.

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Numerical study of one-dimensional compression of granular materials. I. Stress-strain behavior, microstructure, and irreversibility

Physical Review E ◽

10.1103/physreve.95.032907 ◽

2017 ◽

Vol 95 (3) ◽

Cited By ~ 15

Author(s):

Mohamed Hassan Khalili ◽

Jean-Noël Roux ◽

Jean-Michel Pereira ◽

Sébastien Brisard ◽

Michel Bornert

Keyword(s):

Granular Materials ◽

Numerical Study ◽

Stress Strain ◽

One Dimensional ◽

Strain Behavior

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Experimental study on permanent deformation characteristics of coarse-grained soil under repeated dynamic loading

Railway Engineering Science ◽

10.1007/s40534-021-00233-2 ◽

2021 ◽

Author(s):

Huihao Mei ◽

Sajjad Satvati ◽

Wuming Leng

Keyword(s):

Stress State ◽

Strain Rate ◽

Dynamic Stress ◽

Stress Amplitude ◽

Permanent Deformation ◽

Confining Pressure ◽

Coarse Grained ◽

Deformation Characteristics ◽

Permanent Strain ◽

Coarse Grained Soil

AbstractPractical assessment of subgrade settlement induced by train operation requires developing suitable models capable of describing permanent deformation characteristics of subgrade filling under repeated dynamic loading. In this paper, repeated load triaxial tests were performed on coarse-grained soil (CGS), and the axial permanent strain of CGS under different confining pressures and dynamic stress amplitudes was analysed. Permanent deformation behaviors of CGS were categorized based on the variation trend of permanent strain rate with accumulated permanent strain and the shakedown theory. A prediction model of permanent deformation considering stress state and number of load cycles was established, and the ranges of parameters for different types of dynamic behaviors were also divided. The results indicated that the variational trend of permanent strain rate with accumulated permanent strain can be used as a basis for classifying dynamic behaviors of CGS. The stress state (confining pressure and dynamic stress amplitude) has significant effects on the permanent strain rate. The accumulative characteristics of permanent deformation of CGS with the number of load cycles can be described by a power function, and the model parameters can reflect the influence of confining pressure and dynamic stress amplitude. The study’s results could help deepen understanding of the permanent deformation characteristics of CGS.

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