Closure to “New Model for Predicting Permanent Strain of Granular Materials in Embankment Subjected to Low Cyclic Loadings” by Wen-Bo Chen, Wei-Qiang Feng, Jian-Hua Yin, Jin-Miao Chen, Lalit Borana, and Ren-Peng Chen

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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Permanent Strain of Unsaturated Unbound Granular Materials from Construction and Demolition Waste

Journal of Materials in Civil Engineering ◽

10.1061/(asce)mt.1943-5533.0001052 ◽

2015 ◽

Vol 27 (3) ◽

pp. 04014125 ◽

Cited By ~ 22

Author(s):

A. M. Azam ◽

D. A. Cameron ◽

M. M. Rahman

Keyword(s):

Granular Materials ◽

Construction And Demolition Waste ◽

Demolition Waste ◽

Permanent Strain ◽

Unbound Granular Materials

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Permanent Strain Behavior of Marginal Granular Material

Transportation Research Record Journal of the Transportation Research Board ◽

10.3141/2655-08 ◽

2017 ◽

Vol 2655 (1) ◽

pp. 54-63 ◽

Cited By ~ 5

Author(s):

Wentao Li ◽

Douglas J. Wilson ◽

Tam J. Larkin ◽

Philippa M. Black

Keyword(s):

Strain Rate ◽

Granular Materials ◽

Permanent Deformation ◽

High Stress ◽

Repeated Loading ◽

Swelling Clay ◽

One Dimensional ◽

Permanent Strain ◽

Strain Behavior ◽

Swelling Clay Minerals

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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