Permanent deformation testing for a new South African mechanistic pavement design method

2012 ◽  
Vol 26 (1) ◽  
pp. 541-546 ◽  
Author(s):  
Joseph Anochie-Boateng ◽  
James Maina
Keyword(s):  
South African ◽  
Design Method ◽  
New South ◽  
Permanent Deformation ◽  
Pavement Design

Design of Granular Pavements

2003 ◽  
Vol 1819 (1) ◽  
pp. 194-200 ◽  
Author(s):  
Greg Arnold ◽  
David Hughes ◽  
Andrew R. Dawson ◽  
Des Robinson
Keyword(s):  
Stress State ◽  
Design Method ◽  
Permanent Deformation ◽  
Design Criterion ◽  
Pavement Design ◽  
Performance Criteria ◽  
Crushed Rock ◽  
Long Distance ◽  
High Quality ◽  
Final Thickness

The use of high-quality quarried crushed rock aggregates is generally required to comply with current specifications for unbound granular materials (UGMs) in pavements. The source of these high-quality materials can be a long distance from the site, resulting in high transportation costs. The use of more local sources of marginal materials or the use of secondary aggregates is not allowed if they do not fully comply with existing specifications. These materials can, however, be assessed for their suitability for use in a pavement by considering performance criteria such as resistance to permanent deformation and degradation instead of relying on compliance with inflexible specifications. The final thickness of the asphalt cover and the pavement depth are governed by conventional pavement design methods, which consider the number of vehicle passes, subgrade strength, and some material property, commonly the California bearing ratio or resilient modulus. A pavement design method that includes as a design criterion an assessment of the resistance to deformation of a UGM in a pavement structure at a particular stress state is proposed. The particular stress state at which the aggregate is to perform in an acceptable way is related to the in situ stress, that is, the stress that the aggregate is anticipated to experience at a particular depth in the pavement. Because the stresses are more severe closer to the pavement surface, the aggregates should be better able to resist these stresses the closer they are laid to the surface in the pavement. This method was applied to two Northern Ireland aggregates of different quality (NI Good and NI Poor). The results showed that the NI Poor aggregate performed at an acceptable level with respect to permanent deformation, provided that a minimum of 70 mm of asphalt cover was provided. It was predicted that the NI Good material would require 60 mm of asphalt cover.

Overview of South African Mechanistic Pavement Design Method

1996 ◽  
Vol 1539 (1) ◽  
pp. 6-17 ◽  
Author(s):  
H. L. Theyse ◽  
M. De Beer ◽  
F. C. Rust
Keyword(s):  
Structural Analysis ◽  
South African ◽  
Material Characterization ◽  
Life Prediction ◽  
Transfer Functions ◽  
Design Method ◽  
Pavement Design ◽  
Critical Parameters ◽  
Historical Overview ◽  
Modes Of Failure

A historical overview of the South African mechanistic pavement design method, from its development in the early 1970s to the present, is presented. Material characterization, structural analysis, and pavement life prediction are discussed, and stiffness values are suggested for a range of materials in the absence of measured values. The modes of failure for these material types include the fatigue of asphalt material, deformation of granular material, crushing and effective fatigue of lightly cemented material, and deformation of selected and subgrade material. The critical parameters and transfer functions for these material types and modes of failure are discussed and included in the pavement life prediction process.

scholarly journals Structural Evaluation of Full-Depth Flexible Pavement Using APT

2021 ◽  
Author(s):  
Tommy E. Nantung ◽  
Jusang Lee ◽  
John E. Haddock ◽  
M. Reza Pouranian ◽  
Dario Batioja Alvarez ◽  
...  
Keyword(s):  
Asphalt Concrete ◽  
Prediction Models ◽  
Design Method ◽  
Permanent Deformation ◽  
Pavement Design ◽  
Asphalt Pavements ◽  
Statistical Parameters ◽  
Significant Difference ◽  
Pavement Structures ◽  
Rutting Behavior

The fundamentals of rutting behavior for thin full-depth flexible pavements (i.e., asphalt thickness less than 12 inches) are investigated in this study. The scope incorporates an experimental study using full-scale Accelerated Pavement Tests (APTs) to monitor the evolution of each pavement structural layer's transverse profiles. The findings were then employed to verify the local rutting model coefficients used in the current pavement design method, the Mechanistic-Empirical Pavement Design Guide (MEPDG). Four APT sections were constructed using two thin typical pavement structures (seven-and ten-inches thick) and two types of surface course material (dense-graded and SMA). A mid-depth rut monitoring and automated laser profile systems were designed to reconstruct the transverse profiles at each pavement layer interface throughout the process of accelerated pavement deterioration that is produced during the APT. The contributions of each pavement structural layer to rutting and the evolution of layer deformation were derived. This study found that the permanent deformation within full-depth asphalt concrete significantly depends upon the pavement thickness. However, once the pavement reaches sufficient thickness (more than 12.5 inches), increasing the thickness does not significantly affect the permanent deformation. Additionally, for thin full-depth asphalt pavements with a dense-graded Hot Mix Asphalt (HMA) surface course, most pavement rutting is caused by the deformation of the asphalt concrete, with about half the rutting amount observed within the top four inches of the pavement layers. However, for thin full-depth asphalt pavements with an SMA surface course, most pavement rutting comes from the closet sublayer to the surface, i.e., the intermediate layer. The accuracy of the MEPDG’s prediction models for thin full-depth asphalt pavement was evaluated using some statistical parameters, including bias, the sum of squared error, and the standard error of estimates between the predicted and actual measurements. Based on the statistical analysis (at the 95% confidence level), no significant difference was found between the version 2.3-predicted and measured rutting of total asphalt concrete layer and subgrade for thick and thin pavements.

scholarly journals New South African records of Erysiphaceae from the Transvaal II

1985 ◽  
Vol 51 (5) ◽  
pp. 339-343 ◽  
Author(s):  
G.J.Ivla. Gorter ◽  
A. Eicker
Keyword(s):  
South African ◽  
New South

Stellarioides littoralis (Asparagaceae, Scilloideae), a distinct new species from eastern South Africa

Phytotaxa ◽  
2014 ◽  
Vol 177 (5) ◽  
pp. 261 ◽  
Author(s):  
Neil R. Crouch ◽  
Mario Martínez-Azorín ◽  
Angela J. Beaumont ◽  
David Styles
Keyword(s):  
South Africa ◽  
New Species ◽  
South African ◽  
Endemic Species ◽  
New South ◽  
Morphological Features

A new South African endemic species, Stellarioides littoralis is described and illustrated, with data provided on morphology, ecology and distribution. The species appears to be closely related to S. longibracteata and whilst it shares in common an epigeal habit of the bulb with the latter species, several reproductive and vegetative morphological features clearly distinguish it. The affinities and divergences with other close allies are also discussed.

New South African Review 3: The second phase – tragedy or farce? (John Daniel, Prishani Naidoo, Devan Pillay and Roger Southall, eds)

2020 ◽  
Vol 36 (1) ◽  
Author(s):  
Dirk Kotzé
Keyword(s):  
South Africa ◽  
South African ◽  
Social Practice ◽  
New South ◽  
Second Phase ◽  
Human Sciences ◽  
The South ◽  
Negotiated Settlement ◽  
The Third ◽  
Direct Competition

As the title indicates this publication is the third issue in a series of reviews. The first issue was subtitled 2010: Development or decline? (2010) and the second was New paths, old promises? (2011). These publications are edited in the Department of Sociology at Wits University as part of its Strategic Planning and Allocation of Resources Committee (SPARC) Programme. The series is intended to be a revival of the South African Review edited by the South African Research Service and published by Ravan Press in the 1980s and early 1990s. Arguably one of the best known of these series was issue seven edited by Steven Friedman and Doreen Atkinson, The Small Miracle: South Africa's negotiated settlement (1994). The latest publication should also be seen as direct competition for the Human Sciences Research Council's (HSRC) regular publication, State of the Nation. The New South African Review 3 is organised into four parts, namely Party, Power and Class; Ecology, Economy and Labour; Public Policy and Social Practice; and South Africa at Large. The four editors introduce each of the sections, consisting of 16 chapters in total. Thebook's format appears to be that of a yearbook but it is not linked to a specific year. It is therefore not in the same category as for example the South African Institute of Race Relations' annual South Africa Survey. The Review is organised around a theme, albeit very general in its formulation, and in the case of the third issue it is also not applicable to all its chapters. At the same time, though, it is not a yearbook as the choice of chapters and their foci are on the latest developments. 

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