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Vibratory hammer compaction of granular materials
No full textThesis (MScEng)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Compaction is one of the key processes in the construction of road pavement layers. Not only
is it significant in ensuring the structural integrity of the material in the road layers, but it also
has an influence on the engineering properties and performance of the soil material. A poorly
compacted material is characterised by low density, high porosity and below standard shear
strength. This, as a result causes rutting, moisture susceptibility, potholing, corrugations and
passability problems on the road. Therefore, it is vitally important that field compaction is
done correctly. For this reason, laboratory compaction methods have been developed to
simulate the field compaction process in the laboratory.
The Mod AASHTO test has long been used as the laboratory compaction method of choice
by virtue of its simplicity and the lack of bulky equipment required. However, previous
studies have established that the Modified AASHTO method does not adequately simulate
field compaction criteria especially for cohesionless materials. Two reasons have been
advanced;
The Mod AASHTO compaction method does not adequately simulate the compaction
done in the field when the granular mix is laid;
The compaction method may cause disintegration of the material.
Alternative tests have been considered and much research has focused upon the use of a
modified demolition hammer (vibratory hammer) for laboratory compaction of granular
materials.
This study undertook to evaluate the influence of test factors pertinent to the vibratory
hammer compaction method. The influence of these test factors on compaction time and
obtainable material density was assessed with the objective of developing a compaction
method for granular materials. Vibratory hammer compaction tests were conducted on G3
hornfels, G4 hornfels and G7 sandstone material types and to a lesser extent, reclaimed
asphalt (RA). Densities obtained were referenced to Mod AASHTO compaction density.
Findings of the study showed that, the mass of the tamping foot has a significant influence on
the obtainable compaction density. Other factors such as, moisture content, frequency and
frame rigidity were also found to affect compaction with the vibratory hammer. In addition, it
is shown that the surcharge load does not significantly influence the obtainable compaction density but does contribute to the confinement of the material and restricts the upward bounce
of the hammer.
On the basis of the results and findings, a compaction method was proposed, incorporating
test parameters and factors that would provide ideal results for a set compaction time.
Repeatability tests showed that, the developed vibratory hammer compaction method was
effective in compacting graded crushed stone material types (i.e. G3 and G4) and probably
RA. The test was not as effective on the G7 material. Further studies on this material (G7) are
required.
In addition to the previous testing regime, a comparative assessment of the developed
vibratory hammer compaction method in relation to the vibratory table method was done. The
results show that the vibratory hammer is capable of producing specimens of densities
comparable to those of the vibratory table.
A sieve analysis undertaken before and after compaction showed that compaction with the
developed vibratory hammer compaction method does not result in any significant material
disintegration.
Based on the results of this study, a specification for the determination of maximum dry
density and optimum moisture content of granular material using the vibratory hammer is
recommended.AFRIKAANSE OPSOMMING: Kompaksie is een van die belangrikste prosesse in die konstruksie van die padplaveisel. Dit is
nie net waardevol vir die versekering van strukturele integriteit van die materiaal, maar dit
het ook 'n invloed op die ingenieurseienskappe en vermoë van die grond materiaal. 'n Swak
gekompakteerde materiaal word gekenmerk deur 'n laë digtheid, hoë porositeit, on
onvoldoende skuifweerstand. Die kenmerke maak die material vatbaar vir vogen. Lei tot
spoorvorming, slaggate, golwe en deurgangs probleme op die pad. Dit is dus uiters
noodsaaklik dat veld kompaksie korrek gedoen word. Om hierdie rede, is kompaksie metodes
in die laboratorium ontwikkel om sodaend veldkompaksie te simuleer.
Die “Mod AASHTO” laboratorium kompaksie toets is die gekose laboratorium kompaksie
metode op grond van sy eenvoudigheid en gebruik van minimale toerusting. Vorige studies
het egter bevestig dat die “Mod AASHTO”-metode nie veldkompaksie akkuraat kan simuleer
nie, veral vir kohesielose materiaal. As gevolg van twee hoofredes;
Die Mod AASHTO kompaksiemetode is nie ‘n realistiese en vergelykende simmulering
van kompaksie soos dit in die veld gedoen word nie;
Die kompaksie metode mag verbrokkeling van die materiaal veroorsaak.
Alternatiewe toetse was oorweeg en baie navorsing het gefokus op die gebruik van 'n
aangepaste vibrerende hamer.
Hierdie studie het onderneem om verskeie relevante toetsfaktore van die vibrerende hamer en
hul invloed op die kompaksie en verkrygbare digtheid te bestudeer. Die invloed van hierdie
toetsfaktore op kompaksietyd en verkrygbare materiaal digtheid was geassesseer met die doel
om 'n kompaksiemetode vir granulêre materiaal te ontwikkel.
Vibrerende hammer kompaksietoetse was uitgevoer op G3 hornfels, G4 hornfels en G7
sandsteen materiaal en tot 'n mindere mate herwinde asfalt. Digthede verkry was verwys na
die Mod AASHTO kompaksie digtheid. Resultate van die studie het getoon dat die gewig van
die stamp voet ‘n merkwaardige invloed het op die verkrygbare kompaksie digtheid. Ander
faktore soos voginhoud, frekwensie en raam styfheid het ook getoon om kompaksiedigtheid
te beïnvloed met die vibrerende hammer. Benewens was ook getoon dat die toeslaglading
geen beduidende invloed het op die verkrygbare kompaksie digtheid nie, maar wel bydrae tot
die inperking van die materiaal en verhoed die vertikale terugslag van die hammer. Gebaseer op die resultate en bevindinge was ‘n kompaksiemetode voorgestel wat toets
parameters integreer met toetsfaktore en tot volg ideale resultate vir ‘n gegewe kompaksietyd
voorsien. Herhaalde kalibrasie toetse het getoon dat die ontwikkelde kompaksiemetode
effektief is in die kompaktering van gegradeerde gebreekte klip materiaaltipes (G3 en G4) en
moontlik herwanne asfalt. Die toets was nie so doeltreffend op die G7 materiaal nie. Verdere
studies op hierdie materiaal (G7) is dus nodig.
Addisioneel tot die vorige toets, is bevind dat ‘n vergelykende assesering van die ontwikkelde
vibrerende hammer kompaksiemetode in verhouding tot die vibrerende tafel. Die resultate
wys dat die vibrerende hammer die vermoë het om toetsmonsters met digthede vergelykbaar
met die vibrerende tafel te produseer.
Sifanalise voor en na kompaksie het getoon dat verdigting met die ontwikkelde vibrerende
hamer kompaksie metode nie lei tot die disintegrasie van die materiaal nie. Gebasseer op die
resultate van dié studie was ‘n spesifikasie vir die bepaling van maksimum droé digtheid en
optimale voginhoud van granulêre material aangeraai
Advancing sustainable gravel road construction through innovative nano-emulsion treatment of a micaceous gravel.
No full textDoctoral Degree. University of KwaZulu-Natal, Durban.Materials used for road construction play a critical role in the performance of the pavement structure. Winning and haulage of virgin materials have been highlighted as factors that contribute significantly to the increased construction cost and environmental degradation. In the quest to achieve sustainability, it has been recognised that functionalising locally available materials is one of the ways of tackling the challenge highlighted above. Such materials are enhanced through stabilisation traditionally using products such as cement and lime. However, these (cement and lime) have limitations and various products have been developed and marketed as viable alternatives for material enhancement.
This study evaluated the efficacy of Nano-Modified Emulsion (NME), a relatively new product, for stabilisation of gravel materials, particularly for use as a gravel roadwearing course. NME comprises of Conventional Bitumen Emulsion (CBE) modified with an organofunctional nanosilane. Therefore, the product (NME) draws on the properties of nanotechnology to functionalise and improve properties of materials traditionally considered of marginal quality. Previous studies show that this product has great potential in this regard. However, it is recognised that current knowledge of the product is limited and further research is required on the fundamental properties and behavioural traits of NME stabilised materials (NMESMs) to streamline concepts, understanding, leading to the development of design guidelines of the materials. A marginal quality micaceous gravel material was chosen as a suitable candidate to demonstrate the efficacy of the NME. The material, stabilised with varying NME applications from 0.7% to 1.5%, was evaluated for various engineering properties, including mechanical strength, stiffness and deformation characteristics. Results of tests for mechanical strengths conducted through California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS), Indirect Tensile Strength (ITS) and Static Triaxial Tests (STT) showed improved material properties by more than 70%. It was observed that minimal applications of NME are required to achieve specified strengths and that increasing the application dosage does not significantly improve material strength. The NME is also shown to impart hydrophobic properties on the gravel material such that increased applications of NME increase the gravel’s resistance to moisture damage as determined by the Moisture-Induced Damage Ratio (MDR). The STT results demonstrate that the NME improves the shear strength of materials by increasing the cohesion parameter by up to 54% while the angle of friction remains virtually unchanged. The resilient modulus of NMESMs exhibits a combination of stress-dependent and -independent behaviour and it was determined that the parabolic model suitably represents this behaviour. Results of plastic strain tests also show that NMESMs provide better performance with regard to resisting deformation. Modelling and pavement structure analysis was implemented using a Finite Element (FE) based software, ANSYS 2022 R2. This was done to simulate the performance of the material in an actual pavement structure. It was determined that incorporating a NMESM layer as a wearing course on a gravel road pavement structure improves pavement responses to loading i.e. strain and deflection by up to 14% and 28%, respectively. The use of NMESM also reduces the thickness of the layer, resulting in a saving on materials. Additional studies are recommended for Life-Cycle Cost Analysis (LCCA) to help in quantifying cost-benefit ratios of implementing NMEs in industry
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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