Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The southbound screener lane of the Heidelberg Traffic Control Centre received structural
improvements by means of an ultra thin continuously reinforced concrete pavement
(UTCRCP) overlay. This experimental overlay forms part of the South African National
Roads Agency Limited’s innovative highway repair strategy on existing pavements that have
exceeded design life. The primary objective of this study was to characterize the UTCRCP
overlay with regard to crack spacing formation under accelerated pavement testing (APT).
Characterization comprised of empirical modelling techniques, statistical analysis, non
destructive testing and software simulations. Pavement deflection responses were
empirically and linear elastically converted to input parameters. These parameters were
used in the mean crack spacing prediction model of the Mechanistic-Empirical Pavement
Design Guide (M-E PDG). Observed cracking under APT was recorded and analyzed by
means of descriptive statistics. The outcome of the M-E PDG’s mean crack spacing and the
statistics of the observed cracking were evaluated against cncPave simulations.
Initial shrinkage crack formations ranged from 500 mm to 900 mm, with a mean spacing of
695 mm. Subsequent secondary cracking reduced the segments, delineated by initial
cracking, to intervals consisting of 100 mm to 350 mm. A statistical analysis of the observed
cracking indicated that traffic had little effect on the transverse crack spacing formation. The
observed cracks yielded a mean spacing of 296 mm, compared to the 186 mm of the M-E
PDG mean crack spacing calculation. cncPave simulations indicated that the expected
range of cracking would fall between 237 mm and 350 mm with a probability of 50% that
crack spacing would exceed 265 mm. The 50th percentile of the observed cracks resulted in
a spacing of 233 mm. The APT project was limited to a single test section. No pavement
failures occurred during the APT project. A total of 2.8 million 80 kN load repetitions were
applied to the UTCRCP. However circular crack formations regarded as a punchout
development have formed on the UTCRCP test section.
Circular cracks formed around weaknesses in the pavement system. The prediction of these
punchout formations incorporates the mean crack spacing result. Occurrence of mean crack
spacing forms part of a crack spacing distribution defined by a range. Therefore designing a
punchout prediction model for UTCRCP should include the characteristics and range of the
crack pattern and not merely the mean crack spacing value.
Key Words: UTCRCP, APT, Mean Crack Spacing, Punchout, Descriptive Statistics,
cncPave, M-E PDG, Transverse Cracks, Dense Liquid Foundation, Elastic Solid Foundation. / AFRIKAANSE OPSOMMING: Die suidwaartse moniteerings laan van die Heidelberg Verkeersbeheer Sentrum, het
strukturele verbetering ondergaan deur die konstruksie van ‘n ultradun aaneen-gewapende
betonplaveisel (UDAGBP) wat dien as ‘n deklaag. Hierdie eksperimentele deklaag is deel
van die Suid-Afrikaanse Nasionale Paaie Aggentskap Beperk (SANRAL) se vernuftige
deurpadherstelstrategie vir bestaande deurpaaie waarvan die ontwerplewe verstryk het. Die
primêre doel van hierdie studie is om die UDAGBP te karakteriseer, met betrekking tot
kraakspasiëring, deur middel van Versnelde Plaveisel Toetsing (VPT).
Die karakteriseringsproses het bestaan uit empiriese moduleringstegnieke, statistiese
ontleding, nie-destruktiewe toetsmetodologieë en sagtewaresimulasies. Die plaveiseldefleksiegedrag
is empiries en linieêr elasties ontleed en omgeskakel na invoerparameters.
Hierdie parameters is gebruik in die peilingsmodel vir gemiddelde kraakspasiëring van die
Meganisties-Empiries Plaveisel Ontwerpsgids (M-E POG). Waargenome kraakspasiëring na
die afloop van VPT is opgeteken en deur middel van beskrywende statistiek ontleed. Die
resultate van die M-E POG se gemiddelde kraakspasiëring en die statistiese ontleding van
die waargenome krake is geëvalueer teenoor cncPave simulasies.
Aanvanklike krimpingskrake het gevorm met wisselende kraakspasiëring tussen 500 mm en
900 mm met ‘n gemiddelde spasiëring van 695 mm. Daaropvolgende krake het die
aanvanklike segmente, wat gevorm het tydens die aanvanklike krimpingskrake, verkort na
intervalle van 100 mm tot 350 mm. ‘n Statistiese ontleding van die waargeneemde krake het
aangedui dat verkeer weinig ‘n aandeel het in die dwarskraak-vormingsproses. Die
waargenome krake het ‘n gemiddelde spasiëring van 296 mm in vergelyking met 186 mm
van die M-E POG se gemiddelde kraakspasiëring berekening. cncPave simulasies het
aangedui dat die verwagte kraakspasiëringsgrense tussen 237 mm en 350 mm is en ‘n 50%
waarskynlikheid dat die kraakspasiëring meer as 265 mm is. Die VPT projek is beperk tot ‘n
enkele toetsseksie. Geen plaveiselfalings is waargeneem gedurende die VPT projek nie. In
totaal was 2.8 miljoen as-lasherhalings aangewend op die UDAGBP. Daar het egeter
sirkelvormige kraakformasies, wat beskou word as ponsswigting, ontwikkel op die UDAGBP
toetsseksie.
Sirkelvormige kraakpatrone het gevorm rondom swak plekke in die plaveisel. Die
peilingsmodelle van hierdie ponsswigting maak gebruik van die gimiddelde
kraakspasiëringsresultaat. Die verskynsel van gemiddelde kraakspasiëring in hierdie studie
is deel van ‘n kraakspasiëringsverdeling, gedefinieerd deur ‘n spasiëringsgrens. Daarom
moet die kraakspasiëringskarakteristieke en spasiëringsgrense in ag geneem word in die ontwerpsproses van ‘n UDAGBP ponsswigting-peilings-model, nie slegs die waarde van die
gemiddelde kraakspasiëring nie.
Sleutel woorde: UDAGBP, VPT, Gemiddelde Kraakspasiëring, Ponsswigting, Beskrywende
Statistiek, cncPave, M-E POG, Transversale Krake, Digte Vloeistof Fondasie, Elasties-
Soliede Fondasie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/6772 |
| Date | 03 1900 |
| Creators | Gerber, Johan Andries Kritzinger |
| Contributors | Jenkins, K. J., University of Stellenbosch. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA, English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 116 p. : ill. |
| Rights | University of Stellenbosch |
Page generated in 0.0023 seconds