Thesis (M.Ing.)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Laterites are used extensively in the tropics as road building materials in unbound
base, sub-base layers and in surface layers. However, most base course specifications
usually require the provision of crushed and graded stone or stabilized base and often
exclude the general use of as-dug laterites or other naturally occurring gravels.
Various field studies in the past have clearly indicated that many lateritic gravel
deposits can be used successfully as base course materials in roads carrying low to
medium traffic without incurring additional maintenance costs and with considerable
cost savings in pavement construction rehabilitation.
Further research is needed for the more precise definition of the relationship between
laterite characteristics, traffic loading, environment, and pavement performance. In
this study, extensive use was made of static and cyclic triaxial testing to investigate
the fundamental behaviour of a lateritic gravel material. The tests produce information
for characterizing the shear strength, stress-strain properties and behaviour under
repeated loading. The gravel was sourced from stockpile at Malans Transport borrow
pit at Maaitjies Kuil near Cape Town. Testing was conducted on the material both as
granular material and stabilized with cement and foamed bitumen. Testing was done
under various conditions of stress, moisture and compaction. The resilient modulus of
the lateritic gravel was found to be affected by moisture and compaction apart from
the stress condition. Well known models were used to characterize the stressdependent
resilient modulus. A model for prediction of permanent deformation was
developed which together with the resilient modulus model were applied to the design
of a light pavement structure composed of lateritic gravel base. / AFRIKAANSE OPSOMMING: Lateriete word wydverspreid gebruik in die trope as 'n padbou materiaal. Die
materiaal word gebruik in ongebonde kroonlae, stutlae en oppervlaklae. Die meeste
spesifikasies vir kroonlae vereis dat gegradeerde gebreekte klip of gestabiliseerde
materiaal in die kroonlaag gebruik word. Die spesifikasies maak nie voorsiening vir
lateriet en gruis wat natuurlik voorkom nie. Verskeie veldstudies in die verlede het
duidelik getoon dat lateritiese materiaal met sukses gebruik kan word in die kroonlae
van paaie wat ligte tot medium verkeer dra. Lateriete kan gebruik word sonder
addidionele onkoste vir instandhouding en daar is merkbare kostebesparings wanneer
plaveisels rehabiliteer word.
Die verhouding tussen lateriet eienskappe, verkeerslas, omgewingsinvloede en
plaveisel werkverrigting moet beter gedefinieer word deur verdere navorsing. In
hierdie studie is omvattend gebruik gemaak van eenmalige en herhaalde belasting
drie-assige toetse om die fundamentele gedrag van lateritiese materiaal te definieer.
Hierdie toetse se resultate lewer inligting oor die skuifsterkte, spanning-vervorming
eienskappe en gedrag onder herhaalde belasting.
Die gruis wat gebruik is, is verkry vanaf 'n materiaalopslag by die leengroef van
Malans Transport te Maaitjies Kuil naby Kaapstad. Die materiaal is getoets as
granulêre materiaal en gestabiliseer met sement en skuim-bitumen. Die toetse is
gedoen onder verskillende toestande van spanning, voginhoud en verdigting.
Daar is bevind dat die veerkragtigheidmodulus van die lateritiese gruis nie net deur
die aangewende spanning beïnvloed word nie, maar ook deur die voginhoud en
verdigting van die materiaal. Welbekende modelle is gebruik om die spanningsafhanklike
gedrag van die materiaal te karakteriseer. 'n Model is ook ontwikkel om
die permanente vervorming van die materiaal te voorspel. Die twee modelle vir die
veerkragtigheidsmodulus en permanente vervorming is gebruik om 'n ligte
plaveiselstruktuur mee te ontwerp wat 'n lateritiese kroonlaag bevat.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/51897 |
| Date | 12 1900 |
| Creators | Ng'anjo, Peter |
| Contributors | Van de Ven, M. F. C., Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 1 v. (various pagings) : ill. |
| Rights | Stellenbosch University |
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