Mwanga, Mgeni Jumbe2020-04-232020-04-232016Mwanga, M. J. (2016) Effects of wide base tyres on flexible pavement structures in Tanzania: a case study of Ilula – Iringa road section, Master dissertation, University of Dar es Salaam, Dar es Salaam.http://41.86.178.5:8080/xmlui/handle/123456789/10013Available in print form, East Africana Collection, Dr. Wilbert Chagula Library, Class mark ( THS EAF TE250.T34M852)Although wide-base tyres offer potential benefits to the trucking industry, these tyres have been associated with a potential increase in pavement damage compared to dual tyre assemblies. Because trucking agencies should not gain economic advantage at the cost of increased road repairs, the benefits of wide-base tyres to the trucking industry should be balanced with the potential increased costs to pavement agencies. To achieve this balance, it is necessary to accurately quantify the damage induced by wide-base tyres and dual tyre assemblies. This study dealt with investigation on the characteristics of freight vehicles in Tanzania in relation to wide base tyre applications, evaluation of pavement damage caused by wide base tyres and recommending axle weights for axles fitted with wide base tyres. Multi-Layer Elastic Theory (MLET) was the tool for analysis. South African Mechanistic Empirical Design software (mePADS) was used to predict pavement responses. Using South African Mechanistic Design Method (SAMDM) transfer functions, five failure modes under each axle load were calculated. Tyre sizes 365/70R22.5, 385/65R22.5, 445/50R22.5,455/55R22.5, 495/45R22.5 and the conventional dual-tyre11R22.5 were investigated. The results of the field study indicate that the component of freight vehicles fitted with super single tyres along TANZAM highway, where a case study area is located is 31.3%. Analysis of results showed that old generation of wide base tyres are more damaging than the New Generation of Wide Base (NGWB) Tyres. NGWB has less effect on fatigue failure of Hot Mix Asphalt (HMA) layer. However, it was found to cause more damage on rutting to granular layers and effective fatigue of cemented layers. The extent of damage was found to decrease with increase in tyre width. The wide base tyres can provide equivalent damage if their axle loads are reduced to certain limits as recommended in this study. The recommended axle loads for single axles are 8.4, 8.75, 9.25 and 9.75 tones for 385, 445, 455 and 495 mm tyre sizes respectively. Recommended axle masses for tandem axles are 13.5, 14.5, 16 and 16.4 tones respectively. A universal 21.5 tones for tridem axles under all wide base tyre sizes was recommended.enPavementsLive loadsPavementsFlexibleIlula -Iringa roadTanzaniaThesis