Mechanistic design of concrete block pavements

Md Mizanur Rahman, Simon Beecham, Elizabeth McIntyre and Asif Iqbal

Concrete block pavements consist of a layer of rigid, specially shaped and jointed paving blocks that are overlaid on a bedding course layer. The joints of these pavers create an ‘interlocking’ action, which makes the pavement stiffer and stronger with progressive loading. Therefore the design concepts for flexible pavements cannot be directly adapted for concrete block pavements. Instead a mechanistic design method is required, which is too complex to be undertaken by hand calculation and requires the use of computer analysis. This paper describes the development of a new software program (DesignPave), which has been developed in conjunction with the Concrete Masonry Association of Australia. The program’s methodology and design procedure involve: a) estimation of the number of design traffic vehicles (NDT) and traffic loading spectra; b) modelling of progressive interlocking and stiffness development of the block layer; c) stress-strain analysis of a multi-layer pavement system; and d) application of rutting and fatigue criteria suitable for block pavements. This paper uses DesignPave to produce design curves that describe the relation between design thicknesses with NDT. The design curves for different layer systems are compared to identify appropriate subgrade CBR and NDT for a layer system. The different layer systems include a granular base course, a granular base course with a sub-base course and a granular base course with a stabilised sub-base course. The DesignPave program also produces extensive technical documentation for use in common engineering practice.