Abstract
Cemented and uncemented aggregate materials form the main component of road pavements, and play a key role in pavement behaviour under vehicle-induced cyclic loads. In this paper, the Discrete Element Method (DEM) was used to simulate the response of these aggregate materials under various loading conditions. Initially, aggregates of five different shapes and four different sizes, assembled at a certain volume ratio, were subjected to compression tests under constant confining pressure. The results indicated that: (i) cracks initiate more easily in larger particles and in the angular rocks at sharper corners; (ii) shear cracks occur more frequently than tensile cracks; and (iii) more micro fractures are obtained with increasing the confining pressure. Additionally, four different cyclic loadings were applied to a simulated flexible pavement with a Cement Treated Base (CTB) layer to understand the impact of loading type on pavement behaviour. The results showed that: (i) settlement of the CTB layer increases significantly with increasing the stress amplitude and decreased with increasing vertical loading frequency for sinusoidal vertical loading; and (ii) more settlement occurs in the CTB layer under cyclic moving wheels carrying constant vertical loads than that caused by cyclic moving wheels carrying sinusoidal vertical loads both at the same mean stress.
1. INTRODUCTION
The breakage of particles relies on multiple factors; namely, particle size distribution (PSD) [1], particle shape [2, 3], confining pressure [4, 5], and loading conditions [6]. Laboratory observations show that the fracturing of different types of particles depends heavily on their contact with neighbouring particles [7]. This has been visualised by numerical simulations of circular particle assemblies under compression [8] and inter-particle breakage of irregular aggregate assemblies having limited and arbitrary particle sizes [9, 10]. However, to better understand particle breakage caused by particle interactions, further study on various irregular particles having specified sizes and volume ratios should be performed.
