Numerical Investigation of the Effect of Conventional Cut-and-fill Process and Tire-Derived Aggregate Placed on Top of Buried Concrete Pipe on the Pavement Deflection

It is quite common to install buried pipes using the traditional cut-and-fill method. Furthermore, there is a new trend of using compressible materials (e.g., tire-derived aggregate (TDA)) on top of buried pipes to reduce soil pressure applied to buried pipes. However, it is not clear how these processes affect pavement deflection. This paper assesses the effects of the cut-and-fill process and tire-derived aggregate placed on top of a buried concrete pipe on the pavement deflection under the effect of traffic load using validated three-dimensional finite element analysis. Conventional cut-and-fill trench using compacted backfill (CB) and conventional cut-and-fill trench using compacted backfill with a TDA layer on top of the pipe (TDA) have been simulated to address the aim of the work. In addition, highway section (paved road) and unpaved road section have been considered. It has been found that the CB increases the pavement deflections for both paved and unpaved roads. In addition, the TDA increases the pavement deflection for a burial depth range of 1.0 to 2.0 m compared to the CB. However, the difference between the CB and the TDA decreases after the burial depth of 2.0 m. Also, increasing the pipe diameter remarkably increases the pavement deflection for the CB and TDA trench configurations. Increasing the pipe diameter increases the effect of the TDA on the pavement deflection compared to the CB. The results reported in this work provide a useful addition to the literature and could benefit future decision-making regarding the use of the cut-and-fill process or the use of TDA to reduce the soil pressure applied to buried pipes. In addition, experimental investigations are needed to verify the results of this paper due to the lack of experimental studies on the effect of trenching and TDA on the deflection of flexible pavements.