Improving traffic load outcomes for impact assessment of existing pipes under new infrastructure

Infrastructure upgrades often encounter buried pipes that are impacted by traffic loading. Depending on the outcome of impact assessment, pipe diversion or protection works are often required. Given the significant constraints in working space, working hours and traffic management, pipe diversion or protection works often result in significant impacts on project schedule and cost.

An integral part of impact assessment is the evaluation of vertical stress transferred to pipe level from traffic loads. Australian Standards such as AS 5100.2(2017) and AS/NZ 3725(2007) provide guidelines on stress distributions under traffic load, treating the ground as a “uniform elastic soil mass”. Given the economic implications, the authors consider that a multi-layered approach offers benefits compared to this approach by accounting for greater vertical stress dissipation resulting from overlying stiffer pavement layers.

Multi-layered stress analyses are routinely carried out by pavement engineers to evaluate stresses within pavement layers and the pavement subgrade. However, layered modelling techniques are often not applied in impact assessment of pipes buried under pavements. This paper presents multi-layered stress analysis for a number of load cases including both road and light rail loadings. Typical pavement configurations have been considered and a series of plots have been developed giving vertical stress distributions under these conditions. These vertical stress distributions are compared with those resulting from the AS 5100.2(2017) and AS/NZ 3725(2007) approaches to demonstrate the potential benefits of adopting multi-layered stress distributions.