A series of rigid-body and articulated commercial vehicles were used to investigate the influence of axle load, axle spacing and vehicle speed on the strains developed in an experimental pipeline under impact and abnormal wheel load conditions. The 100mm diameter cast-iron pipeline was buried, in both good and poor bedding conditions, at a depth of cover of 0.7m beneath a weak pavement. Vehicle impact loadings induced by a 40mm high plank used to stimulate a surface irregularity caused an increase in pipe strain as the vehicle speed was increased. The maximum bending strains were associated with maximum axle loads although, in general, lighter axles induced larger impact factors. Under the most severe condition of an abnormal axle load of 13.4mg impacting at speed, maximum strains of 260 x 10 to the minus 6 and 125 x 10 to the minus 6 were measured in the poorly and well bedded pipes respectively. After trafficking by 1200 axles, the residual strains in the poorly bedded pipes increased to 300 x 10 to the minus 6 recorded during pipeline installation. The residual strains in the well bedded pipes were hardly affected by trafficking. (Author/publisher)
Abstract