Failure characteristics of concrete pipes with pre-existing cracks

Urban ground subsidence accidents have become frequent in recent years, mainly due to cracked concrete sewer pipes. Based on the discrete element method (DEM), the process from crack-initiation to the formation of penetrating macrocracks were investigated and crack-initiation load and failure load were calculated. The results showed that numerical results were in good agreement with the experimental results, thus verifying the effectiveness of the DEM calculation results. The crack-initiation load and failure load of concrete pipes varied when different parameters were involved. The diameter of pipe had the greatest impact on the crack-initiation load and failure load, followed by the crack position. The crack dip angle did not show any significant influence on the failure load. The crack depth significantly affected the deformation characteristics prior to crack initiation. The diameter of pipe and crack depth had a minor impact on the failure mode of concrete pipes. However, the crack dip angle determined the path of crack propagation while the crack position determined the crack initiation location and failure mode of the concrete pipes.