Effect of Bedding Thickness on Behavior of Rigid Pipes as Determined by Using Numerical Crack Modeling

Numerical analyses are performed to find the loading capacity of buried reinforced concrete pipes at different performance levels. Different geometrical and material parameters play an important role in the total behavior of the pipe system. The effects of bedding thickness, middle-bedding compaction level, steel cages, and pipe thickness are studied by using dynamic nonlinear analysis capable of modeling the complex cracking behavior of the concrete pipes. Contact elements are used for modeling the actual contact behavior between the pipe's surface and its surrounding soil. The Drucker–Prager plasticity model and the isotropic hardening plasticity model were used for soil and steel materials, respectively. Two structural performance levels are defined for pipes, the first one being the instance in which the crack initiates in the pipe's surface. The second-higher performance level is defined as the time in which the crack opens. The results of the study show that increasing the bedding thickness has a significant effect on the loading capacity of the system. This increase in capacity is more dominant for smaller-diameter pipes. Providing middle beddings with lower levels of compaction can also be effective in increasing the loading capacity of the pipes.