A modified Mohr-Coulomb model to simulate the response of buried pipes subjected to large ground displacement

At the present time, it is very common in practice (industry as well as in research) to utilize Mohr-Coulomb to simulate the soil behaviour in the application of soil-structure interaction problems. The model is often chosen considering its simplicity, ease of use, reasonable computational time and the high level of understanding among the engineers. However, the linear elastic-perfectly plastic Mohr-Coulomb model is unable to predict the softening behaviour of material and hence to predict the pipe load accurately when subjected to large soil movements such as from landslides or earthquakes. A user defined modified Mohr-Coulomb model is developed to capture the strain softening behaviourof soil and to simulate the pipeline response subjected to large ground deformation. The softening behaviour of the model has been calibrated on the basis of direct shear test data, and triaxial test data have been used for calibrating the yielding and flow characteristics of the model. The calibrated model has been applied to simulate the response of HDPE pipeline undergoing different ground displacements. Finally, the model response was used to develop a strain demand model for buried pipelines facilitating the risk assessments.