Numerical Modelling of Unreinforced and Geosynthetic-Reinforced Sandy Soil Cover over Large-Diameter HDPE and PVC pipes

A realistic estimation of load distribution over the buried structures is necessary for proper analysis of pipes/conduit, culverts and tunnel lining. Pipelines are often constructed in the areas of civil engineering, mining engineering, agriculture and some other areas. For the design of pipeline, it is essential to know the load over it. Load distribution over the buried structures has been investigated scientifically during the past several decades. The method of investigation includes experimental, analytical and numerical methods. The finite-element models based on some commercial software have been developed for load analyses for design of the pipeline and buried structures. The geosynthetic is an effective reinforcement layer to reduce the load over the buried structure. Although some small-scale studies have indicated that the geosynthetic layer can reduce the load over the buried structure, the investigation on a large scale is limited. Therefore, in this paper, an attempt is made to investigate the load-distribution behaviour of geosynthetic layer as a reinforcement within the soil cover over the HDPE and PVC pipes. The study has been carried out by developing a numerical model of the problem using the commercial software PLAXIS 3D. The comparison of HDPE and PVC pips shows that the pressure around the PVC pipe is greater than the pressure around HDPE pipe, while pressure around the larger diameter HDPE pipe is lower than the pressure around the smaller diameter HDPE pipe. The pressure on the crown of the pipe decreases with presence of the geosynthetic reinforcement layer; the optimal distance between geosynthetic reinforcement layer and pipe is equal to the pipe diameter. The pressure reductions on the crown of the HDPE and PVC pipes, having a diameter of 914 mm, are 31% and 27%, respectively. The graphical presentations may be used as the design charts for designing the buried pipes.