STRESS REDUCTION ON BURIED CONCRETE CONDUITS UTILIZING COMPRESSIBLE INCLUSION

Abstract

In recent years, the Kingdom of Saudi Arabia started some huge projects in the field of infrastructure development through all Kingdom regions. Among these projects are the water and sewage systems, which don’t yet cover all of Kingdom cities and regions. With the urban development, the infrastructure projects increased for connecting sewage networks to many areas. At the beginning, cast iron pipes were used in these networks, however they are fragile and need to be treated carefully during installation under the ground. Moreover, by the time, cast iron pipes may cause environmental problems to soil and groundwater due to steel corrosion and rust. Reinforced concrete pipes are considered to be a good and economic choice for sewage pipes since they are less expensive, locally produced, and environmentally safe. The disadvantage of reinforced concrete pipes is that they do not bear large overburden loads of soil to avoid their breakage due to its rigidity. This means they cannot be embedded at large depths underground as it sometimes required in sewage networks. The use of reinforced concrete pipes is not limited to the sewage systems, but they are also used in water and oil transfer as well as in storm water drainage systems and utility tunnels throughout the Kingdom cities. This study investigated how to reduce the stress on rigid conduits under heavy overburden soil loads using EPS-Polystyrene on top of the buried conduits and to identify the disturbance zone above buried pipes to be careful during installation pipes or construct buildings on these zones. This will allow the increase usage of this type of pipes in infrastructure projects throughout the kingdom. iv A full numerical investigation was conducted using finite difference analysis utilizing FLAC (Fast Lagrangian Analysis of Continua). The numerical analysis was verified utilizing an experimental test of a buried pipe in a steel box. A parametric study was done by changing a number of parameters such as pipe diameter, position of geofoam, configuration of the compressible inclusion, modulus of elasticity of soil. The results of the study show the improvement in the usage of reinforced concrete pipes under high overburden pressure by reducing the vertical stress above buried pipes around 95% when using thin layers of EPS-geofoam due to the activation of arch action above the pipe. Pipe diameters and wall thicknesses could be reduced for the same depth by using geofoam. These results will extend the use of this type of pipes in the construction and infrastructure projects throughout the Kingdom.