Numerical modelling of buried steel pipeline overlaying expansive soil

Pipelines rested on expansive soils are subjected to uplift forces due to soil swelling that caused deformations and bending. Numerical modeling was carried out by using PLAXIS 3D-2013 software, in which modeling the soil by using Hardening Soil Model. The various spacing between helical piles is used to reduce the vertical movement of pipeline rested on expansive soil. This study showed that the reduction in uplift movement of pipeline founded on expansive layer, when L/D (116, 146, 176) is (39, 77, 99) % for spacing of 6.67dh and (28, 62, 90) % for spacing 10dh and (12, 43, 77) % for spacing 13.33dh. Uplift movement of pipeline founded on expansive layer decreases to zero values when L/H ratio should be (2, 3.4, and 3.7) in the stable zone for spacing's 6.67dh, 10dh and 13.33dh respectively. In general, the presence of helical piles below pipeline resisted and controlled the vertical movement of expansive soil and regarded good solution to mitigate this problem.