Numerical simulation to the effect of applying rationing system on the stability of the Earth canal: Birmana canal in Iraq as a case study

Abstract Extreme conditions will cause the water level of high fill canal segment to change suddenly, which will affect the velocity and pore pressure of the slope. A 9 km irrigation earth canal in the city of Alsyahy, 15 km away from Al-Hilla city, and branching off from the left side of Shatt Al-Hilla at 57 km, was studied. The aim of this work is to study and analyze the effect of rationing system on the Birmana earthen canal during rapid drawdown case. Finite element modeling with Geo-Studio software was used in the present study to analyze the combined seepage and slope stability for three cycles. The resulting minimum safety factor obtained from the analysis using the saturated and unsaturated soil model was found to be 1.161, 1.142, 1.159, and 1.2 from the Janbu, Bishop, Morgenstern-Price, and Spencer methods, respectively. The factor of safety (FOS) values in three cycles are less than the required value. Finally, the FOC decreased by 66% from its value before the rationing system was applied, the area of canal and slip surface increased by 77 and 14%, respectively, due to the applied rationing system. These changes led to an irregular water distribution along the canal, in addition to a reduction in road width.