The critical design aspect ensuring the long-term stability of a levee's foundation against uplift pressures caused by subsurface water flow is the seepage cutoff, often complemented by filter layers and drainage systems. Subsurface water flow, also known as seepage, occurs when water from the impoundment side of the levee moves through the permeable foundation soils beneath the levee, driven by a difference in water levels, known as the hydraulic head. As this water flows, it exerts an upward force called uplift pressure, which is essentially the pore water pressure acting on the base of the levee foundation, primarily on the downstream side. Excessive uplift pressure can reduce the effective stress in the soil, leading to a loss of shear strength and potentially causing hydraulic heave or even a 'boil' where soil particles are carried away, leading to foundation instability and fa....
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