What is the effect on pore water pressure when the water table rises?

When the water table rises, pore water pressure increases. This phenomenon occurs because pore water pressure is the pressure exerted by water within the soil's voids or pores. As the water table rises, more water saturates the soil, leading to an increase in the hydraulic head in the pores, which contributes directly to pore water pressure.

In a saturated soil condition, the total stress in the soil mass remains constant, but as the amount of water increases due to the rise in the water table, the pore water pressure increases proportionately. This is critical in geotechnical engineering, as increased pore water pressure can affect the soil's effective stress, shear strength, and overall stability.

Understanding pore water pressure is essential for assessing the behavior of soil, particularly in conditions such as slope stability, foundation design, and during construction activities where groundwater management is crucial. The relationship between the water table and pore water pressure is a key concept in soil mechanics and civil engineering practices.