What is the effect of ground water on lateral soil pressure?

Groundwater plays a significant role in the calculation of lateral soil pressure, particularly when dealing with submerged conditions. In the context of soil mechanics and the behavior of earth pressures on retaining structures, the concept of submerged unit weight becomes crucial.

When a soil mass is saturated with groundwater, the effective stress within the soil is altered due to the buoyant force acting on the soil particles. The submerged unit weight of the soil is defined as the total unit weight of the soil minus the unit weight of water. This means that when groundwater is present, the lateral earth pressure should be calculated using this submerged unit weight, as it better represents the actual stress conditions acting on retaining structures or during excavation.

Using submerged unit weight allows engineers to accurately determine parameters such as active earth pressure (Ka) or passive earth pressure (Kp) in saturated conditions, which would be essential for the stability analysis of structures against lateral loads. Therefore, the appropriate practice in geotechnical analysis when considering groundwater is indeed to work with the submerged unit weight to reflect the influence of groundwater on lateral soil pressure accurately.