How does increased pore water pressure affect soil behavior during loading?

In geotechnical engineering, effective stress plays a critical role in understanding soil behavior under loading conditions. The effective stress principle, formulated by Karl Terzaghi, states that the effective stress in a soil mass is the difference between the total stress and the pore water pressure.

When pore water pressure increases, typically due to saturation or loading, the total stress acting on the soil remains constant, but the pore pressure component of the stress increases. As a result, the effective stress decreases because a higher pore water pressure counteracts part of the total stress. Since effective stress is a key factor in determining soil strength, a decrease in effective stress leads to a reduction in soil strength. This phenomenon can make the soil more susceptible to failure, particularly in saturated conditions, highlighting the importance of managing pore water pressure in soil engineering practices.

Hence, the situation described reflects how increased pore water pressure reduces both effective stress and soil strength, confirming the correctness of the statement that increased pore water pressure negatively impacts soil behavior during loading.