What is a piezometer primarily used for in geotechnical engineering?

A piezometer is primarily used for measuring pore water pressure, which is a critical factor in geotechnical engineering. Pore water pressure refers to the pressure exerted by water within the soil's voids and plays a significant role in the stability and behavior of soil masses. By monitoring pore water pressure, engineers can assess the effective stress within soil, which is vital for understanding soil strength, stability of slopes, and the behavior of foundations. Accurate measurement of pore water pressure helps in making informed decisions regarding the design and analysis of geotechnical structures and managing issues such as soil liquefaction, settlement, and lateral earth pressures.

In contrast, measuring soil moisture content, evaluating soil density, and assessing soil permeability involve different tools and methods that focus on different aspects of soil behavior. While these topics are fundamental in geotechnical engineering, they do not directly relate to the specific function of a piezometer. Thus, its specialized role in measuring pore water pressure sets it apart as an essential instrument in the field.