oedométeres

An oedometer is a laboratory device used to measure the one-dimensional compressibility and consolidation characteristics of a soil sample. The term "oedometer" derives from the Greek word "oidein," meaning to swell, and "metron," meaning measure. The apparatus typically consists of a cylindrical steel ring, known as a consolidometer ring, into which the soil specimen is placed. The ring is designed to prevent lateral expansion of the soil, thus enforcing one-dimensional strain conditions. A porous stone is placed on top of the soil specimen to allow for the free passage of water while preventing soil particles from escaping. A load is applied to the porous stone, typically in increments, through a lever arm system or a dead weight. As the load is applied, water is squeezed out of the soil pores, causing the soil specimen to decrease in height. The change in height, which represents the vertical deformation, is measured over time using a dial gauge or a displacement transducer. The applied load is usually increased in a stepwise manner, and readings are taken at specific time intervals. The data collected from an oedometer test allows for the determination of important soil parameters such as the coefficient of consolidation ($c_v$), the coefficient of volume compressibility ($m_v$), and the preconsolidation pressure ($p_c$). These parameters are crucial for predicting the settlement of structures built on soil foundations and for assessing the soil's behavior under load.