On the earth pressure cell with case histories

Perhaps the most maligned transducer in geotechnics is the earth pressure cell (EPC), a device used to determine average normal stress within a soil mass or at a soil-structure interface. Essentially, the response of an EPC is governed by force equilibrium, and the difficulty with the interpretation of the transduction process involves the actual distribution of normal stress and a possible arching phenomenon, either of which can lead to over-or under-registration when compared to fluid pressure. Furthermore, the transducer itself may complicate the measurement because of a perturbation of the stress field, although this inclusion effect is reduced through proper design of the EPC. The structural response of an EPC is reviewed, and calibration procedures for evaluating nonuniform normal stress and arching are discussed. Two case histories are presented to demonstrate that, with consistent placement procedures and proper calibration, the EPC can provide meaningful data for evaluation of performance.