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

New calibration of Neogene radiolarian events in the North Pacific

New age models for twelve Deep Sea Drilling Project sites in the North Pacific have been produced, based on (in order of importance in our dataset) a recompilation of previously published diatom, calcareous nannofossil and foraminifer first and last occurrences, and magnetostratigraphy. The projected ages of radiolarian first and last occurrences derived from the line of correlation of the age/depth plots have been computed from these sites, and 28 radiolarian events have thereby been newly cross calibrated to North Pacific diatom and other stratigraphy. Several of the North Pacific radiolarian events are older than in previously published equatorial Pacific calibrations, and some may be diachronous within the North Pacific. These patterns may be due to complex latitudinal patterns of clinal variation in morphotypes within lineages, or to migration events from the North Pacific towards the Equator