Instruments for determining stress displacements in soils

The basic theory, design, and construction of a 10-inch diameter soil pressure cell are discussed. Finite element analytical techniques were used in assessing various cell geometric shapes that would minimize registration error regardless of cell orientation to the major principal stress. Approximately 170 cells of an optimum geometric shape were used in the evaluation of soil stresses around a buried culvert and its composite embankment. Their output data are considered and the device is compared to three types of other commercially available soil and interface pressure cells installed in conjunction with this model. Calibration procedures are also discussed. The design and construction of a continuous settlement profile gage composed of a transducer sensing head and a horizontally placed 2-inch diameter plastic pipe are also examined. The transducer is pulled through the pipe by means of cable raceway. Water within the pipe provides the static reference head for all settlement measurements. Accuracy is plus or minus 0.05 ft of settlement. Field performance of the device is included.