Abstract

The talk presents the methodologies and results of experimental studies aimed at measuring soil pressure at a structural boundary as it interacts with the surrounding soil under load, and soil pressure which develops within a particulate/soil medium.

The studies have been carried out using a newly designed and constructed soil pressure cell which is based on the null concept. The measurement system is based on active sensing technology. The response of the device is unaffected by the parameters which plague traditional soil pressure cells. Response is unaffected by soil stiffness, stress history, particle size and soil type. In fact calibration of the system is not required.

An in-soil version of the null soil pressure measurement system has been used in the measurement of lateral earth pressures of granular soils for at rest earth conditions. Four uniformly graded soils were tested; from a fine dune sand of particle diameter 0.15mm, through a crushed stone gravel, of particle size, 12-15mm.

Two significant observations are made and discussed based upon the data presented.

• For initial loading, the coefficient of lateral earth pressure, Ko, was found to be higher for soil placed in dense conditions in comparison to that measured for the same soil placed in loose conditions. This observation was seen in the case of all soils tested.

• The development of horizontal pressure during unloading and reloading was found to be very similar to that of initial loading. Relatively little hysteresis was noted with only limited variation between different soils.