A SOIL STRESS TRANSDUCER FOR MEASURING IN-SITU SOIL STRESSES

A soil stress transducer has been designed to measure normal stresses in six different directions, and therefore enable the total state of stress in a soil to be defined. The transducer is relatively small with its active faces on an approximate sphere of diameter 40 mm, and is simple to manufacture, robust, and reliable in use. Calibration procedures have been developed which show that the transducer will register applied stresses reliably. The transducer is installed in a horizontal hole bored from a pit using a technique which ensures that it is in full contact with the soil. Field testing has shown that in conjunction with a moderately fast data acquisition system it is capable of measuring detailed stress histories under the tyres of moving vehicles.