DEVELOPMENT OF A SOIL STRESS GAGE FOR THE RANGE 0.05 TO 1 GPA (1 1/2 TO 10 KBAR)

IT IS PROPOSED TO DEVELOP A STRESS GAGE FOR THE RANGE 1/2 TO 10 KILOBARS, SUITABLE FOR USE IN SOIL AND WEAK ROCK, IN FREE-FIELD AND ON-STRUCTURE APPLICATIONS. IN ADDITION TO THE USUAL COMPRESSIVE STRESS SENSING CAPABILITY, THERE WOULD ALSO BE A SHEAR STRESS SENSING OPTION; THE TWO MEASUREMENT CHANNELS COULD ALSO BE COMBINED IN A SINGLE GAGE BODY PACKAGE. FIELD DATA RECORDING COST AND SYSTEM PROBLEMS WOULD BE MINIMIZED BY STAYING WITH THE ELECTRICAL CONFIGURATION OF A CONVENTIONAL LOW-VOLTAGE STRAIN GAGE BRIDGE (PER CHANNEL). THE NATURE OF THE DESIGN INHERENTLY MINIMIZES UNWANTED AMBIGUITIES WITH OTHER STRESS COMPONENTS. THE SMALL SIZE AND FAVORABLE SHAPE OF THE INTERNAL STRUCTURE MINIMIZES AND FACILITATES CORRECTIONS FOR WAVE PROPAGATION EFFECTS WITHIN THE GAGE. A CHALLENGING MINIATURIZED STRAIN GAGING REQUIREMENT IS INVOLVED, AND A SIGNIFICANT PART OF THE PHASE I EFFORT WOULD BE TO DEVELOP THE TECHNIQUE REQUIRED.