Soil-Embedded and Oil-Immersed Soil Stress Gage Calibration Tests
Abstract
Soil stress measurements are used to determine or deduce many aspects of high-explosive (HE) tests; hence, accurate calibrations of soil stress gages are essential to proper interpretation of test events. The soil stress gages typically used in HE tests are currently calibrated hydrostatically. The result of a hydrostatic is linear for both loading and unloading. But soils do not typically behave as linear elastic materials, i.e., soil stress-strain behavior calibration is usually both nonlinear and hydrostatic. A calibration technique is needed to convert the voltage output of a soil stress gage to a pressure based upon the soil backfill material in which the gage is embedded. Calibration tests were conducted on low-range (to 30 MPa) and high-range (to 70 MPa) diaphragm-type soil stress gages, denoted LRSE and HRSE, respectively, immersed in oil and embedded in soil. Three soil types were used: (1) flume sand, SP, (2) Yuma clayey sand, SC, and (3) Vicksburg loess (silty clay), CL. Calibration tests were conducted in which the voltage output of the gages was recorded. Stress gage calibration tests were also conducted in which the strain output from each of the four individual strain gages in the wheatstone bridge were recorded. The gages were oriented for both vertical and horizontal stress measurements, and calibration tests were conducted on the gages with and without confining rings. The soil-imbedded calibration test results may be used to process raw stress gage data from field tests more accurately than can be achieved using standard oil-immersed calibrations. The results from the strain output tests can be directly compared with the results from finite element gage-simulation calculations.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1997
- Accession Number
- ADA332781
Entities
People
- Jon E. Windham
- Walton C. Dickson