Measuring Gypsum Rock Strength While Coring with a Laboratory Rock Core Driller-Paper

Paper

Pdf Summary

The study evaluates whether Measurement-While-Drilling (MWD) data can estimate the unconfined compressive strength (UCS) of gypsum rock. The researchers instrumented a laboratory core drill to record axial force (down pressure), torque, rotational speed, and penetration rate. A removable aluminum coupler fitted with strain gauges measured force and torque; a string potentiometer and Hall Effect sensor measured penetration and rotation.<br /><br />Gypsum blocks from an abandoned Michigan mine were secured for coring. Drilling conditions were varied to identify settings that minimized drilling energy; optimum down pressure generally ranged from 73 to 175 N. The resulting cores were prepared and tested for UCS under dry and saturated conditions, following ASTM D7012. Dry UCS values ranged from 10 to 59 MPa, while saturated values ranged from 5 to 38 MPa.<br /><br />The team calculated two compound MWD measures—specific energy and drillability—and compared them with UCS. Both measures correlated with strength in dry and saturated samples. Specific energy performed better, with coefficients of determination (R²) of 0.9664 for dry samples and 0.9154 for saturated samples. Drillability produced R² values of 0.9052 and 0.8383, respectively.<br /><br />The results suggest that laboratory-scale MWD measurements can provide useful estimates of gypsum strength despite variability caused by impurities and fractures. The approach could support geotechnical characterization and assessment of underground mine stability, although its correlations should be further validated for other rocks and drilling systems.

Keywords

Measurement-While-Drilling

MWD data

gypsum rock

unconfined compressive strength

UCS estimation

specific energy

drillability

laboratory core drilling

gypsum mine

geotechnical characterization