In-situ Strength Characteristics of Coal Mine Floor Strata in Illinois

摘要

The report presents data on bearing capacity and in-place shear strength characteristics of immediate floor strata. Plate load tests were conducted under as-mined and saturated and/or wet conditions. Borehole shear tests were conducted to determine cohesive strength, angle of internal friction, and failure envelope for floor strata at different depths. An attempt was made to correlate the above data with laboratory determined strength deformation characteristics and engineering index properties of floor strata from ongoing studies. The results indicate the nature of floor strata at the two mines to be very similar. Statistically significant correlations were observed for two sets of variables: (1) ultimate bearing capacity and deformation modulus, (2) natural moisture content of floor in the 0- to 12-inch depth range below the coal seam and ultimate bearing capacity. Attempts to correlate ultimate bearing capacity and cohesive strength of immediate floor strata determined from borehole tests and confined compression tests were generally unsuccessful.