In-situ Stress Field at the Pea Ridge Mine.

摘要

The in-situ stress field was determined,using the overcoring technique,at two underground sites at the Pea Ridge Mine, Sullivan,Missouri. At one of the sites in magnetite,the three dimensional stress field showed the largest principal stress to be compressive (-4564psi),nearly horizontal and closely parallel to the strike of the orebody. The smallest principal stress was also compressive (-2047psi) and nearly vertical. Considerable difficulty was experienced in drilling porphyry rock at the second test site in the host rock. Only one hole was drilled at this site. The secondary principal stresses obtained in the porphyry are -9464and -4945psi,respectively. The test site in magnetite is located at a depth of 2505feet whereas the site in porphyry rock is at 2475feet. The vertical stresses due to overburden loading at these sites are -3590and -2782psi,respectively. Field determined values of the vertical stress are -2207and -5098psi,respectively. The variance between the two sets of values is most likely attributable to the orebody formation and the differences in the modulii of the host rock and the orebody.