Geomechanics investigation in a multiple room and pillar mine

Abstract

Various stability analyses were conducted for the Panasqueira tungsten mine (Portugal), which operates a multiple room and pillar e:\.1.raction system. Mechanical tests with rock specimens with the shape of actual pillars were performed to measure their strengths, both UCS for pillar models and tensile strength of roof formations, including the corresponding size effects. Acoustic wave velocity measurements were also determined in the laboratory and in situ. Boundary and finite element analyses were undertaken to evaluate roof and pillar stability, as well as surface subsidence.

Main results of the research indicated that the mechanical properties of mine rocks and the presence of major faults have a definite influence on stope stability and surface subsidence. Also, it was shown that occurrence of tensile stresses into the immediate roofs of stopes is a prerequisite for their collapse, particularly in places of the mine where there is a superposition of failed stopes.