MODELING OF STATIC MINING SUBSIDENCE IN A NONLINEAR MEDIUM

Applications of the conventional finite element method to problems of mining subsidence can result in excessive expense, particularly when nonlinear constitutive stress/strain relations are used for the geological medium. An alternative finite element method is proposed which captures the essential characteristics of subsidence observed both in more sophisticated finite element programs and in the field. The alternative method treats the overburden with classical beam theory with the inclusion of shearing deformation. The nonlinear axial response of the pillars as well as the nonlinear response of any backfill that may be present is also modelled. Flexural and bending modes of deformation are included for the pillar and backfill media with classical beam theory. Shearing deflections are also included for these structural members. The development of the constitutive relations, the implementation of the constitutive relations in the computer program and the numerical algorithm for the problem solution are presented. An example problem in subsidence is presented to illustrate the potential of the computer program. Computer cost for the example problem clearly demonstrates that the alternative method for analysis of subsidence problems deserves consideration