Numerical stress initialization in geomechanics via the FEM and a two-step procedure

Abstract

The knowledge of the in-situ stress field in rock masses is crucial in different areas of geo-engineering, such as mining or civil underground excavations, hydrocarbon extraction, CO2 storage, hydraulic fracture operations, etc. A method for the numerical generation of the in-situ stress state is described in this paper, which involves two steps: 1) an estimate of the stress state at each Gauss point is generated, and 2) global equilibrium is verified and re-balancing nodal forces are applied as needed. While the re-equilibration step is a closed procedure based only on statics, the first estimate of the stress state can be done in a variety of ways to incorporate all the information available. In this paper, the various options available are discussed and compared, and a new alternative procedure is presented which is based on the Airy stress function. The performance of the various procedures is illustrated with a real application example.