The elasto-plastic material behavior of rock anchors with hardening and its application in mining

摘要

For the systematic anchoring of the roof in potash and salt mining in Germany today, anchor steel varieties that have a large yieldingness are used. The numerical implementation of this "plastic deformation reserve" after exceeding the elastic tension limit is not provided by default in the Itasca codes FLAC and UDEC. Therefore, specific FISH routines were developed to simulate this tensile hardening. With the help of these routines any characteristic anchor curve can be implemented. The behavior of a special anchor steel (mining - GEWI-steel ST 450/700) widely used in salt mining that can be described as elasto-plastic with hardening, was implemented. By means of two examples and comparison with the default, perfect elasto-plastic anchor behavior, it is shown that the anchors bear much higher deformations until reaching the tensile strength limit. Considering rheological rock mass behavior, such anchors can fulfill their function for much longer times. In general, the detailed consideration of the characteristic anchors curve instead of using the default perfect elasto-plastic behavior, resulting in significant other and more realistic load-displacement patterns for both the anchors and the surrounding rock mass.