A site with shallow karst bedrock is characterized for engineering purposes by examination and testing of rock samples and by classification of the rock mass according to the RMR system. For all of the rock samples, an RMR of 65 was assigned. For the cave roof conditions, an RMR of 50 was assigned. On the basis of the RMR values, a failure criterion (or model) was established using the Hoek-Brown failure criterion. The authors believe that this is the first published application of this approach for evaluation of naturally occurring openings in rock.