Sisgeo measuring anchors are designed as an instrumented rockbolt; they are composed by four iron rods anchored every 1/4 of the grouted instrument length, a 38mm OD tube and a measuring head. Replacement of typical working anchors with measuring anchors on a cross section will enable the computation of stress diagrams around the tunnel. Readings are taken manually by a dial gauge or could be also automated by using vibrating wire displacement transducers.