Back-analysis of a Rock Wedge Instability in the Ancient Parian Underground Marble Quarry

The existence of multiple families of joints within the rock mass and the degradation of its properties create an additional risk of the collapse of peripheral rock wedges within a tunnel. Identifying and analyzing removable wedges is the first step in evaluating underground excavation safety. Then, the computation of the identified removable rock wedge’s safety factor (SF) follows. For this purpose, an analytical technique is applied for estimating safety factors in cases of falling or sliding wedges. The most dangerous wedge is identified by block theory, in which the geometric rules to locate removable wedges were implemented with the contribution of stereographic projections. The results, derived from the procedure above, are evaluated with Rocscience’s Unwedge software. SF calculation is made by using active/passive forces method for to define the strength properties of the famous marble of Parian Marble based on failed tetrahedral wedges in the ancient quarry in Nymphs. This paper aims to identify potential failure zones in this underground quarry using basic rock mechanics principles to estimate the necessary measures.