ABSTRACT
In mechanized rock excavations using Tunnel Boring Machines (TBM’s) the contact of the disc cutters with the rock precedes every other work like mucking and support. Penetration into the cohesive/frictional ground by the tip of a disc cutter subjected to a given thrust force can be achieved only a fraction of a cm at a time instant. In a backward analysis if cutting processes in rocks are properly registered and analyzed they give valuable information on the mechanical properties of the heterogeneous rock masses like strength, deformability, index properties such as abrasivity and hardness, or physical properties like content in abrasive or clay minerals. It is evident that a proper backward scheme may lead to a “smart” rock cutting process. On the other hand, the forward problem is the optimum design of cutting discs then of the cutting head and finally of the operational parameters of TBM’s under a given heterogeneous and “opaque” geomechanical environment. In order to achieve both aims the logical step is to study first the mechanics of a single disc cutter penetrating and cutting the rock and then compose the whole response model of the cutting head of a boring machine. Before the outset of the excavation of a TBM several geotechnical and geological data are collected along the tunnel “corridor”. This data should be interpolated along the planned tunnel axis. This interpolation should be done on a 3D grid of the geological model around and along tunnel axis. The Geostatistical approach accompanied with computer aided design tools provide the mathematical and the geometrical frames needed for the interpolation of spatially or temporally correlated data from sparse spatial sample data. Then it is possible to correlate the TBM performance with the geological-geotechnical conditions at regular intervals along the tunnel and extract valuable information regarding the former issue. Herein, we are going to display the above concepts and tools with an example case study.
