Application of Geology to Tunneling Problems

Geological examination of tunnel sites prior to and during tunneling operations has become established procedure. The geologist should study and appraise carefully all surface and subsurface features having any bearing on the engineering problems associated with the drawing of the tunnel. Particular attention should be given to the following: (1) Internal structures, physical characteristics, and distribution of the rocks and overburden; (2) secondary structural features such as folds, faults, and joints; (3) chemical alteration of the rocks; and (4) the distribution and flow of ground water. Suggestions for overcoming or minimizing difficulties presented by caving ground and other undesirable conditions in tunnels are given, and the causes and effects of caving in selected examples are discussed in detail.