Lawrence Berkeley National Laboratory

This paper provides a comparative discussion of coupled hydromechanical processes in three different geological formations: crystalline rock, plastic clay, and indurated clay. First, the important processes and associated property characteristics in the three rock types are discussed. Then, one particular hydromechanical coupling is brought up for detailed consideration, that of pore pressure changes in nearby rock during tunnel excavation. Three field experiments in the three rock types are presented and their results are discussed. It is shown that the main physical processes are common to all three rock types, but with very different time constants. The different issues raised by these cases are pointed out, and the transferable lessons learned are identified. Such cross fertilization and simultaneous understanding of coupled processes in three very different rock types help to greatly enhance confidence in the state of science in this field.