This paper provides a review of hydromechanical (HM) couplings in fractured rock, with special emphasis on HM interactions as a result of or directly connected with human activities. In the early 1960s, the coupling between hydraulic and mechanical processes in fractured rock started to receive wide attention. A series of events-including dam failures, landslides, and injection-induced earthquakes-were believed to result from HM interaction. Moreover, the advent of the computer technology in the 1970s made possible the integration of nonlinear processes such as stress-permeability coupling and rock mass failure into coupled HM analysis. Coupled HM analysis is currently being applied to many geological engineering practices. One key parameter in such analysis is a good estimate of the relationship between stress and permeability. Based on available laboratory and field data it was found that the permeability of fractured rock masses tends to be most sensitive to stress changes at shallow depth (low stress) and in areas of low in situ permeability. In highly permeable fractured rock sections, fluid flow may take place in clusters of connected fractures that are locked open as a result of previous shear dislocation or partial cementation of hard mineral filling. Such locked open fractures tend to be relatively insensitive to stress and may therefore be conductive at great depths.Because of out the great variability of HM properties in fractured rock, and the difficulties in using laboratory data for deriving in situ material properties, the HM properties of fractured rock masses are best characterized in situ.

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Nearly 1500 stress orientation determinations are now available for Europe. The data come from earthquake focal mechanisms, overcoring measurements, well bore breakouts, hydraulic fracturing measurements, and young fault slip studies and sample the stress field from the surface to seismogenic depths. Three distinct regional patterns of maximum compressive horizontal stress (SHmax) orientation can be defined from these data: a consistent NW to NNW SHmax stress orientation in western Europe; a WNW‐ESE SHmax orientation in Scandinavia, similar to western Europe but with a larger variability of SHmax orientations; and a consistent E‐W SHmax orientation and N‐S extension in the Aegean Sea and western Anatolia. The different stress fields can be attributed to plate‐driving forces acting on the boundaries of the Eurasian plate, locally modified by lithospheric properties in different regions. On average, the orientation of maximum stress in western Europe is subparallel to the direction of relative plate motion between Africa and Europe and is rotated 17° clockwise from the direction of absolute plate motion. The uniformly oriented stress field in western Europe coincides with thin to medium lithospheric thickness (approximately 50–90 km) and high heat flow values (>80 m W/m2). In western Europe a predominance of strike‐slip focal mechanisms implies that the intermediate principal stress is vertical. The more irregular horizontal stress orientations in Scandinavia coincide with thick continental lithosphere (110–170 km) and low heat flow (<50 m W/m2). The cold thick lithosphere in this region may result in lower mean stresses associated with far‐field tectonic forces and allow the stress field to be more easily perturbed by local effects such as déglaciation flexure and topography. The stress field of the Aegean Sea and western Anatolia is consistent with N‐S extension in a back arc setting behind the Hellenic trench subduction zone. The stress field is influenced in places by regional geologic structures, e.g., in the Western Alps, where SHmax directions show a slight tendency toward a radial stress pattern. Not all major geologic structures, however, appear to affect the SHmax orientation, e.g., in the vicinity of the Rhine rift system horizontal stress orientations are continuous.