The swelling potential of weak rocks is crucial to assess in stability determinations of tunnels constructed for both infrastructure and hydropower. Among the institutions that are involved with extensive research on swelling rock material, the methodologies applied at three different European institutions are reviewed in this manuscript. XRD analysis and oedometer swelling tests are included as index tests at all three institutions whereby the adopted swelling test methodologies at all three institutions are grounded in the ISRM standards. Different mindsets in how to forecast the challenges related to swelling are, however, reflected in the boundary conditions of test procedures and the internal modifications on the test apparatus, the preparation procedure, and in the choice of specimen size/mass. This manuscript reviews the adopted methodologies and highlights the advantages and drawbacks on the testing approaches used. Two of the institutions rely on a general approach which is standardized, and the results are compared. It is highlighted that, both institutions have modified the ISRM standard and the methodologies represents two unique approaches. Institution 3 have a case-specific approach and no test data were available. However, the described methodology differs from the procedures at Institution 1 and 2. Important differences between the testing procedures are both discussed and exemplified by comparing the test results obtained from duplicate samples at two of the institutions.
It is important to determine both rock properties and rock mass behaviour that are representative for the in-situ conditions. Rock samples are usually extracted from the project area and sent to the laboratories for testing so that it is possible to characterize the mechanical properties of rocks. Different procedures are available, but oedometer tests are most frequently used methods to evaluate the swelling potential of rocks and clay materials [1, 6]. Some researchers have introduced comprehensive test methodologies to reflect in-situ condition of the rock material at a specific location. Hence, the prevailing methodology in the investigation of swelling behavior of rocks for tunneling projects vary between institutions, both in identification and in the quantification of potential swelling.