Untersuchungen über typische Verteilungsmuster von Trennflächen und deren Ausbildung unter ingenieurgeologischen Gesichtspunkten

Geological and engineering-geological investigations have been performed In the medium Siegen-Formation in the Ahr-river-valley since 1978. The objective was to establish relations between the geological structure of the rock mass and engineering-geological parameters.During a first study the occuring discontinuity planes could be genetically classified under lithological aspects into 9 groups. Starting with the appraised typical features of discontinuity planes and the numerically described relations between lithology, deformation and weathering of the rock-mass as well as the structural parameters, it was possible to establish regional criteria for the definition of homogeneous areas.Slopes in the Ahr-river-valley resemble the system of discontinuities whereas the different planes predominate according to their local characteristics. Also the size and the Variation of the individual rockfragments depend largely upon the geological parameters of the- respective homogeneous areas.In a second step of the research programme the geometry of the discontinuity planes within the different units and their mechanical properties have been evaluated. This study comprised a great number of roughness measurements both in the field and in the laboratory. First time, a new terrestrical-fotogrammetric method could be applied with sufficient accuracy.The measurements of the shear strength along discontinuity planes were performed according to BARTON (1973), a method which allows the determination of shear strength parameters of planes without coatings by simple laboratory and field tests. Basic relations between the diagenetic roughness of discontinuity planes and the relevant shear parameters could be established. The tilt- and pulltests of BARTON have been supplemented by frame-shear-tests. Considerable differences were found, obviouslycaused by the higher stress-level of the frame-shear-test, which distinctly inflicts the roughness of the planes. The restricted validity of the BARTON-formula was confirmed. Therefore, a new relation has been derived, considering the normal stress, which is better adapted at least to the paleozoic rocks of the Rhenish Mountains.A counter calculation of a rock slide in the research area based upon the probabilistic safety concept has produced fair evidence of the correctness of the established parameters.