The contribution summarizes the experiences from intensive dam site in-vestigations in Germany during the last years and will show how different investiga-tion techniques can be used not only for rock, but also for porous mass concrete struc-tures. These structures intensively have been used in German waterways for weir sys-tems and river locks at the beginning of the 19th century. The maintenance and renova-tion of these structures, due to aging, nowadays becomes more important and obvious-ly will last for several decades. It therefore may turn into a major new area of opera-tion also for civil-engineers with a background in rock- and soil-mechanics. Two site investigations for an earth- and rockfill dam, with dam heights of 20–35 meters, including also a rare direct comparison of refraction seismic and geoelectric resistivity imaging are introduced, an example of a typical porous mass concrete struc-ture (weir-system) is given. Results and comparison of different drilling techniques in rock, concrete, borehole imaging (scanning), water-pressure- and grouting-tests and experiences on testing different fineness grades of ultrafine cements during grouting are presented. Results of grouting in respect to sealing, increase in compressibility and durability of porous mass concrete as well as results of anchor pile tests and tests with rein-forcement concrete steel bars for anchoring are shown.
The planning region of the rockfill dam is assigned to the gneiss formations of the ore mountains in Saxony. Typical is a metamorphic rock complex as basement with weathered rock, Holocene fluviatile and quaternary sediments as overlying strata with a thickness up to about 8 m in the valley floor. For both sites comprehensive ground investigation programs were carried out in two stages including vertical and inclined core drilling up to about 25 m below the dam foundation.