Geotechnical Problems Caused by Abandoned Stone and Clay Mining Areas

bánya (Budapest, Hungary) was the main source of building materials at the end of the XIX. Century. At that time it was a suburb but the growth of the city reached it in the next century. Later most of the open pits were filled by waste. It causes severe geotechnical problems on the residential areas and besides there is a continuous need the use the filled pits for building purposes. The geotechnical solution of the problems is rather easy but expensive. In most cases it would be enough to know the maps of the pit at the time of the closure but unfortunately most of them were lost. In other cases, mostly at open pits filled by waste the compaction and the decomposition of the organic materials cause problems over a long period. The waste is highly inhomogeneous, conventional geophysical methods, supposing layers, can’t image the pits with satisfactory results. Seismic tomography using different wave-types was used to map the outlines and the structure of the backfilled pits. Experiments were made to detect the gas content of the decomposed waste by using Vp/Vs ratio.