GEOELECTRIC AND ELECTROMAGNETIC MEASUREMENTS ON A DOMESTIC WASTE SITE

摘要

The synthetic radargram in figure 6 shows that minor fissures in the clay liner cannot be detected with GPR even if the soil was homogeneous as assumed in this model. Comparing figure 6 with figure 5 one can conclude that a dislocation of Δz= 0.30 m or more should be visible in the field data. Since there is no such sign of disruption or slip in the measured profiles the leakage cannot result from a dislocation of that size. Most of the points with a locally weaker or disrupt signal in figure 5 show an overlying diffraction hyperbola. Therefore these points cannot necessarily be interpreted as a rupture or greater fissure in the gravel or clay layer. The disturbing effects of such diffractions may result in signal weakening as well. Nevertheless some interesting spots of the GPR measurements require further investigations. Those are points with a loss of signal power without an overlying diffraction hyperbola or similar disturbing effects. The main problem of the geoelectric data is the non-uniqueness of the models: There always exist several models with a similar rms error for one profile. There is no obvious hint of a probable dislocation or other leakage from the geoelectric techniques used. The described methods did not show any definite reason for the leakage nor an exact location in the mineral clay liner of the lysimeter for the source of the leakage. Yet some spots can be specified that may hint to a possible leakage and that should be examined more closely to gather further informations. Taking into account the synthetic radar data it can be assumed that the leakage is owed to microfissures probably occuring during a very dry period. Such fissures could not be detected either with GPR or with geoelectric measurements used in this case. In addition, both methods (geoelectrics and GPR) point to a lower soil water content at the edges of the lysimeter.