Detection of subterranean cavities and anomalies using multichannel analysis of surface wave
Hossein Rahnema, Leila Ehsaninezhad, Fatemeh Dashti, Ghasem Talebi
Abstract
Both underground cavities and anomalies are important issues which may cause damage to ground strata and subsequently to their overlaying structures due to subsidence and excessive settlement. Thus, the first step of stabilising the ground and preventing undesired damages is detecting these cavities. In this paper, multichannel analysis of surface waves (MASW) test as a general surface wave method is utilised for obtaining the properties of the ground and the coherence function of two adjacent signals to establish an approach for detecting multiple underground anomalies. In this regard, MASW tests were performed in five numerical models of homogeneous half-space with multiple cavities. The extent of the signals’ coherence of acquired seismic data of each couple of adjacent signals was plotted to delineate the cavity and anomaly location. The results of coherence values showed a distinguishable-coherence zone in the spectrum. Two main categories of cavities and buried concrete masses were investigated via the coherence function, indicating a decline in the cavity position and a rise in the concrete mass position. Eventually, to test the validity of the method, two sets of real data were employed. The results of both numerical and experimental data showed the accuracy of the method.