GPR survey for investigation in building foundations

Planning of restoration works on degraded buildings should be preceded by collection of detailed data on their engineering, geotechnical and geophysical characteristics. These data should concern the design of the building, its structural features and foundations, as well as the geotechnical and geological characteristics of the soil and rock formations interacting with its foundations. Moreover, if the building has instability problems (settlements, slope failure, seepage, soil collapse, sink-holes, etc.) or has an “old age” (oxidization of reinforcing steel bars, masonry degradation), data acquisition should be as non-destructive as possible, fast and extend all over the investigated area. In the data acquisition stage, nondestructive methods, such as Ground Penetrating Radar, are very useful and in many cases absolutely necessary, as demonstrated in the two case studies presented here. Geophysical and geological investigations were carried out on two buildings located in L'Aquila and Chieti (Central Italy) which have undergone strong differential settlements. These phenomena caused widespread damages, which were mitigated by consolidation works. For the planning of these works, GPR, and geological surveys were performed in the area. GPR investigations (1600,600 and 100 MHz frequency monostatic type antennas and 300 MHz frequency borehole antenna) enabled to determine the actual size, depth and location of the types of foundation and of underground infrastructures. Wells and local geological and structural survey and excavations allowed to integrate and to calibrate the GPR data.