Multi-frequency GPR sounding

The GPR sections obtained along the same profile at frequencies of 150 MHz, 900 MHz and 1.5 GHz

GPR sounding at different frequencies gives significantly different results when working out the same profile. Depending on the energy and frequency of the sounding pulse, the depth of penetration of the signal and the peculiarities of its reflection from the boundaries of the soil massif with different physical properties, lithology and the degree of water saturation vary significantly. Interpretation of different frequency GPR sections gives mutually complementary information about the structure and properties of the studied soils.
The presence of surface diffracting objects near the profile, especially metal structures, has a significant impact on the view of sections obtained with low-frequency dipole antennas. In the left part of the upper section the traces of intense diffracted waves from the nearby metal pillars can be seen.

GPR vertical section and horizontal cross section of the RMS-amplitudes according 3D GPR sounding on the frequency 900 MHz

GPR sounding on a dense network of profiles allows to create a data cube, represented by samples of amplitudes of the reflected signals, which can be transformed into cubes of different dynamic parameters of the reflected signals. Maps of these parameters distribution on the horizontal sections of the cube give an idea of the distribution of various inhomogeneities in the soil array, affecting the passage and reflection of electromagnetic pulses. One of the most significant factors affecting the amplitude of the reflected sounding pulse is the degree of water saturation of the soil. It is possible the areas of high amplitude reflections track the channels of groundwater seepage, which occurs suffusion of the foundation soil and removal of fine fractions of sand into the area of unloading.
These horizontal sections show the shape of the filtration channel in sandy soil at a depth of about 0.5 m under the paving of the embankment of the cargo terminal of the port. The channel is formed at place of surface water infiltration near the under crane girder and unloaded in the river at the quay wall. The low amplitude reflections along the under rail beam at a depth of 12 cm correspond to voids and softening, formed as a result of the surface subsidence of the foundation soil.