GPR survey of the soil base for the foundation was carried out in order
to detect areas of low density of soil. GPR was used with a center
frequency of 400 MHz. The survey site was covered with a grid of GPR
profiles located in 1 meter increments. View of the foundation ditch:
One of the work moments of the GPR survey of the bottom of the foundation ditch:
The processing of GPR profiles obtained during the survey of the soil foundation was carried out in software system GEORADAR-EXPERT. Based on the results of an automatized analysis of the backscattering field, sections of the Q-factor attribute (the ratio of the center frequency of the spectrum of reflected GPR signals to the width of the spectrum) from which the 3D assembly was formed were created. Elevated values of the Q-factor attribute indicate the presence of relative low density of soil.
The figure below shows the horizontal cross-section of the 3D assembly, the result of averaging the attribute values in the depth range from 2 to 3 meters. Horizontal section is combined with the scheme of foundation ditch. Violet and green lines in the plan of the foundation ditch - the position of the GPR profiles.
The cross-section is colored according to the following color scheme:
Sectional areas filled with colors from blue to dark blue correspond to relatively dense soils, with a dark blue color corresponding to the most dense areas of the soil. Sectional areas filled with colors from yellow to dark red correspond to relatively low density soils, with a dark red color corresponding to the most low density soils.
The figures below show horizontal sections of a 3D assembly. First, the result of averaging attribute values in a depth range of 3 to 4 meters is shown, and then the result of averaging attribute values in a depth range of 4 to 5 meters.
The analysis of the cross-sections made it possible to conclude that the signs of low-density soil decrease with increasing depth. In other words, most of the loose soil is located in the immediate vicinity of the foundation ditch surface.