The use of a surface gamma-neutron gauge to explore compacted soil layers

Surface gamma-neutron gauges have been used to evaluate soil physical prope rties, mainly soil bulk density. However, their use for compacted soil laye r detection is still not well understood. In this work, a surface gamma-neu tron gauge was used to identify the presence of compacted layers in soil pr ofiles. Variations of the gauge response were also investigated for layers located at different depths. The results showed that although this type of gauge yields an average value of the densities found along the gamma-ray pa th, the use of an algorithm permitted the transformation of gauge measureme nts into layer density values, which were in good agreement with gravimetri c measurements. The application of the algorithm was found to yield the bes t results when there was a large difference in density between the compacte d layers and the medium around them.