Estimating the influence of saturation on investigating fouled railway ballasts using ground-penetrating-radar

Ground - penetrating-radar, GPR, is one of geophysical and non - destructive method that uses radar pulses to investigate the difference of ground materials. This method uses electromagnetic radiation in the microwave band (frequencies generally from 10MHz to 2.6 GHz) of the radio spectrum and detects the reflected signals from subsurface structures. A GPR transmitter emits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivity, it may be reflected or refracted or scattered back to the surface. The electrical conductivity of the ground, the transmitted center frequency, and the radiated power all may limit the effective depth range of GPR investigation. Dry sandy soils or massive dry materials such as granite, limestone, and concrete tend to be resistive rather than conductive, and the depth of penetration could be deeper. In moist and/or clay - laden soils and materials with high electrical conductivity, penetration may be as little as a few centimeters. However, in experienced cases it was not significant to tell the clear interfaces between different ground materials. A series of laboratorial tests of scanning pure/mixed soil w/o water using GPR was performed. The purpose of this study is to establish a chart illustrating the relationship of materials versus GPR reflecting images.