The method to get clear image for the railway ballast structure with the Ground Penetrating Radar Horn Antenna

In the realm of railway infrastructure, the safety of railway road base structures is of paramount importance. A conventional railway raod base is composed of three distinct layers: square cement sleepers positioned at the top, ballast situated in the middle, and undisturbed bedrock or soil at the base. Railway roadbase are prone to a variety of structural challenges that can manifest differently based on their geographical context. In excavated railway sections, particularly those located in limestone regions, the occurrence of karst cracks and cave formations is a significant concern. Such geological phenomena may lead to the ballast stones falling into underlying cavities, thereby diminishing the thickness of the ballast layer. This reduction can adversely affect the bearing capacity of the railway sleepers, thereby compromising safety during train operations. Additionally, during the summer months, ballast may become saturated with rainwater, resulting in the formation of mud and mud overflow to the ground surface; conversely, in winter, the volume of ballast may increase due to ice heaving, leading to deformation of the railway track and square cement sleepers. Both scenarios pose safety risks for train operations and necessitate a thorough investigation of the ballast structure with ground penetrating radar.

To assess the condition of the raiway ballast structure, a Ground Penetrating Radar (GPR) system, along with three sets of air coupled antennas operating at a center frequency of 1.0 GHz, was employed. The antennas were strategically positioned at the front of the train, elevated 45 cm above the square cement sleepers, and arranged on the left, center, and right sides of the railway track. The GPR system successfully detected the railway cement sleepers and ballast structures, producing a two dimensional longitudinal profile for each antenna. The hyperbolic reflections generated by the cement sleepers were pronounced, which interfered with the emitted signals from the ballast, obscuring the ballast interface. Data processing was performed using a specialized local removal curve algorithm, which utilized a raw profile to subtract the local curve profile of the square cement sleepers, thereby eliminating the influence of the square cement sleepers. This data processing procedure resulted in a continuous reflection signal from the ballast layers, allowing for the identification of water distribution in water-bearing areas, variations in ballast thickness, and the structural characteristics of the railway subgrade and ballast layers in limestone regions. The Ground Penetrating Radar equipped with a horn antenna was utilized for scanning the railway ballast, yielding ballast clear reflection signals when combined with the specialized local removal curve method, thereby enhancing railway safety.