Evaluating Fouled Railway Ballast Using Ground-Penetrating-Radar

Soil pumping phenomena comprise a wide issue in traditional railway structures. A newly built railway structure from the top down contains rails, slippers, ballasts and soil layer foundation. Currently about 85% of the railway structure is constructed traditionally in Taiwan as mentioned. With the infiltration of rainfall or groundwater, the soil foundation will become saturated. After repeated loading from passing, trains the soil will become even more saturated and squeezed into the voids inside the sub-ballasts or ballasts. The pumping effect is then initiated and the pumping paths start to scurry. The repeatedly force transfers through ballast to the saturated foundation, may create vacuum to draw phenomenon, called pump effect or mud pumping. It could lead to serious train derailment capsized. Present mud pumping detection method has to be performed during the non-operating time at night by visual. However, this approach may have omissions and shortcomings perspective concerns, and slow to find disasters during the rainy season. According to previous studied result, the pumped mud is characteristic of being quasi-liquefied, denser, and with exceed pore-water pressure. The loading from trains cause dynamic force to rise the pore-water pressure. Adopting the feature, a tubing-floater device is proposed to install on the interface between ballasts and soil layer foundation. No matter the ballast sinks or mud pumping up, the floater will be raised due to the pressure generated in the tube. The laboratorial experiment has been performed to prove the feasibility of the idea herein.