 Proceedings of Engineering and Technology Innovation , vol. 4, 2016, pp. 49 - 51 49 Using Ground-penetrating Radar to Promote the Investigating Efficie ncy in Mud Pumping Disaste r of Railways Chihping Kuo 1,* , Chihhao Hsu 1,2 , Yenyu Chen 3 , Chinwei Wu 1 , Hongyi Wang 1 , Dewei Chen 1 , YiXuan Lin 1 1 Department and Institute of Civil Engineering and Environmental Informatics, Minghsin University of Science and Technology, Hsinchu, Taiwan. 2 Taipei Engineering Division, Taiwan Railways Administration, MOTC, New Taipei City, Taiwan. 3 SamHo Technology & Engineering Co., LTD, New Taipei City, Taiwan. Received 20 January 2016; received in revised form 15 February 2016; accept ed 03 March 2016 Abstract Currently about 85% of the railway structure is constructed traditionally in Taiwan, which means the foundation of railways is composed by in-situ soil materials and covered by ballast, sleepers and tracks. The rail is continued by fis h- plates and then bolted. While train passes here, the deflection caused by repeated loads. The repeatedly force transfers through ballast to the saturated foundation, may create vacuum to draw phenomenon, called pump effect or mud pu mp- ing. It could lead to serious train derailment cap- sized. 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. Using non-destructive testing techniques (ground-penetrating radar) to inspect the quality of rail bed is widely in foreign. However, d e- tecting the distribution of mud beneath rail is an attractive subject here. By the usage of mention technology in this research, this technology is expected to be promoted. This study has been agreed by the official administration, Taiwan Railway Bureau, to be carried out in Nanwan branch in Hsinchu by using ground-penetrating radar. Co mparing with the visual inspection results, the mud pumping can be verified. Where most serious mud pump- ing phenomenon observed was open to prove the function. The study is expected to launch the road bed structure further rehabilitation plans and preventative ma intenance engineering. Further- more, cost due to misjudgment is expected to be saved and traffic safety improved. Keywor ds : mud pumping, railway bed, ground-penetrating radar, disaster 1. Introduction 1.1. Phenomena and Effect of Railway-bed Mud-pumping The general structure of ra ilway bed is lay- out in Fig. 1. The loading fro m tra in transfers to the subsoil of g round through rails, sleepers, ballasts , and subballasts. Ballast plays important role in the loading transferring work. The load- ing has to be uniformly and equally transferred by ballasts. The rainfa ll requires to be drained rapidly by ballasts as well. When the ballasts were filled by subballasts , it would reduce the function of ballasts. Subballasts generally is used for adjudging the required elevation of rails and composed by mixed soils. In most cases , fine materia ls like silts or clays are more wel- come than granulated ones like sands or small gravels due to the budgets. Fig. 2 shows the common phenomena observed in railway. The mud covers the sleepers and ballasts as pumping fro m subballasts . A serious issue is after the pumping occurred; the materia ls did not flow back to subballasts. Therefore the cavities exist inside the subballasts and induce the differentia l settlements for sleepers and rails. A potential disaster consequently threatens the safety of train’s traffic. Inspecting by naked vision is the traditional and now-used method for the inspectors in Taiwan Ra ilway Bureau in Ta iwan. Besides, they can only discover the cases that already pumped out the ballasts. The distributions and * Corresponding aut hor. Email: picnic.kuo@must.edu.tw Proceedings of Engineering and Technology Innovation , vol. 4, 2016, pp. 49 - 51 50 Copyright © TAETI shapes of pumping or cavit ies are also difficult and impossible to be discovered in this way as illustrated in Fig. 3. A more effic ient and con- venient method has to be developed and pro- posed in this paper. Fig. 1 General structure of railway bed Fig. 2 Mud pumping observed in the Neiwan branch line in Hsinchu (2016.01.05) Fig. 3 How pu mped materia ls distribute and form inside the subballasts requires more efficient method to be investigated and inspected 2. Method Ground-penetrating radar (GPR) is a geo- physical method that uses radar pulses to image the subsurface. This non-destructive method uses electromagnetic radiat ion in the mic rowave band (UHF/ VHF frequencies) of the radio spectrum, and detects the reflected signals from subsurface structures. GPR can have applica - tions in a variety of media, including rock, soil, ice, fresh water, pavements and structures. A GPR transmitter e mits electromagnetic energy into the ground. When the energy encounters a buried object or a boundary between materials having different permittivit ies, it may be re - flected or refracted or scattered back to the su r- face. A receiv ing antenna can then record the variations in the return signal. Dry sandy soils or massive dry materia ls such as granite, limestone, and concrete tend to be resistive rather than conductive, and the depth of penetration could be up to 15m. In moist and/or clay -laden soils and materia ls with high e lectrica l conductivity, penetration may be as little as a few centimetres. Ground-penetrating radar antennas are generally in contact with the ground for the strongest signal strength. [1] Generally GPR are adopted to check the el- evation of subballasts and subsoils. However, the mothed is not popular in Ta iwan. In this study, a GSSI 400MHz antenna with SIR-20 server were adopted to scan a 40m long railway. This section was selected for varies kinds of mud pu mping occurrences observed here. Fig.4 shows the inspection work o f pu mping pe r- formed by the authors. Fig. 4 Inspection for mud pumping in the Nei- wan branch line in Hsinchu (2016.01.05) 3. Results and Discussion The results from GPR scan shows the dis- tributions and shapes of pumped materia ls inside the ballasts and subballasts . The blue line indi- cates the boundaries of pumped materials . Co mparing with the pu mping materia l surface that has pumped out the ballasts, the distribution of observed by vision and GPR are co incided. The depth of pumping material boundaries were also identical and proved after opening the bal- lasts as shown in Fig. 6. Using GPR to scan and inspect mud pumping is firstly performed in Taiwan. The result shows the boundaries of pumping materials can be estimated. 縱向斷面 A C B Section of traffic direction 橫向斷面 A C Cross section Hill-shape??? Mushroom-shape??? Proceedings of Engineering and Technology Innovation , vol. 4, 2016, pp. 49 - 51 51 Copyright © TAETI Fig. 5 The pattern of GPR scans and indicates the distributions and shapes of pumped materials inside the ballasts Fig. 6 The boundaries of pumping materials were found by opening the ballasts Acknowledgement Financia l support fro m Min istry of Science and Technology (MOST 104-2622-M-159-001 -CC3) is much apprec iated. Study area was provided by Taiwan Ra ilways Administration, MOT C. Re lated technique was provided by Sa mHo Technology & Engineering Co., LTD. Their kindly helps are very much appreciated. References [1] “Ground-penetrating radar,” https://en.wikiped ia.org/wiki/Ground-penetrating_radar, May 26, 2016.