Railway Improvement, New Taipei, Taiwan

The project located in Raifung, one of the safety improvement plans of Taiwan Railways Administration(TRA). They had to solve the problem of fines pumped upward into the ballast layer because the vibrational load of trains transferred to the excess pore water pressure.

The phenomenon of fines pumping has distorted the rail owing to the differential settlement, and seriously endangered the safe running of railway accordingly. TRA was looking for a durable solution with the safety and cost efficiency that is not only replacing the ballast but also increasing the bearing capacity of the base and subgrade.

Several geosynthetic materials were applied together to meet the requirements of the project. After Removing the polluted ballast in the initial stage and graded the level of subgrade, a layer of permeable ACETex^® PP woven geotextile was laid as a separator to obstruct the upward movement of subgrade fines. As function of ACETex^®, high tension strength of geotextile improves the bearing capacity of subgrade and diminishes the differential settlement. For the purpose of longer service life, a nonwoven geotextile that manufactured by continuous filaments covered on ACETex^® mainly protecting ACETex^® against the abrasion of ballast. Then a layer of ACEGrid® GG geogrid was put on the top of the nonwoven geotextile. The geogrid has high tensile strength and apertures to provide interlock effect with the ballast and reinforce the base layer of the railway. At last, clean ballast was backfilled to the original railway elevation once completed the aforementioned works.

These geosynthetics are performing well and eliminate the occurrence of fines pumping at present. TRA has utilized this integrated solution as their regular method to solve similar problems.