Track Geometry
What causes mud-pumping?

Where mud pumping occurs if left untreated it is likely to result in problems with track geometry making speed restrictions necessary and increased maintenance. So what causes mud-pumping in railroad trackbeds?


Water penetrates the trackbed, moving easily through the free-draining ballast until it meets the subgrade. In many areas the subgrade will be highly permeable, for example fissured rock and sandy soils so drainage is good and the water moves away easily. Where subgrades are less permeable, such as where clays and silts are present, the original construction will often have used an interlayer of crushed, well graded aggregate to separate the ballast from the subgrade.

If no aggregate interlayer was used the ballast will be directly on the subgrade. Where it is present, the interlayer may have weathered and degraded, or may not be adequate to protect the subgrade especially under todays heavy axle loads.


Where clay has been used to form an embankment the centre can become compacted over time due to the passage of trains. This renders it impermeable, and also forms a trough along the embankment which is difficult to drain.

Slurry Formation

Fine particles can derive from the subgrade or the weathered interlayer, and it is these fine particles combine with water to produce a highly mobile, viscous slurry. Passing traffic imposes dynamic loads through the trackbed construction putting the slurry under high pressure, then as the load passes a suction force develops under the ties. It is the cyclic nature of this load that creates the pumping action which squeezes the slurry up into voids in the ballast.

Once contaminated with the slurry the ballast is weakened, and drainage is inhibited. This leads to rapid track settlement and consequently deterioration in track geometry. In more advanced stages the track becomes impossible to maintain and ballast renewal is required. Typically ballast deterioration due to trafficking would be expected to last 1000 MGT, but where mud-pumping is left untreated this can be reduced to less than 100 MGT.

Preventing Mud Pumping, Ensuring Track Stability

Comprehensive Support Delivers Trackbed Performance

At GEOfabrics, we provide technical support to help you get the most out of TrackTex and address the cause of mud pumping. This ensures the stability and performance of your tracks. Our team of experts utilizes advanced techniques and technologies to deliver effective solutions tailored to your specific needs

Professional Development Hours

GEOfabrics continuing education sessions provide technical training on specifying and using TrackTex. These sessions contribute to PDH hours.

Trackbed Stabilization

Geosynthetics are widely used as a way to improve ballast performance under railways. GEOFabrics RK4 is a geocomposite comprising a stabilizing geogrid bonded to our RK1 needlepunched non-woven sep...

Symptoms of Mud Pumping

The symptoms of Mud Pumping are similar to those of life expired ballast, i.e. wet spots appearing at the surface of the ballast accompanied by rapid deteriorating of track geometry. However, from ...
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