Ballasted track systems with rubberized asphalt coatings and related methods

Abstract

An example track system includes: a supporting structure; ballast supported by the supporting structure; a plurality of track ties supported by the ballast; a pair of rails supported by the plurality of track ties; and a layer of rubberized asphalt coating disposed as an interface between the ballast and the supporting structure, the rubberized asphalt coating having bituminous binder, crumb rubber particles, and small gradation hard rock aggregate; wherein resiliency of the layer of rubberized asphalt coating permits particles of the ballast in direct contact with the layer of rubberized asphalt coating to move elastically relative to each other while inhibiting abrasion of adjacent ones of the particles of the ballast against each other and against the supporting structure.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This utility patent application is a continuation-in-part of U.S. patent application Ser. No. 17 / 730,270, filed on Apr. 22, 2022, which claims the benefit of and priority to U.S. Provisional Application 63 / 186,483, filed on May 10, 2021, and U.S. Provisional Application 63 / 295,985, filed on Jan. 3, 2022, with the entirety of each of the aforementioned applications being incorporated herein by reference.[0002]This utility patent application also claims the benefit of and priority to U.S. Provisional Application 63 / 186,483, filed on May 10, 2021, and U.S. Provisional Application 63 / 295,985, filed on Jan. 3, 2022.BACKGROUNDField of the Disclosure[0003]The present disclosure generally related to transportation systems and, more specifically, to ballasted track systems as well as related methods.Description of the Related Art[0004]Since the introduction of concrete crossties after World War II, their application has been plagued by interface i...

AI Technical Summary

Benefits of technology

The patent text describes a problem in ballast track systems, where the hard bottom of the tie and the supporting stone ballast bed interface and cause issues with high unit pressures and contact loads. This results in ballast fouling, differential track subsidence, and higher maintenance costs. The text also mentions the use of under tie pads (UTP) in North America to address the issue, but the high cost of the UTP has limited its usage. The technical effect of the patent text is to provide a cost-effective solution to address the issue of ballast life and track maintenance in transit applications.

Problems solved by technology

Since the introduction of concrete crossties after World War II, their application has been plagued by interface issues between the hard bottom of the tie and the supporting stone ballast bed.

The issues are the result of two hard surfaces coming into repeated contact under high unit pressures generated by the high axle loads typical of North American railroading and heavy-haul railroads all over the world.

That is, over an order of magnitude greater than the typical calculations for the bearing loads on the ballast bed when using the Talbot formulae and accounts for the destruction of the ballast stone particles by impact, cleavage and wear, which reduces the nominal ballast gradation size rather quickly under heavy tonnage, generating fines and causing drainage issues at the same time.

As the stone particles become less angular from these causes, there is a greater tendency for the ballast to “churn”, causing faster degradation.

All this results in ballast fouling, differential track subsidence, short ballast life, and higher maintenance costs.

It should be mentioned that train-generated high-frequency vibrations are also a contributing factor, possibly substantial, to ballast degradation.

Train-generated high-frequency vibrations have been studied in France and Germany, where high-speed trains are common, but not much data has been obtained on this side of the Atlantic.

A primary reason that there is not much higher usage is the high cost; installing a UTP increases the cost of a concrete tie at the mill by 25% to 40%, depending on the type UTP used.

This is too big a premium to pay to use along entire lengths of rail, so the user railroads only tend to use UTP's in trouble spots.

Ballast life also tends to be problematic in transit applications such as those involving weak roadbeds, excessive vibration and / or noise.

Breakage and wear of ballast at the ballast particle / supporting structure interface, especially in the proximity of concrete ties, is oftentimes unacceptable.

This tends to occur because the ballast stone is hammered both top and bottom, resulting in rapid breakage and degradation.

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