Technology and determination of the applicability of stone blowing at the current track maintenance

Abstract

Grain composition of track ballast is in a narrow size range, which provides maximum volume of ballast voids of 30–60 mm for category 1 crushed stone, 25–60 mm for category 2 crushed stone with round sieves and 22.4–63.0 mm for category B crushed stone with square sieves. This range facilitates drainage and provides significant intra-ballast cavities for storing products of spalling and abrasion of particles of ballast material. All of these useful ballast functions are provided when the ballast is properly packed. The wider size range of ballast particles provides, in turn, increased strength and deformation resistance due to a denser arrangement of particles, but in this case the ballast has a smaller volume of voids. In the event of increased abrasion of the ballast, for example in the form of a shake, accompanied by the formation of fine particles (less than 0.01 mm), a decrease in the volume of the voids of the ballast prism can be critical for the drainage properties of the ballast.
The article presents the test results of experimental technology for surfacing of the track ballast — surfacing with stone blowing carried out by specialists of the JSC “VNIIZhT” and the RUT MIIT (“Tracks and track facility” Department) in 2018. In October 2017 comparative tests of surfacing for under-sleeper pads and stone blowing were carried out under the conditions of the Test Ring of the JSC “VNIIZhT” which is close to the actual operating conditions. Then, three sections were laid in the operational area of the Test Ring — two tested (with surfacing for under-sleeper pads and stone blowing) and one reference. The need to continue researching exactly the stone blowing technology arose due to the fact that in October 2017, due to climatic conditions (air temperature fluctuations to negative values), it was not possible to obtain force track profiles and clarify the migration factors of blown crushed stone into track ballast.
The test results confirmed the effectiveness of track surfacing with a stone blowing process. The use of new equipment allows improving this surfacing technology. As part of the tests, it was possible to find ways to counteract the migration of blown crushed stone into track ballast.