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About PENOPLEX / Transport construction / Railroads

For the past several years, PENOPLEX^® 45 boards have been widely used by the Ministry of Transport of the Russian Federation as a frost protection layer for the reconstruction of the track ballast prism.

The material was improved to meed the requirements of the Ministry of Transport and the boards now have specially prepared edges. The use of Penoplex boards was approved by the Ministry of Transport of the Russian Federation after a series of tests in the track laboratory of the MIIT, and is regulated by normative acts of the Department of Tracks and Structures of the Ministry of Transport of the Russian Federation:

• Technical directions for use of foamed polystyrene and geo-textile for increasing strength of the trackbed without removing railroad tracks and cross ties;
• Standard design and technologies for strengthening trackbed for preparing test tracks for opening high-speed traffic of passenger trains. Issues 1 and 2.

PENOPLEX^® boards have proven their effectiveness and are used by ten railroads of Russia: Vostochno-Sibirskaya, Sverdlovksya, Gorkovskaya, Zapadno-Sibirskaya, Severnaya, Oktyabrskaya, Dalnevostochnaya, Kujbyshevskaya, Krasnoyarskaya, and Moskovskaya. In addition, a structure using PENOPLEX^® boards was designed and is being used for providing waterproofing, sound proofing, and protection from mechanical damaging of railroad tracks of tray spans. This structure was used in 2002 for the construction of Ladozhsky railroad station in St.Petersburg and a railroad bridge near Verebie (Oktyabrskaya Railroad).

The main problem of railroads in regions with cold winter is the deformation of railroad tracks caused by frost heaving. At temperatures below freezing, ice lenses are formed in the body of the trackbed saturated with water. They cause uneven elevations in the track ballast prism and the tracks deforming them.

When the temperature rises during warmer seasons, the ice lenses thaw and turn into water, which decreases the strength of the soil. The supporting layers of the trackbed liquify and form a sediment. Over time, several freezing/thawing cycles cause a series of uneven changes in the level of railroad tracks forming a clearance. This causes deformation in the tracks, which lowers their reliability and safety.

The fact the the optimal speed of trains in Russia is 120–140 km/h increases the requirements for a reliable and safe operation of railroad tracks. In the areas that suffer from freezing/thawing cycles of the soil, the only way to meet these requirements is regular maintenance of tracks and lower train speeds.

The Ministry of Transport of Russia was actively engaged in providing solutions to this problem and studied the most effective modern methods of protecting railroad tracks from frost heaving. The Ministry studied the methods that had been used in the Russian Federation, as well as those used in Norway, Sweden, Austria, and Germany.

There exist several technologies for maintaining safety of railroad tracks:

• Complete replacement of frost heaving soils. This requires earth digging, removal, and replacement with high-quality coarse and semi-coarse grade sand. It is necessary to additionally strengthen the trackbed with shields in order to prevent soil movement. In addition, it is necessary to use auxiliary tracks during the period of reconstruction and remove large quantities of soil, which significantly increases the cost of reconstruction.
• Creating a frost protection layer of insulating material. Foamed polystyrene and asbestus concrete that were originally used for this purpose provided insufficient strength and service life.

Currently, one of the alternatives for increasing the strength of the trackbed (where efficiency is calculated as a sum of costs, technologies, and service life) is a method of using extruded foamed polystyrene as an insulating layer. This method was chosen as the most effective in the tested conducted by the Ministry of Transport, when there are difficulties in draining surface waters and in the zones of increased loads. Specialized railroad track repair machines, such as the RM-80 or the Samson, are used for this task. The machines allow for:

• working on the tracks using 6–8-hour windows in train schedules;
• simultaneous nonstop digging out, cleaning, and replacing of gravel;
• place insulant and replace track ballast at the same time.

This shows a high efficiency of this method. During the three years of the reconstruction of the Otyabrskaya Railroads, the Ministry of Transport was able to study the positive experience of using this technology. Now, this method is officially recommended for use at other railroads.

In addition, PENOPLEX^® is superior to all other types of insulating materials. Penoplex prevents soil from damaging because it does not absorb water and has better resistance to freezing, higher compression and bending strength, resistance to dynamic loads, and it does not decompose.

Property	Units	Requirements of the Ministry of Transport	Penoplex properties	Testing method
Density	kg/?³	35	38.6-50.0	GOST 17177-94
Compression strength at 5% linear deformation	MPa	no less than 0.45	0.5	GOST 17177-94
Max. bending strength	MPa	no less than 0.7	0.7	GOST 17177-94
Deformation under multiple dynamic load cycles	%	no more than 5.0	2.1	Special program
Water absorption in 24 hours, of the voluem	%	no more than 0.5	0.2	GOST 17177-94
Thermal conductance when moist	W/mK	no more than 0.04	0.036	GOST 30290-94
Length	m	no less than 4.0	4.0-4.5
Width	m	0.4-0.6	0,6
Thickness	mm	40-100	40-60

Water freezing in colder layers of soils and damages the tracks. Insulant boards, when placed at a depth of no less than 0.4 meters, prevent water from accumulating in water absorbing layers of the trackbed during rainy seasons, and decrease the depth of the frost line in the winter. The thickness of the insulant depends on climatic conditions, depth of the level of groundwater, condition of water drainage facilities, and id calculated so that it allows to drain the water completely from the frost level of frost heaving soils. The use of PENOPLEX^® boards changes the process of soil freezing. The frost line of the soil under railroad tracks that does not have insulating layers is deeper than that at the sides. This causes a shift of water from the sides to the trackbed in the winter, thus contributing to frost heaving. The frost line of the soil under railroad tracks that does have insulating layers is higher than that at the sides, which cause the water to flow away from the trackbed. This decreases the depth of the frozen layer of soil and lowers frost heaving. The soil sinks insignificantly, its density increases, and it does not become liquified during spring thaws.

The optimal price/quality ratio of PENOPLEX^® 45 allowed the Ministry of Transport of Russia to recommend it as the main insulating material for overhaul of railroads in Russia. Specialized construction equipment and machinery is used that allows for reconstructing the trackbed without removing the tracks. After gravel is removed, Penoplex boards are placed at a pre-calculated depth, in a certain order and configuration at different transition zones. Then the gravel is replaced. The use of specialized machinery allows to minimize stall times using only windows in the train schedule.

PENOPLEX^® 45 is a highly effective insulating material that offers excellent properties for the protection of soil from climatic changes and increases safety and service life of railroads.

Reconstruction of the trackbed with the RM-80 machine.