Railroad track bed using injection materials and method therefor

In a railroad track bed, an injection layer is formed between the railroad ties and the raodbed so as to protect the latter. The injected layer is composed of an injection material injected through openings formed in the tie. The injection material has a viscosity below 30 poise at a temperature not higher than 200.degree. C. before hardening, and when hardened it has a compressive stress at 10% strain of 0.4 to 30 kg/cm.sup.2 at a compressive strain rate at 40.degree. C. of 1.5% per minute.

BACKGROUND OF THE INVENTION 
This invention relates to injection materials for a railroad track bed in 
which an injected layer is formed between the railroad tie and the 
roadbed. 
In recent years, the increase in the volume of railroad transportation has 
been giving rise to a correspondingly sharp increase in the frequency of 
railroad stock usage, resulting in an increased frequency of maintenance 
work for the track, in particular, the roadbed. The greater the frequency 
of train passage, the shorter the time allowable for the maintenance work, 
and so it has become necessary to provide beds which can contribute in 
labor-saving in connection with roadbed and track maintenance work. To 
this end, there have been studies of various systems which are believed 
capable of replacing the conventional ballast roadbed; for example, one 
proposal is the provision of a concrete roadbed another the use of an 
integral formation in a ballast roadbed. However, labor saving of 
maintenance work has not yet been fully attained. 
SUMMARY OF THE INVENTION 
It is an object of the invention to provide a railroad track bed for which 
the cycle of maintenance work is prolonged. 
Another object of the invention is to provide an injection material which 
is easily injected onto the roadbed and has a good working property. 
A further object of the invention is to provide an injection material which 
is hard to the extent that it does not undergo a great deformation against 
compressive stresses and which is soft to the extent that it absorbs 
vibration. 
According to a feature of the present invention, there is provided a track 
bed having an injected layer between the roadbed and the ties mounted 
thereon. The injected layer serves to uniformly disperse various stresses 
caused by the passage of a train so as to mitigate the impact force 
against the roadbed and protect the latter, whereby the cycle of 
maintenance work can be prolonged. 
According to an embodiment of the present invention, the injection material 
used with the track bed in which a layer of the injection material is 
formed between the tie and the roadbed preferably has a viscosity below 30 
poise at a temperature not higher than 200.degree. C. before hardening, 
and when hardened it preferably has a compressive stress at 10% strain of 
0.4 to 30 kg/cm.sup.2 at a compressive strain rate at 40.degree. C. of 
1.5% per minute. 
Other objects, features and advantages of the invention will appear more 
fully from the following description and from the accompanying drawings.

DETAILED DESCRIPTION OF THE INVENTION 
We shall now describe the invention with particular reference to the 
accompanying drawings. Rectangular ties 10 made of concrete or other 
material are arranged side by side at regular intervals on a ballast 
roadbed 12 composed of crushed stone, etc. Rails 14 having an I-shaped 
section are fixed on the ties 10 by means of a clamping device 16 made of 
iron or the like. The clamping device 16 also acts as a washer for the 
rail 14. The tie 10 has openings 18 in the form of an inverted circular 
truncated cone, for example, the top is 8 cm in diameter and the bottom is 
6 cm in diameter. Through these openings is injected a fluid injection 
material. The injected fluid material hardens as the time goes by to form 
an injected layer 20. 
The injected layer 20 in such track structure serves to uniformly disperse 
various stresses in the roadbed lower structure 12, which stresses occur 
when a train passes and are transmitted through the tie 10, and at the 
same time it also serves to absorb as much vibration as possible which is 
conveyed through the tie 10 to the roadbed 12 so as to mitigate any impact 
force against the roadbed 12 and protect the latter, whereby it is 
possible to minimize the abrasion of crushed stones and prolong the cycle 
of maintenance work. 
Injection materials for the injected layer 20 should have specific physical 
properties. That is, it is undesirable for them to undergo greater 
deformations than required throughout the year against compressive 
stresses conveyed through the tie 10. On the other hand, if they are too 
hard, it becomes impossible for them to fully absorb vibration. Further, 
they should be in a liquid state when injected between the tie 10 and the 
roadbed 12, or else injection becomes difficult. Therefore, injection 
materials should be liquid when injected and after having hardened they 
should be strong, undergo minimum deformation against compressive stress 
and have a good vibration absorbance. 
We have numerically embodied the various requirements of a train rolling 
conditions and also have tested many injection materials and checked their 
properties. At the same time, we have carried out a vibration experiment 
using a track model consisting of a bed of ties 2 m wide .times. 0.5 m 
long, in which experiment an injection material was injected between the 
ties and the roadbed. After the injected material hardened, a 4-ton static 
load and a 4.5-ton vertical vibration load were simultaneously applied to 
the ties and a one-million vibrations test was conducted. As a result, we 
have found that it is possible to determine the properties required of the 
material and the amount of deformation of the injection material produced 
by the vibration experiment. 
Experiments were also made with respect to the working property of the 
materials and to their injection requirements. As a result, it has been 
found that the viscosity of the injection material at the time of 
injection is an all important factor to determine their mode of 
application. 
With respect to the injection property, it is preferable that the material 
to be injected between the tie and the roadbed be in the liquid state and 
that it form layers. This is advantageous not only for the working 
property of the material but also to alter the level of the tie as desired 
even if the roadbed surface is not perfectly regular. 
With respect to the injection temperature, it is desirable that the 
injection be conducted at a temperature below 200.degree. C. so as to 
prevent damage to the bed constituents because the injection material has 
to contact concrete products, crushed stones, etc. Further, when the 
efficiency of injection operation is taken into consideration, it is 
desirable to use injection materials with viscosities of 30 poise or lower 
at a temperature below 200.degree. C. However, as set forth hereinbefore, 
in addition to the injection property, other properties required at time 
of use are still more important. 
When consideration is given to the condition under which the injection 
material functions after it has hardened, it is necessary to consider the 
temperature condition for the dynamic properties of the material during 
operation and service. In particular, during the summer season, this 
temperature condition becomes important. In this connection, we have 
checked the temperature distribution in summer by using a track model. As 
a result, it became clear that the temperature under the tie may be 
assumed to be 40.degree. C. at the highest. That is, the deformation 
resistance of the injection material when in service must be checked at a 
temperature of 40.degree. C. and under this condition the material must 
display a satisfactory performance. 
There are various forces applied through the tie onto the injection 
material. However, the compressive stress and shearing stress are the two 
main forces. What is particularly critical in the injection material is 
its physical property against the compressive stress. The compressive 
stress applied through the tie onto the injection material is attributable 
mainly to the impact force caused by an irregular motion which occurs due 
to the static load and the rolling of the train. This impact force is an 
overall force dependent on variations in the condition of the train and of 
the track and on the speed of the train. Thus it is extremely difficult to 
calculate exactly such impact force. For the reasons mentioned above, it 
would be insufficient to consider only the elastic modulus for the 
property of the injection material, that is, the concept of loaded speed 
must also be taken into account. 
We have checked the properties of various materials, such as, thermoplastic 
materials and reaction-hardenable materials and we have also conducted the 
foregoing load vibration experiment thereon. As a result, it became clear 
that, since the physical property of the injection material is correlated 
to the amount of deformation of the material at the end of the load 
vibration experiment, the material preferably should have a compressive 
stress at 10% strain of 0.4-30 kg/cm.sup.2 at a compressive strain rate at 
40.degree. C. of 1.5% per minute. It also became clear as a result of the 
experiments that if the value of the compressive stress is above 0.4 
kg/cm.sup.2, the injection material when in service undergoes little 
deformation throughout the year. For example, if the tie width is 73.3 cm 
and the tie spacing is 10 m, the point below the center of the tie is 
loaded when the train passes, generally in the following manner, as 
experimentally demonstrated: When using 50 kg rails, though the train 
speed also affects, a compressive stress starts to be applied when the 
wheel weight is about 2.5 to 3.0 m before the load point in question, and 
when the wheels reach just above the load point in question the point 
undergoes the maximum compressive stress, which is then gradually 
decreased. 
When the injection material is a visco-elastic body, the conditions are 
complex and unlike the case with an elastic body. The resistance to 
deformation under a compressive force is influenced by its loaded speed, 
it being weak at low loading speeds. For safety sake, therefore, the 
condition of a low loading speed has been adopted here. That is, if the 
maximum deformation is 10% when the train rolls at the very low speed of 
about 25 m/hr, a strain speed of 1.5%/min is appropriate. 
On the other hand, from the standpoint of protection of the roadbed, 
excessive compressive stress values are not desirable because of vibration 
absorbance, it being desirable that the value of compressive stress be 
below 30 kg/cm.sup.2. 
Thermoplastic materials and reaction-hardenable materials may be used as 
the injection material according to the present invention only if they 
satisfy the foregoing properties. As the thermoplastic material may be 
mentioned, for example, petroleum, natural or synthetic waxes and 
bituminous substances such as asphalts, pitches and tars, thermoplastic 
resins such as polyethylene, polypropylene, polystyrene, polyvinyl 
acetate, thermoplastic polyester, acrylic resins, polyvinyl chloride, 
polyacrylonitrile, diene plastics, ethylene-vinyl acetate copolymer resin, 
petroleum resin, cumarone-indene resin, rosin, polybutene, 
ethylene-propylene copolymer resin, terpene resin, thermoplastic epoxy 
resin, thermoplastic urethane resin, thermoplastic rubber, and sulfur. 
On the other hand, a reaction-hardenable material means the combination of 
reactive materials such as epoxy, urethane, polybutadiene and unsaturated 
fatty acid systems with curing agents for hardening the said reactive 
materials. Also, cement compositions may be used if various rubbers or 
resins in emulsified state are added thereto. The above-mentioned 
materials may be used either alone or in combination. In addition, 
additives such as fibers, fillers, oils, and rubbers may be added. 
EXAMPLE 
16 tons of 10/20 blown asphalt and 4 tons of a low molecular weight 
polyethylene (with an average molecular weight of about 700) were 
completely melted and mixed together. The mixture had a viscosity below 5 
poise at 200.degree. C. and a compressive stress at 10% strain of 0.62 
kg/cm.sup.2 at a compressive strain rate at 40.degree. C. of 1.5%/min. 
This material was used as the injection material in the Kansai Main Line 
in March 1974, and the range of use covered a section of track 75 m. It 
was injected at 180.degree. C. to form an injected layer about 2 cm thick 
between concrete ties 73.3 cm wide arranged side by side at an interval of 
10 m and a ballast roadbed (with No. 6 crushed stones of 12 mm dia 
dispersed and rolled after rolling of the ballast roadbed), and then it 
was allowed to cool and harden. When a check was made in October 1975 
(two summer seasons had passed since), there was observed no deformation 
of the injected layers.