U.S. patent application number 14/584809 was filed with the patent office on 2015-04-30 for method for producing a track superstructure which underwent partial foaming.
The applicant listed for this patent is MSB-Management GmbH. Invention is credited to Tim Frenzel.
Application Number | 20150115049 14/584809 |
Document ID | / |
Family ID | 38006967 |
Filed Date | 2015-04-30 |
United States Patent
Application |
20150115049 |
Kind Code |
A1 |
Frenzel; Tim |
April 30, 2015 |
METHOD FOR PRODUCING A TRACK SUPERSTRUCTURE WHICH UNDERWENT PARTIAL
FOAMING
Abstract
The invention relates to a method for introducing a flowable and
foamable reaction mixture from the top into a ballast body having
sleepers embedded therein, in which method said mixture is
introduced into the ballast body laterally of the sleepers, notably
preferably depending on the height of the ballast body at the point
of application, and in a quantity that is all the larger the more
upwards in the ballast body the application point is situated,
wherein the mixture is adjusted in such a way that the foam
formation process will begin only when the front of the mixture
flowing downwards inside the ballast body has reached the bottom
side or the region in the vicinity thereof of the ballast body so
that the foam formation is carried out within the ballast body from
the bottom towards the top.
Inventors: |
Frenzel; Tim; (Brunkensen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
MSB-Management GmbH |
Freden |
|
DE |
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|
Family ID: |
38006967 |
Appl. No.: |
14/584809 |
Filed: |
December 29, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12278676 |
Nov 24, 2008 |
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PCT/EP2007/051341 |
Feb 12, 2007 |
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14584809 |
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Current U.S.
Class: |
238/2 |
Current CPC
Class: |
E01B 1/001 20130101;
E01B 1/008 20130101 |
Class at
Publication: |
238/2 |
International
Class: |
E01B 1/00 20060101
E01B001/00 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 10, 2006 |
DE |
102006006118.7 |
Claims
1. A method comprising: introducing a flowable and foamable
reaction mixture from the top into a ballast body having sleepers
embedded therein, wherein the mixture is introduced into the
ballast body at the top of the ballast body and laterally of the
sleepers, and wherein the mixture is adjusted in such a way that
the foam formation process begins only when the front of the
mixture flowing downwards inside the ballast body has reached the
bottom side or the region in the vicinity thereof of the ballast
body so that the foam formation is carried out within the ballast
body from the bottom towards the top.
2. The method of claim 1, wherein, prior to the introduction of the
mixture, the ballast is first removed between the sleepers and
outside the load transfer regions of the ballast body and, after
foam formation, is applied again onto the ballast body between the
sleepers for UV protection of the surface-near region of the
foam.
3. The method of claim 1, wherein the method is used for
conditioning a ballast bed, and wherein hot air is introduced from
above into the ballast body, which air will laterally emerge from
the ballast body, while the relative humidity of the emerging air
is detected and the process of heating the ballast body will be
terminated when the average humidity of the air is below a
presettable threshold value.
4. The method of claim 3, wherein the humidity of the air laterally
exiting from the ballast body is detected at a plurality of sites
and an average value is obtained from these individual air-humidity
values, and that the heating the ballast body is terminated when
the average humidity of the air is below a presettable threshold
value.
5. The method of claim 1, wherein the mixture is introduced,
depending on the height of the ballast body at the point of
application, in a quantity that is all the larger the more upwards
in the ballast body the application point is situated.
6. The method of claim 3, wherein the mixture is introduced,
depending on the height of the ballast body at the point of
application, in a quantity that is all the larger the more upwards
in the ballast body the application point is situated.
7. The method of claim 1, wherein the mixture comprises a selection
of suitable components and additives to cause the foam formation to
occur upon a lapse of a certain time after introduction of the
mixture into the ballast bed.
8. The method of claim 1, wherein the foam comprises at least one
of a polyurethane foam, a polyester foam, a polystyrene foam, or a
polyvinyl chloride foam.
9. The method of claim 1, wherein the foam is formed in a load
transfer zone that is described by an angle of about 60.degree.
beneath the sleepers.
10. The method of claim 9, wherein the foam is formed throughout
substantially all of the load transfer zone.
11. The method of claim 9, wherein the load transfer zone comprises
a first load transfer zone formed under a first sleeper, further
comprising: forming the foam in a second load transfer zone formed
under a second sleeper adjacent to the first sleeper; and providing
an inclination along an interface between the first load transfer
zone and the second load transfer zone to enhance drainage of
moisture from the ballast body.
12. The method of claim 1, further comprising bonding surfaces of
the ballast body between the sleepers with an
ultraviolet-radiation-resistant material.
13. The method of claim 1, wherein introducing the flowable and
foamable reaction mixture from the top into the ballast body having
sleepers embedded therein comprises pouring the flowable and
foamable reaction mixture onto the ballast body.
Description
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/278,676, filed Feb. 12, 2007, which is a
National Phase Application based on International Application
PCT/EP2007/051341, filed Feb. 12, 2007, which claims the benefit of
German Application 102006006118.7, filed Feb. 10, 2006. The entire
contents of each of U.S. patent application Ser. No. 12/278,676;
International Application PCT/EP2007/051341; and German Application
102006006118.7 are incorporated by reference herein.
[0002] The invention relates to the production of a partly foamed
railroad track bed structure by introducing a flowable and foamable
reaction mixture into parts of the ballast body of the railroad
track bed structure.
[0003] Among the traditional and most frequently used track systems
today are ballasted tracks, optionally equipped with wooden,
concrete or steel sleepers. This track structure has been optimized
continuously from the beginnings of railroad traffic by practical
use and theoretic recalculation.
[0004] To obtain an economically feasible track system, the
durability of the main components--rails, sleepers, ballast and the
subbase--have to be properly matched. Low life cycle costs will be
incurred if the subbase has a longer useful life than the ballast
bed and the ballast bed has to be renewed only when the sleepers
have reached the end of their useful life. During the last decades,
the strong increase in load by more trains, higher loads per axle
and velocities, as well as heavy rolling stock have had the result
that, for economic reasons, the track unit was reinforced first by
using more rigid rail profiles and concrete sleepers. In a second
phase, the subbase was improved where necessary by applying level
protection layers and drainages in the course of a renewal of the
track bed structure. Thus, the ballast bed factually became the
weakest main element of the railroad track. The improvement of the
ballast properties is an important measure for securing a
sufficient useful life of the ballast bed made of stub stones which
has a high pore volume in a clean state.
[0005] Presently, speeds up to more than 300 km/h are achieved
(e.g. TGV) and heavy loads are transported on these tracks. The
structure engineering has adapted to these structures and today has
reached a high level worldwide.
[0006] From a theoretical point of view, the structure of a
ballasted track is a complicated and complex task to realize. It is
complicated because the ballast mass that is not a rigid, firm
structure changes when dynamically influenced.
[0007] This means: When a track is laid, so-called tamping machines
are used to compact the ballast after the track unit has been laid
on a ballast bed of at least 30 cm in thickness. The track unit
then rests on the ballast bed and transfers the loads from the
passage of a train to the sleepers via the rails and from the
sleepers on to the ballast bed. Ideally, the loads are then
distributed in the ballast bed from stone to stone down the
subjacent level and are then transferred into the subbase.
[0008] Here, the purely static transfer of the loads introduced is
realized without any problems.
[0009] However, changes in the structure of the ballast bed will be
caused by the dynamic load occurring during a train's passage.
[0010] As it is known, when a train passes, positive and negative
loads are introduced. This means that perpendicular loads and,
additionally, relieving leading and hunting waves are applied to
the track. In combination with the dynamic frequency of the train's
running the "stone-on-stone structure" may thus change. The ballast
stones turn, becoming round in the end, and the position of the
track changes. If this were an entirely uniform process, no
disadvantage would result therefrom for the track system. However,
this is not the case due to the routing of the track--bends,
straight parts, bridges, different substrates, etc. In intervals,
the ballast has to be compacted again with tamping machines, so as
to preserve a good track position for a longer period.
[0011] Today, freight trains run with a load of 22.5 t per axle.
This load is transferred from the bottom of the sleepers to an
average of about 330 ballast stone tips, from where it is passed
downward from stone to stone. Thus, only 12% of the base area of
the sleeper are used as the footprint. These values hold for both
horizontal and vertical load transfer. The void volume in the
ballast body is about 40%, i.e. there is ample space to allow for a
turning or displacement of individual ballast stones upon dynamic
load.
[0012] In the past, different methods have been developed to
counteract this problem: [0013] 1. Track systems without ballast,
so-called "fixed railways", have been and are developed. These may
have a subbase of concrete or of asphalt. [0014] 2. After the track
has been finally compacted, the ballast body is cast with a
cement-like mixture, thus becoming rigid. [0015] 3. After the track
has been finally compacted, the ballast body is treated with a
liquid plastic material, whereby the stones are adhered pointwise
at the contact points between the stones.
[0016] A variety of past approaches are known that attempt to alter
the characteristics of technical structures, for example to enhance
stability by effective "cohesion" of the stones.
[0017] From DD 86 201 and DE 24 48 978 A1, for example, a full or
partial bonding of all ballast stones of the ballasts structure is
known. This causes draining problems, since surface water can no
longer penetrate the ballast body in the vertical or the horizontal
direction, which is particularly disadvantageous with railways
including two or more tracks and especially in bend areas. A full
bonding of all ballast stones is also known from DE 20 63 727,
using a bonding material, possibly adapted to be foamed. A machine
with which this full bonding can be achieved is described in U.S.
Pat. No. 3,942,448 and DE-U-7319950, respectively.
[0018] From DE-A-23 05 536, a method for lifting tracks is known,
wherein a swelling material is introduced into the track body
through the rails for the purpose of lifting the track body.
[0019] Finally, it is known from EP-A-1 619 305 to provide drain
mats under a ballast bed which has been foamed only in the load
transfer regions of the ballast body. The advantage of this
construction of the track bed structure becomes evident
particularly in railroad lines with two or more tracks. Surface
water (e.g. rain water) accumulating in the surface-near region of
the ballast body between the sleepers and above the partial
foaming, will enter the region between two tracks and, since this
region is free of foaming, will be able to flow off from there to
the subgrade, whereupon, from the subgrade, the water will flow off
via the drain mat of the adjacent track arranged below the ballast
body of the adjacent track and on the subgrade of this track.
[0020] It is an object of the invention to provide a method for
introducing a flowable and foamable reaction mixture from the top
into a ballast body having sleepers embedded therein, in which
method the foaming of the ballast body within the load transfer
regions of the sleepers, as shown e.g. in EP-A-1 619 305, shall be
reliably effected.
[0021] According to the invention, to achieve the above object,
there is proposed a method for introducing a flowable and foamable
reaction mixture from the top into a ballast body having sleepers
embedded therein, in which method said mixture is introduced into
the ballast body laterally of the sleepers, notably depending on
the height of the ballast body at the point of application, and
preferably in a quantity that is all the larger the more upwards in
the ballast body the application point is situated, wherein the
mixture is adjusted in such a way that the foam formation process
will begin only when the front of the mixture flowing downwards
inside the ballast body has reached the bottom side or the region
in the vicinity thereof of the ballast body so that the foam
formation is carried out within the ballast body from the bottom
towards the top.
[0022] Thus, in the invention, it is proposed to adjust the
flowable and foamable reaction mixture to the effect that the foam
formation process will occur only upon lapse of a certain time
after introduction of the mixture into the ballast bed. Such delays
of the foam formation process are possible by selection of suitable
components and additives for the flowable and foamable reaction
mixture. Thereby, according to the invention, a foam formation
process occurs within the ballast body from the bottom towards the
top, i.e. up to a location under the sleepers. Since the process of
introducing the flowable and foamable reaction mixture is performed
laterally of the sleepers, it can also be accomplished that the
foam formation process will occur only in parts of the ballast
body, notably within the load transfer regions, starting from the
sleepers and proceeding downwards at an angle of about
60.degree..
[0023] By way of alternative, it is also possible to first remove
the ballast between the sleepers and outside the load transfer
regions of the ballast body and then to introduce the flowable and
foamable reaction mixture while performing the above described
control of the time of foam formation process. Subsequently,
ballast will be introduced again into the previously cleared
regions, which will serve for UV protection of the surface-near
region of the foam.
[0024] Suitably, for conditioning the ballast bed, particularly in
preparation of the performance of the method of the invention, hot
air is introduced from above into the ballast body, which air will
laterally emerge from the ballast body, while the relative humidity
of the emerging air is detected and the process of heating the
ballast body will be terminated when the average humidity of the
air is below a presettable threshold value.
[0025] By the drainage of humidity from the ballast bed, improved
conditions are generated for the subsequent foam formation process.
The introduction of heat into the ballast body can be controlled in
dependence on the emerging humidity of the air in that, for this
purpose, the humidity of the air laterally exiting from the ballast
body is detected at a plurality of sites and an average value is
obtained from these individual air-humidity values, while the
heating the ballast body will be terminated when the average
humidity of the air is below a presettable threshold value.
[0026] By the inventive method for introducing a flowable and
foamable reaction mixture from the top into a ballast body having
sleepers embedded therein, there can be realized a method for
making a track bed structure for a railway on a subgrade inclined
transverse to the length thereof, wherein [0027] an elastic drain
mat can be arranged on the subgrade, [0028] a ballast body of
individual ballast stones having voids between them can be formed
on the drain mat, [0029] the track (sleepers with rails) can be
embedded in the ballast body, and [0030] according to the
invention, for positional fixation of the ballast stones arranged
substantially only within load transfer regions of the ballast body
below the sleepers, a foamable material is introduced into the
voids between the ballast stones.
[0031] It is advantageous for the chemical reaction during the foam
formation if the ballast body is heated or is at an elevated
temperature before introducing the foamable material, which,
depending on the ambient conditions, may be achieved even without
heating by an additional heat source.
[0032] Further, as already stated above, sleepers with a footing of
an elastic material, especially plastic material, are embedded in
the ballast body.
[0033] Suitably, the per se known steps of compacting and/or
causing a first settlement by vibrating the ballast body are
performed prior to the step of partly foaming the ballast body, in
which the same is filled with foam exclusively in the load transfer
regions.
[0034] The main problem of the known ballasted track--the turning
of the stones under dynamic load--is thus prevented, according to
the invention, in that, after the new or renewed track has been
finished, the track is foamed with a foam material in the ballast
body only in the load transfer regions.
[0035] This means that all voids between the ballast stones beneath
the sleeper and in the adjacent load transfer regions are closed by
the foam to be introduced into the ballast body; the voids between
the sleepers and outside the load transfer regions remain free,
thus serving to discharge surface water. The foam is adjusted such
that it will be flexible. The introduction of the foam and the
forming thereof in the ballast body does not alter the morphology
of the ballast body.
[0036] The foam of choice is a PU foam. PU foams have been known
for decades in industry and construction. Their adaptation to the
respective application poses no problems. Their use in humid
weather is not detrimental but rather beneficial.
[0037] All ballast stones of the track within the load transfer
regions are bonded by the introduced foam to form a unitary ballast
structure. The adhesion of the foam to the ballast stones and the
density of the structure of the foam can be adapted to the
magnitude of the maximum load introduced, with added safety
coefficient.
[0038] After the foam has cured, all forces introduced by a train
riding thereover can be transferred via this homogenous structure,
notably through the ballast stones and not through the foam which
serves to fix the ballast stones in a stable position.
[0039] Since the foam is composed of a plurality of pores, no rigid
ballast body is obtained by closing the voids. Rather, a structure
with an infinite number of "shock absorbers" is formed. Thereby, an
acoustic insulation is obtained in addition.
[0040] The present invention thus takes an alternative approach to
the stabilization of the ballast body without influencing its
morphology and with consideration to the problems of draining
[0041] This, with the invention, there can be provided a track bed
structure for a railway on a subgrade inclined transverse to the
length thereof, which track bed structure is provided with [0042] a
ballast body of individual ballast stones, and [0043] sleepers
embedded in the ballast body, on which rails may be mounted, the
ballast body comprising load transfer regions beneath the sleepers,
said regions being effective to receive loads acting vertically on
the ballast body via said sleepers when a train rides on the rails,
and to transfer these loads to the subgrade below the ballast
body.
[0044] In this track bed structure, substantially only the voids
between the ballast stones within the load transfer regions of the
ballast body are filled with a foam material, especially a PU foam
material, for fixing the same in a stable position, and, further,
an elastic drain layer can be arranged between the ballast body and
the subgrade.
[0045] The basic idea is to be seen in that the ballast body is
filled only partly with a foam material, however, within the
above-mentioned regions, the voids between the ballast stones are
substantially completely filled with this foam material, it being
guaranteed that the track system morphology remaining unaltered by
the foaming as compared to the state of the ballast body before the
introduction of the foam material. These regions of the ballast
body are the load transfer regions beneath the sleepers, these load
transfer regions extending obliquely sideward from the sleepers and
below the sleepers. By this partial foaming of the ballast body, as
provided by the invention, the voids between the ballast stones
within the zones of the ballast body between the load transfer
regions remain free so that surface water can flow away downward
or, within these zones, to the sides. Surface water reaching the
ballast body from the sides can also pass through the ballast body
in the horizontal direction.
[0046] Due to the partial foaming of the ballast body, it is just
those ballast stones that are most "loaded" during a train's
passing over the track that remain in a stable position. Thus, they
permanently maintain the position assumed after the compacting and
the (artificial) first settlement of the track bed structure, and
they do so substantially for the entire service life of the track
bed structure. A subsequent compacting, as it is required today for
track ballast bodies, can be omitted.
[0047] A foam useful with the present invention is a rigid foam or
a semi-rigid foam, i.e. a foam that mounts considerable resistance
against deformation. The foam must have a sufficient pressure
resistance. The foam may be adjusted with respect to pressure
resistance, reaction times, reaction components, and pot life.
Useful foam materials are, among others, polyurethane (PU),
polyester (PES), polystyrene (PS) or polyvinyl chloride (PVC)
foams. The foam may be closed-cell or open-cell foam. Open-cell
foams are advantageous in that they are acoustically effective,
which is favorable in track structure applications. The foam should
be elastic, of long-term stability, resistant to degradation,
fire-resistant, resistant to vermin and to chemicals.
[0048] To provide a possibility for draining below the track bed
structure, the ballast body is arranged on an elastic drainage
layer. Here, drain mats known for drainage purposes may be used,
such mats being supplied, for example, by Rehau AG. Porous rubber
mats or mats of another elastomeric material are advantageous.
Elastomer granulates are particularly useful, whose particles are
interconnected while leaving voids extending horizontally and
vertically through the mats. For example, particles of recycled
tires are suited for making such elastic drain mats. An elastic
elastomeric drain mat can receive high weights and contact forces,
is stable over extended periods and resistant to degradation, and
also has the other properties mentioned above that preferably apply
to the foam.
[0049] Up to the present, drain mats could not be used under
ballast bodies, since they cannot withstand the loads that occur
over time and are caused by several compacting operations.
According to the invention, however, only a single compacting
operation is required, namely when making the track bed structure.
In this respect, it is another merit of the invention to have been
successful in providing a draining material under the track bed
structure due to the elimination of subsequent compacting
operations. The drainage causes a controlled and directed discharge
of water that effectively prevents an erosion of the subgrade
(ground level). Further, as described above, the material of the
drain mat contributes to the long-term stability thereof, whereby
it maintains its (horizontal) porosity even under high pressure
loads.
[0050] For a further fixation of the ballast stones within the load
transfer regions, it is feasible to provide the bottom faces of the
sleepers with an elastic material, especially a plastic material
(so-called sleeper footing). Such sleepers with footings are found
in EP-A-1 298 252, for example. The ballast stones contacting the
sleeper penetrate into the elastic material of the sleeper footing,
whereby a fixation similar to a "catch connection" is obtained.
[0051] The PU foam introduced improves the track body in many ways:
[0052] The subgrade beneath the ballast is protected from frost by
the high insulating capacity of the air micro-voids in the PU foam.
[0053] The subgrade beneath the ballast is protected from water.
[0054] The risk of a distortion of the track in the horizontal or
vertical direction is reduced, since higher forces can be received.
[0055] The resistance of a track to transverse dislocation is
increased. [0056] The dynamic load on the subgrade and the vicinity
is reduced. [0057] The calculation methods regarding the positional
stability of a track can be optimized. [0058] The ballast body has
an acoustically insulating effect (reduced transfer of vibrations
from the track body both via the ground and the air, with the
drainage mat additionally serving for sound decoupling).
[0059] The requirements of the present method and the ballast body,
respectively, are as follows: [0060] 1. washed ballast stones
[0061] 2. tracks, compacted and approved under railroad engineering
aspects [0062] 3. track ballast cross section thermally
prepared--temperature parameter [0063] 4. curing times and
flexibility of the foam can be influenced [0064] 5. absolute full
foaming of the respective load transfer zones (angle of approx.)
60.degree. beneath the sleepers [0065] 6. recyclability according
to KrW/AsfG [0066] 7. compliance with requirements as to shear
resistance, tear resistance and spring stiffness of the foam
depending on the respective application.
[0067] The track system of the present invention is built as
follows: [0068] 1. After having finished the subgrade level and
prior to applying the track laying ballast, an elastic drain mat
(e.g. Securdran.RTM., available from Naue-Fasertechnik GmbH &
Co. KG) is placed on the surface of the PSS (level protection
layer) beneath the footprint of the ballast. It is thus guaranteed
that in lines with two or more tracks the drainage of the center is
permanently secured. In one-track lines, this can be omitted; a
drainage of the edge zone that is higher due to the inclination of
the level is obtained (this is also true for multi-track lines).
[0069] 2. The bottom faces of the concrete or steel sleepers to be
built in are preferably provided with a footing of plastic material
according to prior art (e.g. EP-A-1 298 252). Thus, upon
compacting, the ballast stones are wedged into the structure of the
plastic material and retained there. [0070] 3. The track built and
compacted using the tamping machine is treated additionally with a
track stabilizer of known construction. Thereby, first settlements
otherwise caused by the train load to be expected are anticipated.
The track bed structure is now in a state for approval under
railroad engineering regulations. [0071] 4. The track is foamed
beneath the sleepers and in the adjacent regions of pressure
dissipation in the ballast body. To this end, the ballast body is
advantageously thermally treated and cleaned (washed ballast
stones) beforehand.
[0072] The present invention is not based on the assumption that
loads from train operation are transferred or dissipated by the
foam. The built-in foam stabilizes the ballast body and prevents
the ballast core to become displaced from the ballast body made and
compacted with the tamping machine. The approved quality of the
veritably stable ballasted track is maintained as built for a long
time. In this respect, the durability of the foam (e.g. PU) and the
composition thereof are of great importance.
[0073] As a rule, the technical behavior of particle-supported
structures is not altered when foam (e.g. PU) is used. Only the
properties of technical strength and rigidity are substantially
enhanced. Moreover, PU foam also improves dynamic features
regarding properties such as the insulating level and the velocity
of the load pressure waves (e.g. compression wave, shear wave and
surface wave).
[0074] When using a foam (e.g. PU), it is desirable to make sure
that the reinforced and stabilized subbase functions on an
acceptable level during its useful life.
[0075] PU foam is preferably used in the proper spatial position
and to the proper depth to guarantee that the improvements in the
technical behavior are achieved. Moreover, PU foam is preferably
built up chemically to be sure that its desired properties are
appropriate for the respective application with consideration to
rigidity, strength, viscosity, fatigue limits, acoustic insulation,
temperature range, biochemical and hydroscopic properties, curing
time and service life. The market offers freely available foams
that can tolerate temperatures in a range from -30.degree. to
+80.degree. C., are resistant to vapor and water, do not shrink or
exert any dwell pressure, and are resistant to excrements (this
should not be neglected, since many passenger wagons still have
open toilet systems and thus discharge excrements onto the
ballast). To achieve the desired behavior and a predictability,
additional agents can be used in the PU foam to further extend the
chemical properties. There are plenty of ready-mixed foams with
corresponding properties that will be selected according to the
given circumstances.
[0076] The invention provides a stabilized ballast superstructure
in a railroad track made according to this method. Preferably, PU
foam can be used to increase the vertical and/or longitudinal
stability of the subbase (e.g. the rigidity and strength). The
system should be controlled carefully to guarantee that the
dynamic, vibratory or static loads and forces remain within the
fatigue or load limits of the superstructure reinforced with PU
foam, including a predefined safety factor and with consideration
to the desired life cycles. Adding a PU foam causes a positive
change in the static and dynamic behavior of the superstructure
made of particles, thus also changing the overall and partial
behavior of the subbase.
[0077] Types of ballast superstructures that are reinforced and
stabilized by the previously described treatment method may also be
used for: [0078] a rapid stabilization of overloaded subbases until
their final repair of the track section (e.g. removing slick and
"wet spots" in a railroad track), [0079] vertical, lateral and
longitudinal stabilization (in a track e.g. transition curves, high
banks, to reduce maintenance efforts, for example), [0080]
stabilization of tunnel tracks, [0081] reinforcement of bridge
tracks, including the transitions before and behind bridges to
prevent load surges, [0082] reducing the load on the track system
by increased PU foam rigidity and strength properties, [0083]
preventing induced plastic load on and attrition of the separation
of particles (e.g. by splintering) by almost completely preventing
the movement of the particles, [0084] reducing the occurrence of
soiled particles, [0085] according to the invention, PU foam
membrane can be employed (e.g. at contact sites between different
subbase materials) to prevent the intrusion of dirt into the top
ballast/railway ballast, [0086] supporting, in combination with the
drain mat to be provided, the prevention of flow erosion of the
surface and the subbases, [0087] allowing for an increase of
applied loads and of the speed of vibrating loads without any
significant increase in maintenance of the subbase, and reducing
the damages to the subbase caused by the loads applied, [0088]
reducing the generation and transmission of ambient noise, [0089]
if desired, allowing for a low cost high-power cleaning (e.g.
suction devices) of the reinforced superstructure to maintain
tidiness (garbage, excrements, leafs, twigs, cigarette butts, etc.)
by bonding the ballast surfaces between the sleepers with another
(UV resistant) material in a single operation, [0090] improving the
static and dynamic performance parameters of the superstructure and
the subbase.
[0091] The composition of the foam is selected on the basis of the
stiffness and strength properties required by the composite.
Specifically, the tensile strength and shear strength properties
are determined as a part of the construction process.
[0092] In areas with unfavorable geological formations, the foam
properties (e.g. rigidity) are designed such that it can be
guaranteed that an effective cushion-like foundation of stabilized
ballast is built over the weak area. If the rigidity is high
enough, a more uniform load distribution is achieved at the
interface with the track body.
[0093] For track switches with high maintenance expenditure, the
foam properties are selected such that the strong vertical forces
are distributed more effectively under the track switch, however,
at the same time retaining good damping properties of the
composite. A lifting of the sleeper by the introduction of the foam
is substantially excluded.
[0094] When new tracks are laid, bores 20 may be provided during
manufacture at different places in the sleepers 11 so that the
foaming material can be directly injected into the underlying
ballast, stabilizing the same completely.
[0095] To allow for a vertical/horizontal adjustability in newly
laid tracks, commercially available rail fasteners (known as being
mounted in "fixed tracks", for example) have to be provided and
mounted to be able to later regulate a possible settlement of the
subgrade.
[0096] As is obvious from the description and the enclosed
drawings, the track body comprises foamed ballast and non-foamed
ballast.
[0097] The foamed region is always located under the sleeper and in
the load transfer regions. This forms a cone-like foamed structure
in the area of the sleeper.
[0098] Due to the e.g. two-track routing in straight line sections
or in bends with the necessary track banks, the selected sparing
foaming of the ballast bed forms regions in which the incidental
precipitation can not be discharged in the usual manner as would be
the case with a completely open ballast bed.
[0099] The selected embodiment including the plastic drain mat
placed on the subgrade level addresses this problem.
[0100] In all instances, the precipitation will reach the plastic
drain mats in the problematic zones, from where it is discharged
outward in a controlled manner.
[0101] Due to the chosen placement over the entire surface under
the sleepers, water leaves no traces of erosion on the subgrade and
thus contributes to the protection of the subbase of the track.
[0102] Further, according to the invention, it is proposed to
prepare mineral fractions such as e.g. rock matter and particularly
track-ballast stones, gravel etc. connected to each other by a
preferably foamed polymer material such as e.g. a PU-based foam, in
that [0103] the polymer-fixed mineral fractions are introduced into
a furnace, preferably a rotary furnace, [0104] the polymer-fixed
mineral fractions are heated in such a manner that the polymer
material is converted into the gaseous phase, [0105] the gas is
subjected to an exhaust-gas cleanup process, and [0106] the mineral
fractions substantially freed of polymer are removed from the
furnace.
[0107] The invention will now be explained in detail with reference
to the drawings. In the Figures:
[0108] FIG. 1 is a vertical section through a track bed structure
according to the present invention, intended for a one-track line
section,
[0109] FIG. 2 is a top plan view on the track bed structure of FIG.
1,
[0110] FIG. 3 is a vertical longitudinal section through a track
bed structure according to the invention, intended for a one-track
line section, and
[0111] FIG. 4 is a vertical section through a track bed structure
according to the invention, intended for a two-track line
section.
[0112] FIGS. 1 to 3 illustrate a first embodiment of the present
track bed structure. The track bed structure is situated on a
subgrade or level ground 12 that is inclined as usual and may have
a protective layer of asphalt or gravel. A drain mat 14 lies on the
subgrade 12 (level), on which a ballast bed 16 of individual
ballast stones 18 (indicated in FIGS. 1 and 2 and shown in detail
in FIG. 3) is applied. Sleepers 20 (of wood, concrete or steel) are
embedded in the top portion of the ballast bed 16, to which the
rails 24 are mounted by means of especially vertically adjustable
fastening points (schematically indicated at 22).
[0113] Starting from the sleepers 20, the load transfer regions 26
are defined in the ballast bed 16, within which the loads
introduced during the passage of a train over the rails 24 are
transferred to the subgrade 12.
[0114] In the section of FIG. 3, these load transfer regions 26 are
of a trapezoidal shape. In the end portion of the ballast bed 16
facing the subgrade 12, the load transfer regions 26 merge. In top
plan view, the load transfer region 26 is as illustrated in FIG. 2.
The regions between adjacent load transfer regions 26 are
substantially V-shaped.
[0115] Prior to the start-up of the track bed structure 10, the
ballast bed 16 is compacted and vibrated to cause a first
settlement.
[0116] According to the invention, the voids between the ballast
stones 18 are now completely filled with foam within the load
transfer regions 26, preferably with a PU foam 28 adjusted
according to the requirements and loads. Regarding the pressure
resistance, adhesion and foaming behavior, PU foams may be adapted
to the respective requirements, as known per se, resulting in a
foam material optimized for the respective application. The ballast
stones 18 within the load transfer regions 26 are thus fixed in
position; the sleepers 20 have footings 30 of (elastic) plastic
material on their underside. The foam may also be provided
laterally of the lower portion of the sleepers 20 so that these are
embedded in ballast bed portions provided with foam 28.
[0117] As is obvious especially in FIG. 3, in the present track bed
structure 10, the regions 32 of the ballast bed 16 between the load
transfer regions 26 remain free of foam so that precipitation can
flow off transversely through the track bed structure 10. By
providing an inclination along the interface between two adjacent
load transfer regions 26, indicated at 34 in FIG. 3, which forms
the base of a zone 32, this drainage is further enhanced.
Precipitation falling on the ballast bed 16 on the sides of the
track outside the load transfer regions 26 (as indicated at 34 in
FIG. 1) or precipitation accumulated at the side of the ballast bed
16 will be discharged via the drain mat 14 below the track bed
structure 10.
[0118] The benefit of a drain mat 14 below the track bed structure
becomes particularly obvious with line of two or more tracks, as
illustrated in FIG. 4. As far as the individual elements of the
track bed structure 10' of FIG. 4 are identical or similar to the
elements of the track bed structure 10 of FIGS. 1 to 3, they bear
the same reference numerals in FIG. 4.
[0119] Precipitation accumulating within the zones 34 of the right
part of the ballast bed 16 in FIG. 4 flows off to the center 38 of
the ballast bed 16, from where it is drained via the left part of
the drain mat 14 in FIG. 4 under the left track in FIG. 4.
[0120] The following device, for example, is suitable for
introducing the foam into the ballast bed:
[0121] Railroad tracks are conventionally laid in ballast beds onto
sleepers of different materials. Since wooden sleepers can be
conserved only by use of problematic substances, use is made
largely of concrete or steel sleepers. The forces resulting from
the mass of the trains and from the dynamic effects of the
movements of the trains are transferred from the rail via the
sleeper into the ballast body. This load transfer takes place
substantially in a region at an angle of 60.degree.. In the viscous
ballast region, the introduced forces cause a movement of the
ballast stones which, similar to the effects acting on ballast
matter on riverbanks, leads to abrasion of the edges and thus to a
rounding of the ballast pieces.
[0122] To prevent these effects, the ballast body is fixed by use
of foam, preferably polyurethane, in the region of the load
transfer. The foam will enclose the ballast pieces in a
form-locking manner and enter a permanent connection with their
surface. The foam is adjusted to have flexible properties and will
not alter the morphology of the ballast bed. Thus, the static
structure of the ballast will remain fully intact. In the upper
region of this foamed ballast body, the concrete or steel sleeper
or switch construction weighing on the ballast body will be
permanently bonded to foam. Thereby, the effect of the transfer of
horizontal forces into the ballast bed, which in wooden sleepers is
obtained by the clawing of the ballast stones into the underside of
the sleepers, is considerably improved and rendered permanent.
[0123] As a further effect, apart from the fixing, there is
obtained a considerable reduction of the vibrations from the track
body via the ground as well as via the air.
[0124] For the drainage of precipitation water which may accumulate
between the tracks and the formed foam cones, a drainage mat of
structured recycled rubber is a inserted under the ballast body.
The mat is configured to drain the precipitation water horizontally
under the ballast body. The mat is on both of its sides surrounded
by a nonwoven, preferably a geotextile, thus effecting a long-term
prevention of clogging of the pore volume. To facilitate the
mounting process, the longitudinal edges of the geotextile are
formed with alternately projecting portions so that the abutting
edge to the respective next mat is covered, i.e. that the nonwoven
on its top side projects in the region of one or two edges of the
mat and that the nonwoven on its bottom side projects in the region
of one or two edges of the mat opposite the above edges.
[0125] For introducing the foam into the ballast bed, there is
preferably used the following device:
[0126] The foam is introduced into an existing track bed which has
been washed by a cleaning machine and provided with a drainage
path, or into a track bed newly built according to specifications
(washed ballast, drainage path) using a device mounted on a railway
vehicle. This device comprises the following sections: [0127] a
traction vehicle [0128] a supply store for each respective tank
holding the components of the foam [0129] a supply store for fuel
used to heat and dry the track body [0130] a heating and drying
unit, pressurized air supply store [0131] a foam applicator [0132]
measuring and control unit with documentation.
[0133] The traction vehicle may be a vehicle allowing for a step
operation and a displacement of <1 m/sec, whereby the unit can
be positioned with an accuracy in the centimeter range.
[0134] The supplies stores are equipped with KTCs that may be
filled in the plant and may be positioned on and taken off the unit
by use of a crane.
[0135] The heating and drying unit comprises one or a plurality of
bells, which may be lowered and into which hot air from a support
burner is supplied by blowers via air conduits. The bells are
provided with a sealing bead toward the ballast body and toward the
track regions so that, as far as possible, no hot air can escape
upward from the ballast bed but only, as far as possible,
laterally. Three of these units are arranged in series to set the
necessary parameters of the foaming depending on the outside
temperature and the humidity of the ballast. With the aid of
built-in elements which are adapted to be folded out and which are
fastened inside on the heat aggregates, it is also possible to
conduct the heat separately to the tracks so as to heat the tracks
to a specific operating temperature or to cool them. In the latter
case, cooling aggregates, working via an airpath arrangement, will
be activated to blow a cool airflow around the rails for cooling
them. The heating may be effected using petrol products, gas or
natural vegetable oils. The exhaust gas heat and the waste heat of
the traction vehicle could also be used. The warm air saturated
with humidity will exit, laterally of the sleeper region, from the
track or ballast body, respectively. The condensation generated
herein in the lateral region will cause no disturbances because it
does not occur in the region of the load transmission which is the
target of the foam fixation. By measuring the humidity of the
exiting air, the effectiveness of the treatment of the ballast is
checked and controlled.
[0136] The foam is introduced into the heated and dried ballast. To
this end, a device is used, for example, that has up to eight
application nozzles per sleeper side and can serve a plurality of
sleepers, e.g. ten, at the same time. The foam lances may be
lowered individually into the ballast bed by means of a driving
means. The necessary amount of lowering is calculated for each
nozzle by a process computer by determination of the inclination of
the track body. Within the device, the nozzles may be displaced by
lateral drives and are positioned immediately beside the sleeper
body with the aid of measuring means. After the lances have been
lowered to the calculated point, the foaming process controlled by
the process computer is initiated and documented. In this process,
by a corresponding pumping activity for each nozzle, the calculated
amounts of components are pumped into the mixing head at the top
end of the nozzle, where they are mixed and are subsequently
pressed into the ballast body. The computer detects the end of the
foaming process and turns the pumps off or closes the valves at the
mixing head. The lance is at once blown free by use of pressurized
air.
[0137] After this cycle, the device is raised together with the
heating bells. During the phase of displacement of the device, the
heating of the air and the blowers are switched off. The machine
unit may then be displaced to repeat the procedure at the next
segment.
[0138] The nozzles are removably mounted to a part that receives
the drive, acting as a support for the vertical insertion into the
ballast body. The mixing head is mounted thereon. The lower part of
the nozzle is beveled so that the nozzle cannot rest in abutment on
a ballast stone and thus cause a closure of the lower orifice. The
tip of the nozzle will either effect a displacement of an
unfavorably situated stone or create sufficient free space for
guaranteeing an unobstructed discharge of the foam components.
[0139] The adjustment of the foam with regard to the starting time
for the foam-formation reaction and the reaction time is performed
in such a manner that a conical foam structure is formed in the
ballast bed and the ballast body is thus fixed in the
load-transmission cone from the bottom to the lower edge of the
sleeper.
[0140] The need for lancets can be obviated in that discharge
nozzles for the foamable, reactive, flowable mixture are provided
or positioned above the ballast bed. The nozzles are either
stationary or displaceable transversely across the track body. The
reactive mixture is adjusted in such a manner that the foam
formation process will start when the flowable mixture has reached
the lowermost region of the ballast body. Thus, the foam formation
process is performed in a an ascending manner, as it were, from the
bottom towards the top. Depending on the height of the ballast bed
at the position of the nozzle, the rate at which the mixture is
applied onto the ballast bed is changed. (The higher the ballast
bed is, the larger the discharged quantity per time unit will be.)
Thus, the respective quantity of the mixture that is required due
to the height of the ballast bed will be applied across the whole
width of the ballast bed below the track bed. The introduction of
the mixture is performed on both sides of each sleeper (i.e. when
viewed in the direction of the tracks, in front of and behind the
sleeper directly to the side thereof), preferably simultaneously.
Thus mixture, due to its viscosity, will from both sides of the
sleeper also proceed in the region under the sleeper by conically
spreading downward within the ballast body. Then, consequently, by
the foam-formation process starting from below, reactive mixture
will proceed from below up the region underneath the sleeper,
because the advancing foam front will press still non-reacting
quantities of the mixture from below towards the sleepers.
[0141] The nozzles for the introduction of foam are mounted to the
machine rack at a site corresponding to the insertion position.
Using hydraulic or electric step actuators, this rack can be
displaced both in a rectangular direction, i.e. transversely to the
track, and upwards and downwards. In this manner, it is guaranteed
that all computed insertion positions for the reactive mixture can
be serviced according to the prescribed process.
[0142] A precondition for the above described system for a ballast
bed to be arranged below tracks, switches and junctions resides in
a track body including ballast, sleepers and tracks, which has been
produced in the usual manner and has been approved of, with the
following exceptions: [0143] Use should be made exclusively of
washed ballast without dust portions [0144] Between the ballast and
the subbase, a drainage mat is to be inserted. The mats should
preferably be laid without defective sites so that the drainage of
wastewater from the intermediate space can occur fully
laterally.
[0145] After approval of the track body, the ballast between the
sleepers and outside the load transfer regions is removed (and e.g.
deposited to the side). After foam formation, subsequent to a
waiting period of e.g. 24 h, the ballast will be repositioned.
[0146] The introduction of the foam is performed by a system
performing the following operational steps: [0147] Providing
optimized conditions for foam formation by drying and heating the
installed ballast, the duty cycle of the heating being controlled
in dependence on the ballast height, i.e. the ballast volume. The
conditioning is performed by blowing hot air into the ballast.
[0148] Introducing the foamable flowable reaction mixture,
controlled in dependence on the height of the ballast that is
computed by the process computer on the basis of the measured track
inclination, so that the load transfer cone below the sleeps will
be foamed and thus fixed. [0149] The dosed quantities are computed,
controlled, logged, and documented for each application point so
that, with the framework of automatic quality assurance, defective
sites can be immediately detected and thus be excluded or touched
up. [0150] The foam is produced by automatic dosing and mixing
plants, thus allowing to safeguard a constant quality. In the lines
from the tank to the mixer, the components are thermostatted.
[0151] Environmental Acceptability
[0152] The above introduction method has no consequences of
relevance for the environment. The components for the foam are
transported in tested and approved containers (GGVS/GGVE/IMO);
storage at the construction sites will not take place; and
transportation is performed according to the just-in-time
principle.
[0153] The processing system is controlled in such a manner that
both components can only be conveyed at the same time and can be
discharged from the system in a mixed condition. Thus, there can be
discharged only foam which is not classified as a hazardous
material and cannot have toxic effects. The polymerization reaction
will be concluded already after about 20 seconds. During this
period, the system is not accessible.
[0154] The foam contains only a very small part of catalysts which
are ranked among the amines and can be washed off with rainwater.
These are substances which are biologically degradable in a very
easy manner and have an extremely short biological half-life. The
results of the elution tests are attached hereto per enclosure. The
tests revealed a significant decline of the eluate value in the TOC
already after a brief exposure period, which coincides with the
expectations. Subsequent to polymerization, which occurs already
after about 20 seconds, the rest of the substances of the foam are
fully water-insoluble. A dissolution of parts of the foam, also in
other solvents, will not be possible so that, after the elution of
the catalyst amines has faded, there is reached an absolute
environmental compatibility under observation of the mounting
specifications.
[0155] In case of fire, it may be assumed that polyurethanes are
self-extinguishing, which to the same extent holds true also for
the rubber sheet used as a drainage mat which as a building
material can be classified among B2. The gases generated during the
burning process and the substances which may be discharged as part
of the fire-fighting water can largely be considered as non-toxic.
Of course, one might imagine scenarios wherein, caused by
incomplete burning in case of under-stoichiometric supply of
oxygen, toxic gases such as e.g. carbon monoxide could be generated
in large quantities. This, however, would have to be attributed not
to the substances used but to a topographic situation which already
in itself could lead to negative consequences up to lethal
effects.
[0156] In railroad routes leading through tunnels, to reduce the
potentially inflammable material in any case, the products are
enriched by a highly nitrogenous substance, rendering them
practically non-inflammable. As to further tests, reference is made
to the attached literature.
[0157] Dismantling--Recycling
[0158] In case of dismantling of a railway line, irrespective of
the reason of the dismantling, the foamed body can be removed and,
by application of a method specially designed for the purpose, be
processed into clean ballast. In the process, the thermal
decomposition of the polyurethane occurs at temperatures
<550.degree. C. so that the ballast stones will remain
unaffected in their morphology, i.e. can be reused without any
further treatment.
[0159] The drainage sheets will be taken up and supplied to a
material recycling process. This will lead to an identical product
again.
* * * * *