DK2733263T3

DK2733263T3 - PROCEDURE FOR SECURING A DEEP BUILDING SITE

Info

Publication number: DK2733263T3
Application number: DK12192983.0T
Authority: DK
Inventors: Dr Torsten Erwe; Thomas Gross; Thomas Kleiner
Original assignee: Covestro Deutschland Ag
Priority date: 2012-11-16
Filing date: 2012-11-16
Publication date: 2018-06-14
Also published as: EP2733263B1; EP2733263A1

Description

The invention relates to a method and a protective wall for securing a civil engineering site, by means of which sandbagging or supporting of a base formation surrounding the civil engineering site can be avoided.

In civil engineering, a depression is introduced into subsoil. In order for a region of a base formation surrounding the civil engineering site not to fall under the action of gravity into the depression to be produced, it is in principle necessary to adhere to a particular angle of the bank at the margin of the depression to be produced. In this way, it is possible to provide a region around an imaginary boundary line delimiting the depression of the civil engineering site, in which region the required banking angle from the desired depth of the depression to the surface of the base formation can be provided. When there is not sufficient space for this region, for example due to other building works, driving a massive dividing wall into the base formation in order thereby to secure the civil engineering site even without formation of a banking angle sufficiently is known .

Driving a lance which releases a two-component mixture at a desired depth into a base formation surrounding a civil engineering site is known from EP 0 131 678 Al, DE 3 33 2256 A1 and DE 39 21 938 Al. The two-component mixture reacts to form a foam which strengthens the surrounding base formation. This is carried out at a number of different places which are at a distance from one another until the base formation surrounding the civil engineering site has been strengthened. A disadvantage here is that the stability of the strengthened base formation is not satisfactory. In particular, such methods of carrying out civil engineering work cannot be employed in the case of a porous but particularly hard base formation, in particular a ballast bed of a railway track system.

It is an object of the invention to indicate measures which make stable securing of a civil engineering site possible. In particular, it is an object of the invention to indicate measures which make stable securing of a civil engineering site possible in the case of a porous and hard base formation, in particular a ballast bed of a railway track system.

According to the invention, the object is achieved by a method for securing a civil engineering site having the features of Claim 1 and also a protective wall having the features of Claim 10. Preferred embodiments of the invention are specified in the dependent claims, which can individually or in combination represent an aspect of the invention.

The invention provides a method for securing a civil engineering site, comprising the steps of continuously applying a reactant mixture along a boundary line delimiting the civil engineering site to a surface of a base formation, in particular a ballast bed, allowing the reactant mixture to seep into the base formation and foaming the reactant mixture to form a solidified foam, wherein the foam and a part of the base formation surrounded by the foam form a protective wall extending along the boundary line and intended to hold back a base formation provided at an outer side face of the protective wall in the case of a base formation being removed at an inner side face of the protective wall.

Here, it is taken into account that a base formation which consists of naturally formed soils represents a porous crumbling mixture which comprises mineral constituents having a particular particle size distribution. This makes it possible for an in particular network reactant mixture having a sufficiently low viscosity to be able to penetrate without further assistants into intermediate spaces of the base formation and being able to flow in to a sufficient depth before the reactant mixture reacts to form a foam which strengthens the surrounding base formation with the aid of the foam formed so as to produce a protective wall. The base formation is particularly preferably a ballast bed, in particular a ballast bed of a railway track system, which has comparatively large intermediate spaces between the individual ballast stones, so that the reactant mixture can seep comparatively quickly to a sufficient depth into the ballast bed. Here, it is not necessary to drive a lance or a comparable aid in order to apply the reactant mixture to a particular depth in the base formation. As a result, even civil engineering sites in regions having a porous but hard base formation can be secured simply and in a space-saving manner.

As a result of the continuous application of the reactant mixture, bonding of the protective wall which essentially goes all the way through can be achieved. For example, the reactant mixture is applied continuously to the position of the boundary line, so that part of the reactant mixture which has already seeped in begins to foam while further reactant mixture is still being introduced. The part of the reactant mixture which has been applied later then begins to react to form a foam while the previously applied part of the reactant mixture is still foaming, as a result of which an essentially homogeneous foam is obtained. In particular, the previously applied part of the reactant mixture foams at a greater depth in the base formation than the part of the reactant mixture which has been applied later, so that the subsequent part of the reactant mixture can be pushed upward against the direction of gravity by the foam already being formed. This makes it possible for the protective wall to start to be formed at a defined depth in the base formation and to grow upwards essentially homogeneously from this depth. As a result of the homogeneous composite of the protective wall made up of cured foam and the part of the base formation surrounded by the foam in the vertical direction and/or along the boundary line, unnecessary phase boundaries and/or weak points can be avoided, so that the protective wall has increased stability and stable securing of the civil engineering site is made possible even in the case of a porous and hard base formation, in particular in the case of a ballast bed of a railway track system.

The application of the reactant mixture to the surface of the base formation can, in particular, be carried out by pouring, dribbling on and/or spraying. The application of the reactant mixture enables, in particular, the surface of the base formation to be wetted over its area, with the area wetted by the reactant mixture preferably being selected as a function of the desired thickness of the protective wall perpendicular to the boundary line. Here, account is likewise preferably taken of the expected depth of the protective wall in the base formation and/or the extent to which the protective wall is to have an essentially trapezoidal cross-sectional area. In particular, it is possible to make the protective wall thicker in the more highly loaded lower region and thinner in the upper region which is subjected to a lesser load. This makes a higher stability compared to a protective wall having a rectangular cross section possible for the same usage of material. The volume flow of the reactant mixture applied can particularly preferably be varied, in particular in order to be able to produce a protective wall having an essentially trapezoidal cross-sectional area. The reactant mixture is preferably applied at the same time at a plurality of places distributable along the boundary line, as a result of which a particularly homogeneous composite of the protective wall is obtained and the protective wall can be produced correspondingly quickly along the boundary line .

The "continuous" application of the reactant mixture can in principle be carried out continuously in the sense that a uniform, in particular homogeneous, composite of the solidified foam in the vertical direction and/or in the direction of the boundary line is produced. The expression "continuous application of the reactant mixture" can therefore also encompass methods of application which are actually carried out semicontinuously, for example in a pulsed manner, but have such short cycle times that the successively applied reactant mixtures give a foam composite without visually discernible boundary layers. In a preferred embodiment, the "continuous application of the reactant mixture" is carried out by application of the reactant mixture through an opening which is not closed during application, preferably with the aid of a pressure which is constant during application. The volume flow of the reactant mixture to be applied is particularly preferably always greater than zero and more preferably essentially constant.

The shaping of the protective wall, in particular the cross-sectional area and/or the thickness of the protective wall, is, in particular, selected in such a way that the protective wall withstands, preferably with addition of a suitable safety facing, the gravity-induced forces applied by the base formation surrounding the civil engineering site onto the outer side wall of the protective wall. Here, counterforces which may be applied by sides of the civil engineering site onto the inner side face of the protective wall are, in particular, not taken into account. The amount of reactant mixture which has seeped into the base formation is preferably such that, within the civil engineering site, the base formation can be removed completely on the inner side face of the protective wall, i.e. the side face facing the depression to be produced in the civil engineering site.

The boundary line is an imaginary line which separates the civil engineering site with the depression still to be produced later from the remaining base formation. The boundary line corresponds, in particular, to a region up to which the base formation is to be removed within the civil engineering site in order to produce the depression. For example, it is envisaged that a pit be excavated for the civil engineering site, so that the boundary line can be configured as a closed ring delimiting the pit. However, it is also possible for the civil engineering site to relate to one-sided removal of a raised base formation, so that a base formation projecting over the future depression is not present at all in a subregion of the periphery of the civil engineering site. In this case, the boundary line can be a line which does not cross over itself and is, for example, configured with an arc shape. Furthermore, it is possible for the protective wall to be produced only in a subregion of the boundary line, with a suitable banking angle being able to be provided in other regions of the boundary line.

As reactant mixture, it is possible to use, in particular, a polymer or a polymer reactive mixture which is preferably an epoxide or very particularly preferably a polyurethane reactive mixture. The cured foam is preferably polyurethane foam.

The polyurethane reactive mixture which is preferably used as reactant mixture preferably contains a mixture of a) one or more isocyanate compounds from the group consisting of polyisocyanates having an NCO content of from 28 to 50% by weight and NCO prepolymers having an NCO content of from 10 to 48% by weight derived from polyisocyanates having an NCO content of from 28 to 50% by weight and polyether polyols having a hydroxyl number of from 6 to 112, polyoxyalkylene diols having a hydroxyl number of from 113 to 1100 or alkylene diols having a hydroxyl number of from 645 to 1850 or mixture thereof and b) a polyol component consisting of one or more polyether polyols having a hydroxyl number of from 6 to 112 and a functionality of from 1.8 to 8 in the presence of c) from 0 to 26% by weight, based on the reaction components b) to g), of one or more chain extenders having a hydroxyl or amine number of from 245 to 1850 and a functionality of from 1.8 to 8, d) from 0.05 to 5% by weight, based on the reaction components b) to g), of one or more blowing agents, e) from 0 to 5% by weight, based on the reaction components b) to g) , of one or more catalysts, f) from 0 to 50% by weight, based on the reaction components b) to g), of one or more fillers and g) from 0 to 25% by weight, based on the reaction components b) to g) , of one or more auxiliaries and/or additives, with the index of the reaction mixture being in the range from 70 to 130.

In particular, the percentages by weight of the individual reaction components are selected with the proviso that the sum of the percentages by weight of the individual reaction components is less than or equal to 100% by weight.

For the purposes of the present invention, the index is the ratio of equivalents of NCO groups to OH groups and NH groups multiplied by 100. Thus, for example, an index of 110 means that there are 1.1 reactive NCO groups from the isocyanate compounds per reactive OH group or NH group or 0.91 reactive OH groups or NH groups per reactive NCO group of the isocyanate compounds.

The components for producing the polyurethane foams are used in a mixing ratio which allows homogeneous mixing of the components, in particular when using high-pressure machines. The use of high-pressure machines allows even fast-reacting PUR systems to be processed and an economical procedure thus to be realized. In addition, the use of the raw materials described in more detail below enables the processing properties of the PUR system to be set optimally according to the requirements. Thus, partial foaming of the base formation, in particular a ballast bed of a railway track system, can be realized using the pouring technique as application method. Furthermore, the mechanical properties of the polyurethane foams used can be varied within wide limits. The advantages of the PUR foams used are good compressive forces (at 10% deformation) (> 10.0 N) , good compressive strengths (at 10% deformation) (> 1.0 kPa) and tensile strengths (> 0.1 MPa) with low permanent deformation (compression set (40%, 25°C, 5 minutes) < 0.01%).

The polyurethane foams are preferably produced in the presence of chain extenders and catalysts. Preference is given to using catalysts which have primary and/or secondary hydroxyl and/or amino groups. The polyurethanes obtained in this way have improved emission behaviour and are distinguished, after extraction with solvents (for example water), by a reduced proportion of mobilizable constituents. The polyurethane foams according to the invention can optionally additionally contain fillers and also auxiliaries and additives known per se from polyurethane chemistry.

The reaction mixture for producing the polyurethane foam is adjusted with a view to the processing properties so that it can be applied using a simple application technique (for example casting methods). For example, partial filling of the base formation, in particular the ballast bed, with foam can be carried out by targeted setting of the reactivity of the reaction mixture. Such partial filling with foam firstly allows selective strengthening of the base formation along the boundary line of the civil engineering site and secondly makes the unimpeded outflow of liquids, for example water, possible. A reaction which is too slow would lead to the reaction mixture flowing into the soil or into lateral regions of the ballast bed. A reaction which is too rapid would lead to the reaction mixture not penetrating to the desired depth into the base formation. For example, in the case of a railway tack system having a ballast bed having a ballast height of about 40 cm, the cream time of the reaction mixture should be from 1 to 15 seconds, preferably from 1 to 5 seconds, and the setting time (fibre time) should be from 15 to 45 seconds, preferably from 15 to 30 seconds, with longer setting times being possible. Particular preference is given to selecting from 2 to 60 seconds, in particular from 4 to 40 seconds and more preferably from 5 to 30 seconds, as cream time of the reaction mixture, so that an appropriately great depth is obtained for the protective wall. The setting time can, in particular, be selected so that the foam being formed grows from a desired depth which is influenced by the cream time up to the surface or just before the surface or someone above the surface so that the protective wall can essentially provide a protective function over the total height up to the surface of the base formation and it is not possible for a part of the base formation which has not been removed to fall into a part of the base formation which has been removed.

The polyurethane foam used should preferably have a compression force (at 10% deformation) of at least 10.0 N, a compressive strength (at 10% deformation) of at least 1.0 kPa and a tensile strength of at least 0.1 MPa. Furthermore, it should preferably have a compression set (40%, 25°C, 5 min) of not more than 0.01% and good weathering or hydrolysis stability. The polyurethane foam used should also have a very small proportion of emittable or mobilizable constituents.

The polyisocyanates a) used are (cyclo)aliphatic or aromatic polyisocyanates. Preference is given to tolylene diisocyanate, diisocyanates and/or polyisocyanates of the diphenylmethane series which have an NCO content of from 28 to 50% by weight. These include mixtures of 4,4'-diisocyanatodiphenylmethane with 2,4'-diisocyanatodiphenylmethane and to a small extent optionally 2,2'-diisocyanatodiphenylemethane which are liquid at room temperature and optionally have been appropriately modified. Polyisocyanate mixtures of the diphenylmethane series which are liquid at room temperature and contain not only the isomers mentioned but also their higher homologs and are obtainable in a manner known per se by phosgenation of aniline-formaldehyde condensates are also well suited. Modification products of these diisocyanates and polyisocyanates which have urethane or carbodiimide groups and/or allophanate or biuret groups are also suitable. NCO prepolymers having an NCO content of from 10 to 48% by weight are likewise suitable as component a) . They are prepared from the abovementioned polyisocyanates and polyether polyols having a hydroxyl number of from 6 to 112, polyoxyalkylene diols having a hydroxyl number of from 113 to 1100 or alkylene diols having a hydroxyl number of from 645 to 1850 or mixtures thereof.

The components b) are polyhydroxypolyethers which can be prepared in a manner known per se by polyaddition of alkylene oxides onto polyfunctional starter compounds in the presence of catalysts. The polyhydroxypolyethers are preferably prepared from a starter compound having an average of from 2 to 8 active hydrogen atoms and one or more alkylene oxides. Preferred starter compounds are molecules having from 2 to 8 hydroxyl groups per molecule, e.g. water, ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, glycerol, trimethylolpropane, pentaerythritol, sorbitol and sucrose. The starter compounds can be used either alone or in admixture. The polyols b) are prepared from one or more alkylene oxides. Alkylene oxides which are preferably used are oxirane, methyloxirane and ethyloxirane. These can be used either alone or in admixture. When they are used in admixture, it is possible to react the alkylene oxides randomly and/or in blocks. Relatively high molecular weight polyhydroxypolyethers in which high molecular weight polyadducts or polycondensates or polymers are present in finely dissolved or grafted form are likewise suitable. Such modified polyhydroxyl compounds are, for example, obtained when polyaddition reactions (e.g. reactions between polyisocyanates and amino-functional compounds) or polycondensation reactions (e.g. between formaldehyde and phenols and/or amines) are allowed to proceed in situ in the hydroxyl-containing compounds b) (as described, for example, in DE 1 168 075) . Polyhydroxyl compounds modified by vinyl polymers, as are obtained, for example, by polymerization of styrene and acrylonitrile in the presence of polyethers (e.g. as described in US 3 383 351) , are also suitable as polyol component b) for the method of the invention. Representatives of the abovementioned component b) are, for example, described in Kunststoff-Handbuch, volume VII "Polyurethane", 3rd edition, Carl Hanser Verlag, Munich/Vienna, 1993, pages 57-67 and pages 88-90.

Preference is given to using one or more polyhydroxypolyethers which have a hydroxyl number of from 6 to 112, preferably from 21 to 56, and a functionality of from 1.8 to 8, preferably from 1.8 to 6, as polyol component b).

Suitable chain extenders c) are those which have an average hydroxyl or amine number of from 245 to 1850 and a functionality of from 1.8 to 8, preferably from 1.8 to 3. Examples which may be mentioned here are ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, triethanolamine, glycerol, trimethylolpropane and short-chain alkoxylation products. The component c) is preferably used in amounts of from 0 to 26% by weight, based on the reaction components b) to g) . Ethylene glycol, 1.4- butanediol, the propoxylation product of trimethylolpropane (OHN: 550) and mixtures of triethanolamine and diisopropanolamine (OHN: 1160) are particularly preferably used.

As blowing agents d), it is possible to use either physical blowing agents or water. Preferred physical blowing agents d) are 1,1-difluoroethane (HFC-152a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,1,2,3,3,3-heptafluoropropane (HFC-227ca), 1,1,1,3,3-pentafluoropropane (HFC-245fa), 1,1,1,3,3-pentafluorobutane (HFC-365mfc), n-pentane, i-pentane, i-hexane or mixtures thereof. Particular preference is given to using water as component d) . The blowing agents can be used either alone or in combination and are present in amounts of from 0.05 to 5% by weight, particularly preferably in amounts of from 0.3 to 3.5% by weight, based on the reaction components b) to g).

The intrinsically slow reaction between isocyanate and hydroxyl groups can be accelerated by addition of one or more catalysts c). Possibilities here are, in particular, tertiary amines of the type known per se, e.g. triethylamine, tributylamine, N-methylmorpholine, N-ethylmorpholine, N-cocomorpholine, N,N,N',N'-tetramethylethylenediamine, 1.4- diazabicyclo[2.2.2]octane, N-methyl-N'-di-methylaminoethylpiperazine, N, N-dimethylcyclohexylamine, N,N,N',N'-tetramethyl-1,3-butanediamine, N,N-di-methylimidazole-p-phenylethylamine, 1,2-dimethylimidazole, bis(2-dimethylaminoethyl) ether or 2-methylimidazole. It is also possible to use organic metal catalysts such as organic bismuth catalysts, e.g. bismuth(III) neodecanoate, or organic tin catalysts, e.g. tin(II) salts of carboxylic acids, for example tin(II) acetate, tin(II) octoate, tin(II) ethylhexanoate and tin(II) laurate, and the dialkyltin salts of carboxylic acids, e.g. dibutyltin diacetate, dibutyltin dilaurate, dibutyltin maleate or dioctyltin diacetate, either alone or in combination with the tertiary amines. Preference is given to using catalysts which have primary and/or secondary hydroxyl and/or amino groups. Possibilities here are both incorporatable amines and incorporatable organic metal catalysts of the type known per se, e.g. N-(3-dimethylaminopropyl)-N,N-diisopropanolamine, Ν,Ν,Ν'-trimethyl-N'-hydroxyethylbisaminoethyl ether, tetramethyldipropylenetriamine, 3-(dimethylamino)propylurea, tin ricinoleate. The catalysts can be used either alone or in combination. Preference is given to using from 0 to 5.0% by weight, particularly preferably from 0.5 to 5.0% by weight, of catalyst or catalyst combination, based on the reaction components b) to g) . Further representatives of catalysts and details regarding the mode of action of the catalysts are described in Kunststoff-Handbuch, volume VII "Polyurethane", 3rd edition, Carl Hanser Verlag, Munich/Vienna, 1993 on pages 104-110.

Fillers f) which can optionally be used concomitantly can be either inorganic or organic fillers. Examples of inorganic fillers that may be mentioned are: siliceous minerals such as sheet silicates, metal oxides such as iron oxides, pyrogenic metal oxides such as aerosils, metal salts such as barite, inorganic pigments such as cadmium sulfide, zinc sulfide and also glass, glass microspheres, hollow glass microspheres etc. It is possible to use natural and synthetic fibrous minerals such as wollastonite and glass fibres of various lengths, which can optionally be coated with a size. Examples of organic fillers are: crystalline paraffins or fats, powders based on polystyrene, polyvinyl chloride, urea-formaldehyde compositions and/or polyhydrazodicarboxamides (e.g. derived from hydrazine and tolylene diisocyanate) . It is also possible to use hollow microspheres of organic origin or cork. The organic and inorganic fillers can be used individually or as mixtures. The fillers f) are preferably added in amounts of from 0 to 50% by weight, preferably from 0 to 30% by weight, based on the reaction components b) to g).

Auxiliaries and additives g), which are optionally concomitantly used, include, for example, stabilizers, colour-imparting agents, flame inhibitors, plasticizers and/or monohydric alcohols .

As stabilizers, use is made of, in particular, surface-active substances, i.e. compounds which serve to aid homogenization of the starting materials and are optionally also suitable for regulating the cell structure of the polymers. Mention may be made by way of example of emulsifiers such as the sodium salts of castor oil sulfates or fatty acids and also salts of fatty acids with amines, foam stabilizers such as siloxane-oxyalkylene copolymers and cell regulators such as paraffins. As stabilizers, use is made predominantly of organopolysiloxanes which are water-soluble. These are polydimethylsiloxane radicals onto which a polyether chain composed of ethylene oxide and propylene oxide has been grafted. The surface-active substances are preferably added in amounts of from 0.01 to 5.0% by weight, preferably from 0.1 to 1.5% by weight, based on the reaction components b) to g).

As colour-imparting agents, it is possible to use dyes and/or colour pigments which are known per se for colouring polyurethanes and have an organic and/or inorganic basis, for example iron oxide pigments and/or chromium oxide pigments and pigments having a phthalocyanine and/or monoazo basis.

Suitable flame retardants which may optionally be concomitantly used are, for example, tricresyl phosphate, tris-2-chloroethyl phosphate, trischloropropyl phosphate and tris-2,3-dibromopropyl phosphate. Apart from the halogen-substituted phosphates mentioned above, it is also possible to use inorganic flame retardants such as aluminium oxide hydrate, ammonium polyphosphate, calcium sulfate, sodium polymetaphosphate or amine phosphates, e.g. melamine phosphates.

As plasticizers, mention may be made by way of example of esters of polybasic, preferably dibasic, carboxylic acids with monohydric alcohols. The acid component of such esters can, for example, be derived from succinic acid, isophthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic and/or hexahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic anhydride, fumaric acid and/or dimeric and/or trimeric fatty acids, optionally in admixture with monomeric fatty acids. The alcohol component of such esters can, for example, be derived from branched and/or unbranched aliphatic alcohols having from 1 to 20 carbon atoms, e.g. methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, the various isomers of pentyl alcohol, of hexyl alcohol, of octyl alcohol (e.g. 2-ethylhexanol), of nonyl alcohol, of decyl alcohol, of lauryl alcohol, of myristyl alcohol, of cetyl alcohol, of stearyl alcohol, and/or from naturally occurring fatty and wax alcohols or fatty and wax alcohols obtainable by hydrogenation of naturally occurring carboxylic acids. Further possible alcohol components are cycloaliphatic and/or aromatic hydroxy compounds, for example cyclohexanol and homologs thereof, phenol, cresol, thymol, carvacrol, benzyl alcohol and/or phenylethanol. Additional possible plasticizers are esters of the abovementioned alcohols with phosphoric acid. Phosphoric esters derived from halogenated alcohols, e.g. trichloroethyl phosphate, can optionally also be used. In the latter case, a flame-retardant effect can be achieved together with the plasticizer effect. Of course, it is also possible to use mixed esters of the abovementioned alcohols and carboxylic acids. The plasticizers can also be polymeric plasticizers, e.g. polyesters of adipic, sebacic and/or phthalic acid. Furthermore, alkylsulfonic esters of phenol, e.g. phenyl paraffin sulfonate, can also be employed as plasticizers.

Further auxiliaries and/or additives g) which may optionally be concomitantly used are monohydric alcohols such as butanol, 2-ethylhexanol, octanol, dodecanol or cyclohexanol, which can optionally be used for bringing about a desired termination of the chain.

The auxiliaries and/or additives g) are preferably added in amounts of from 0 to 25% by weight, particularly preferably from 0 to 10% by weight, based on the reaction components b) to g). Further details regarding the customary auxiliaries and additives g) may be found in the specialist literature, for example Kunststoff-Handbuch, volume VII "Polyurethane", 3rd edition, Carl Hanser Verlag, Munich/Vienna, 1993, page 104ff.

The production of the polyurethane foams can in principle be carried out in various ways. It is possible, for example, to work according to the one-shot process or the prepolymer process. In the one-shot process, all components, e.g. polyols, polyisocyanates, chain extenders, blowing agents, catalysts, fillers and/or additives are combined and intensively mixed with one another. In the prepolymer process, an NCO prepolymer is firstly prepared by reacting part of the amount of polyol with the total amount of polyisocyanate, then adding the remaining amount of polyol and optionally chain extender, blowing agent, catalyst, fillers and/or additives to the resulting NCO prepolymer and mixing intensively. For the purposes of the present invention, particular preference is given to a process in which the components b) to g) are blended to give a "polyol component" which is then processed with the polyisocyanate and/or NCO prepolymer a). The chain extenders, blowing agents, catalysts, fillers and auxiliaries and/or additives which may optionally be concomitantly used are generally added as described above to the "polyol component", but this is not absolutely necessary since components which are compatible with the polyisocyanate component a) but do not react with it can also be incorporated into the polyisocyanate component.

The mixture formed on mixing of the reaction components is, for example, applied by the pouring method to the surface of a base formation, in particular to the surface of a ballast bed. Here, the conveying, metering and mixing of the individual components or the component mixtures is carried out using the apparatuses which are known per se in polyurethane chemistry. The amount of the mixture introduced is generally such that the polyurethane foam has a free-foam density of from 20 to 800 kg/m3, preferably from 30 to 600 kg/m3, particularly preferably from 50 to 300 kg/m3. As initial temperature of the reaction mixture applied to the base formation, a range from 20 to 80°C, preferably from 25 to 40°C, is generally selected. The base formation can optionally be dried and heated before introduction of the reaction mixture. Depending on the reaction components, the catalysts added and the temperature conditions, the time until setting of the foam (fibre time) can be from 15 to 45 seconds, preferably from 15 to 30 seconds. Longer setting times are possible .

The reactive components can be mixed by the high-pressure or low-pressure process.

In particular, the protective wall is made essentially closed over its area in the vertical direction and along the boundary line. Parts of the base formation along the boundary line which had not been strengthened by foam are thereby avoided, so that weak points which could allow the protective wall to be broken through are avoided. In particular, the foam of the protective wall is essentially homogeneous in the vertical direction and/or along the boundary line and/or foam subsequently formed has foamed around previously formed foam. The foam formed later can, in particular, have penetrated into pores of the previously formed foam and thereby brought about an essentially physically locked bond. It is also possible for foam formed later to enclose the previously formed foam in an essentially half-moon fashion, so that foam layers arranged in succession in the vertical direction and/or along the boundary line can form shell-like enclosures. This leads, in the case of loading of the protective wall laterally to the boundary line, to the foam formed later being held firmly by physical locking onto the previously formed foam and not being able to slide off from the previously formed foam under load. A high stability of the protective wall is maintained as a result.

The protective wall preferably has an average extent in the vertical direction of H and a distance d up to the surface, where -0.05 < d/H < 0.30, in particular -0.01 < d/H < 0.20, preferably -0.00 < d/H < 0.15 and particularly preferably -0.05 < d/H < 0.10. Here, a negative value of the ratio d/H means that the protective wall projects from the base formation to above the level of the surface of the base formation, while a positive value of the ratio d/H means that the protective wall remains in the base formation underneath the level of the surface of the base formation. As a result of the protective wall extending essentially to the surface of the base formation, satisfactory securing of the civil engineering site can be achieved. When the protective wall projects from the base formation, this results in a projecting periphery which can be used as additional safety measure and/or makes it possible to heap up material removed from the civil engineering site in the vicinity of the protective wall. When the protective wall remains somewhat below the surface, a generally insignificant part of the retained base formation can trickle into the depression produced during removal in the region of the civil engineering site, so that satisfactory securing of the civil engineering site can be achieved with a small usage of material.

The seeping of the reactant mixture into the base formation particularly preferably occurs purely as a result of gravitational force. Pressing of the reactant mixture into the base formation is not necessary. In particular, it is not necessary to provide a lance or a comparable aid at a level below the surface of the base formation in order to introduce the reactant mixture into the base formation. Instead, the reactant mixture can penetrate solely under its own weight into the hollow spaces of the base formation and, if necessary, displace liquids, in particular water, present there.

The foaming preferably takes place after a starting time T after the application of the reactant mixture to the base formation, where, in particular, the starting time is selected, in particular, by setting the reactivity of the reactant mixture with the aid of a catalyst, while taking into account a rate of seepage of the reactant mixture into the base formation to achieve a minimum height of the protective wall in the vertical direction. The seeping rate is, in particular, determined decisively by the porosity of the base formation and the viscosity of the reactant mixture. The porosity of the base formation can, in particular, be determined by taking off test specimens from the base formation to be secured and examination thereof. In particular, the seepage rate can be determined by empirical experiments using an intended reactant mixture and the test specimen taken from the base formation to be secured. Values based on experience are preferably available for various soil types of base formations having comparable particle size distributions, for example ballast bed of a railway track system or natural earth, so that separate experiments can be saved. When the base formation is formed by a ballast bed, the starting time T can, in particular, be selected so that 1 s < T < 30 s, preferably 3 s < T < 20 s and particularly preferably 5 s < T < 10 s. When the base formation is formed by a soil which has arisen naturally, the starting time T can, in particular, be selected so that 2 s < T < 120 s, preferably 5 s < T < 60 s and particularly preferably 10 s < T < 30 s.

The average location at which the reactant mixture is applied to the surface of the base formation is particularly preferably displaced along the boundary line with a substantially constant speed. In this way, a substantially homogeneous composite of the protective wall in the vertical direction and along the boundary line can be brought about. It is here possible, for example, for the application of the reactant mixture to occur in such a way that the application of the reactant mixture oscillates about a midpoint, with this midpoint being displaced at a substantially constant speed along the boundary line. In this case, the midpoint defines the average location at which the application of the reactant mixture occurs. In particular, the location at which the application of the reactant mixture occurs is defined by an outlet through which the reactant mixture leaves a stock chamber or the like. For example, the outlet can be a projecting end of a nozzle which projects from a mixing chamber in which the components of the reactant mixture are mixed with one another .

In particular, a pre-solidified part of the protective wall has partially foamed around it a reactant mixture which is caused to seep subsequently along the boundary line. This makes it possible for foam formed later to enclose the previously formed foam in an essentially half-moon fashion, so that foam layers arranged in succession along the boundary line can enclose one another in a shell-like manner. This leads to the foam formed later being held firmly by positive locking on the previously formed foam in the case of loading of the protective wall laterally to the boundary line and not being able to slide off on the previously formed foam under load. A high stability of the protective wall is maintained in this way. This can be particularly advantageous when a low rate of seepage is to be expected for the reactant mixture applied to the surface of the base formation and/or the protective wall is to penetrate particularly deeply into the base formation.

The protective wall is preferably introduced into a ballast bed of a railway track system. The ballast bed of a railway track system is comparatively highly porous and has comparatively large intermediate spaces between the ballast stones, so that the reactant mixture can easily attain a great seepage depth in a short time. In particular, for example in the case of renovation of a railway track system, the protective wall can be provided with a time offset to a load removal region of a ballast bed, so that the ballast bed can be removed in the course of renovation. Preference is given to two parallel tracks being provided, with the protective wall being provided between the tracks. This makes it possible for the ballast bed of the one track to be removed first for renovation and the removed ballast bed subsequently to be tipped on again, with the ballast bed of the other track being able to be removed for renovation after the renovation of the one track. The protective wall can here be used for the renovation both of the one track and also of the other track, with the protective wall being able, in particular, to perform a protective function both during removal of the ballast bed and also during the subsequent tipping-on of the renovated ballast bed.

Particular preference is given to a rail vehicle for stocking the reactant mixture being moved along a track, with the protective wall being produced laterally alongside the track. The rail vehicle can also transport relatively large amounts of the components of the reactant mixture in coupled wagons, so that a particularly long, in particular essentially continuously produced, protective wall can be provided in the ballast bed of the railway track system without a great outlay.

The invention further provides a protective wall for securing a civil engineering site, which can be produced by a method which can be configured and developed further as described above. The protective wall comprises, in particular, cured foam and parts of the base formation surrounded by the foam. The protective wall comprises, in particular, ballast stones at least partially surrounded by foam. The protective wall is, in particular, substantially homogeneous in the vertical direction and/or along the boundary line, i.e. without visually discernible boundary layers between various regions of the foam. The homogeneous composite of the protective wall comprising cured foam and part of the base formation surrounded by the foam in the vertical direction and/or along the boundary line which is made possible thereby enables unnecessary phase boundaries and/or weak points to be avoided, so that the protective wall has increased stability and stable securing of the civil engineering site is made possible even in the case of a porous and hard base formation, in particular in the case of a ballast bed of a railway track system.

The protective wall has, in particular, a length L along the boundary line of 1 m < L, in particular 5 m < L, preferably 10 m < L and particularly preferably 50 m < L. Particularly when the protective wall is provided in a ballast bed of a railway track system, the result may be lengths L which can in principle extend over the entire length of the line of the railway track system. For example, the protective wall has a length L along the boundary line of 100 m < L, in particular 1 km < L, preferably 10 km < L and particularly preferably 50 km < L. The protective wall has, in particular, a height H in the vertical direction of 20 cm < H < 5 m, preferably 40 cm < H < 3 m, more preferably 60 cm < H < 2 m and particularly preferably 80 cm < Η < 1 m. The protective wall has an average thickness d transverse to the boundary line of, in particular, 1 cm < d < 50 cm, preferably 2 cm < d < 40 cm, more preferably 5 cm < d < 30 cm and particularly preferably 10 cm < d < 20 cm.

In the following, the invention will be illustrated by way of example with reference to the accompanying drawings for a preferred working example; the features presented below can, both individually and in combination, represent an aspect of the invention. The figures show:

Fig. 1: a schematic sectional view of a railway track system and

Fig. 2: a schematic sectional view of the railway track system of Fig. 1 with a civil engineering site.

The railway track system 10 depicted in Fig. 1 has, in the working example depicted, a first track 12 and a second track 14, with the first track 12 resting on a base formation in the form of a first ballast bed 16 and the second track 14 resting on a base formation in the form of a second ballast bed 18. For example, the second track 14 together with the associated second ballast bed 18 is to be removed for renovation purposes. However, without safety measures, the first ballast bed 16 would slide away laterally on removal of the second ballast bed 18, as a result of which the first track 12 would no longer be sufficiently supported and could not be travelled on for safety reasons. At the same time, there is not enough space between the first track 12 and the second track 14 for a sufficient banking angle to be able to be provided for the first ballast bed 16 after removal of the second ballast bed 18.

Instead, a reactant mixture 24 is poured onto a surface 26 of the ballast beds 16, 18 by means of a first rail vehicle 20 provided on the first track 12 and/or a second rail vehicle 22 provided on the second track 14. The rail vehicles 20, 22 can, in particular, be moved at a constant speed on the associated track 12, 14 so that the reactant mixture 24 can be poured out along a boundary line 36 between the remaining first ballast bed 16 and the second ballast bed 18 to be removed. The reactant mixture 24 can, for example, be mixed in a mixing chamber 28 and discharged via a nozzle 30. The reactant mixture 24 can seep into the ballast beds 16, 18 down to a base level 32 down to which the second ballast bed 18 is to be removed. The reactant mixture 24 can begin to foam on reaching the designated base level 32 and form a composite with the ballast stones of the ballast beds 16, 18. The foam 34 formed by a chemical reaction of the reactant mixture 24 can here grow from below from the base level 32 upward to approximately the surface 26.

As shown in Fig. 2, the foam 34 can solidify and together with the ballast stones of the ballast beds 16, 18 which have become embedded in the foam form a protective wall 38 which can have a slightly trapezoidal cross section. The protective wall 38 has a stability which is great enough to prevent the first ballast bed 16 from sliding into the region of a civil engineering site 40 when, for example, the second ballast bed 18 has been removed by means of a suitable construction machine 42. This means that the protective wall 38 presses an outer side face 44 which faces away from the civil engineering site 40 against the first ballast bed 16 and has an inner side face 46 facing the civil engineering site 40, which face can be exposed. Between the outer side face 44 and the inner side face 46, the protective wall 38 has a thickness which is sufficient to be able safely to bear the loads acting on the protective wall 38. Subsequently, the second ballast bed 18 can preferably be tipped on again and the first ballast bed 16 can be removed, with the same protective wall 38 being able to be used for supporting the second ballast bed 18, with the outer side face 44 and the inner side face 46 then being exchanged. Renewed production of the protective wall 38 can be saved in this way. Furthermore, either the first track 12 or the second track 14 remains able to be travelled on during the renovation work on the respective other track 14, 12 as a result.

The above-described method is also applicable to a base formation different from a ballast bed 16, 18, for example a natural soil. The method can, for example, be employed in road construction, tunnel construction, excavation work, production of a cellar or other construction work having civil engineering aspects or civil engineering-related aspects.

Claims

A method for securing a deep building site (40), comprising the steps of: applying a reactant mixture (24) continuously along a boundary line (36) defining the deep building site (40) on a surface (26) of a bottom formation , in particular a ballast bed (16, 18), to allow the reactant mixture (24) to penetrate into the bottom formation (16, 18) and to foam the reactant mixture (24) into a solidified foam (34), which foam (34) and a portion of the bottom formation (16, 18) surrounded by the foam (34) forms a protective wall (38) extending along the boundary line (36) to retain a bottom formation (16) provided on an outer surface (44) of the protective wall 38, in the event that the bottom formation (18) is removed from an inner side surface (46) of the protective wall 38.

The method of claim 1, wherein the protective wall (38) is configured to be substantially flat in the vertical direction and along the boundary line (36).

The method of claim 1 or 2, wherein the protective wall (38) has an average vertical extension from H to the surface (26) at a distance d, where -0.05 d / H <0.30, in particular - 0.01, d / H, 0.20, preferably 0.00 <d / H <0.15, and most preferably 0.05 ^ d / H ^ 0.10.

A process according to any one of claims 1 to 3, wherein the penetration of the reactant mixture (24) into the bottom formation (16, 18) takes place solely by gravity.

A method according to any one of claims 1 to 4, wherein the foaming takes place after a start time T after applying the reactant mixture (24) to the bottom formation (16, 18), in particular the start time, especially by adjusting the reactivity of the reactant mixture (24). using a catalyst selected taking into account the penetration rate of the reactant landing (24) in the bottom formation (16, 18) to obtain a minimum height of the protective wall (38) in the vertical direction.

The method according to any one of claims 1 to 5, wherein the average location at which the reactant mixture (24) is applied to the surface of the bottom formation (16, 18) is displaced along the boundary line (36) at a substantially constant rate.

The method of any one of claims 1 to 6, wherein a previously solidified portion of the protective wall (38) has a partially foamed reactant mixture (24) around it which is subsequently allowed to penetrate along the boundary line (36).

A method according to any one of claims 1 to 7, wherein the protective wall (38) is inserted into a ballast bed (16, 18) of a railway track system (10).

The method of claim 8, wherein a rail vessel (20, 22) for storing the reactant mixture (24) is moved along a rail track (12, 14), wherein the protective wall (38) is formed adjacent to the rail track (12, 14).