GB2132661A - A process for solidifying and waterproofing underground structures - Google Patents

Abstract

A process for solidifying and making watertight underground and other building structures, artefacts (especially conduits, pipes and canals), rocks and soil, utilising an aqueous water glass solution and fluosilicic acid. In, on or in the vicinity of the object to be treated water glass solution is brought into contact with fluosilicic acid in the presence of 0.01-1 part by weight %, expediently 0.05-0.2 part by weight, of a hydrogel-forming water-soluble organic polymer and a cross-linking agent for the polymer, calculated on one part by weight of solid material in the water glass solution. The thus formed gels are resilient as well as suitably solid and strong and provide very good water-tightness.

Description

SPECIFICATION A process for solidifying and waterproofing underground and civil engineering structures, artefacts, especially canals, and conduits, constructional elements, rocks and soils The invention concerns an improved process for solidifying and waterproofing underground and civil engineering structures, artefacts, especially canals, and conduits, constructional elements, rocks and soils, by utilising water glass or water glass-containing media.

In the sense of the invention the terms "structure" "artefact", "constructional element", " structural element", "rock" and "soil", are to be understood in the widest possible sense; these terms also include various storage basins, tunnels, natural or artificial cavities, soil and rock discontinuities.

It is known that the water-tightness of underground constructions and structural elements, especially canals, conduits and basins is generally imperfect. The defects can be traced back in the main to faults in the manufacture and assembly of the parts, and to cracks and other deterioration in the state of the structural elements that develop during use. It is also known that the repair of building and underground structural elements and artefacts (primarily underground canal and conduit networks and pipes) is an extremely timeconsuming, expensive and labour-intensive operation, and moreover, in many cases the repair cannot be carried out with the desired result.

Hungarian Patent Specification No. 153,975 describes a simple and rapidly performable process for solidifying and waterproofing underground structural elements, artefacts, building elements, rocks and soils etc., In accordance with what is described in that specification, water glass or a water-glassy medium is applied to, into or in the vicinity of the object to be repaired, then the said medium is subjected to the effect of a gaseous fluoride, more precisely hydrofluoric acid, silicon tetrafluoride and/or fluosilcic acid, (H2SiF6). On contact with the gaseous fluoride, the water glass gels in a short time and completely seals cavities, gaps or cracks. When this process is carried out for water proofing structural elements or artefacts, e.g.

underground canals, conduits or ducts, a further advantage is afforded by the fact that the water glass passing into the soil through the cracks also solidifies and so improves the bedding of the construction or artefact and solidifies the surrounding soil. A very advantageous additional effect of the utilisation of gaseous fluorides is that they improve the corrosion resistance of concrete and ferro-concrete structures.

Despite its numerous advantages, this process has not come into widespread use. One factor which significantly hinders the introduction into use of this process is that the treatment gases hydrofluoric acid and silicon tetrafluoride are both highly toxic and so their use is not recommended from an ecological point of view. A further disadvantage is that the silica gel that is formed is not resilient and cannot "follow" displacements of the treated object or soil stratus. The silica gel does not sufficiently swell under the effect of the water and thus cannot satisfactorily seal any new cracks that may form next to the gel plug due to displacements.

According to our earlier Hungarian patent application No. MA-2924, water-glass as gelforming material is replaced by various organic polymers, primarily acrylic acid and acrylamide polymers, optionally in the presence of inert particulate solid fillers. The thus formed gels are sufficiently resilient and swell to a satisfactory extent under the effect of water, but their disadvantage is that they are relatively soft and cannot support great mechanical loads. A further disadvantage is that most of the polymers to be used are expensive and difficult to obtain and in certain cases, their application technology requires special expertise and apparatus.

Accordingly, a new process is needed which combines the advantages of the known processes but is free or substantially free from their disadvantages. In the course of experiments, we have found that if one proceeds essentially in the manner disclosed in Hungarian patent No.

1 53,975, but for the gel-forming system we also add as a further component certain organic polymers, then suitably strong, while at the same time suitably resilient, gels can be formed by a simple and rapidly applicable technology, which gels render the object to be treated permanently solid and water-proof.

The aim of the invention is therefore the provision of a process for the solidification and waterproofing of underground structures, buildings, artefacts, structural elements, rocks,~ and soils, utilising an aqueous water glass solution and fluosilicic acid.

In accordance with the invention one proceeds by bringing the water glass solution into contact with fluosilicic acid in the presence of 0.01 to 1 part by weight, expediently 0.05--0.2 part by weight, (calculated on one part by weight of solid matter in the water glass solution) of a gelforming, water-soluble organic polymer and an agent for promoting the cross-linking of the polymer.

In the description and claims, the term "water glass" is intended to cover alkali metal silicates and ammonium silicate. The most expedient water glass is an aqueous sodium silicate solution having a dry matter content of 35% by weight.

The expression "gel-forming, water soluble organic polymer" is meant to cover hydrogelforming organic polymers which can be mixed with water without limit and which are in a liquid state. One type of such organic polymers is the polyelectrolytes, of which the most advantageous representatives are the carboxylate-type (i.e.

containing a QOOX group) polymers, wherein X is a monovalent cation. Amongst these may e.g.

be mentioned carboxymethyl cellulose, polymers and co-polymers of acrylic acid and methacrylic acid, partially hydrolysed polyacrylamide and polyacryiic acid esters which have been mostly hydrolysed as well as their alkali metal and ammonium salts. Another type of organic polymer is formed by hydrogel-forming non-ionic polymers, of which the most important representatives are polyacrylamides and polyvinyl alcohol.

Cross-linking agents for the polymer are wellknown in plastics chemistry and will not therefore be described in detail. Merely in general, we would mention that polyelectrolytes may most expediently be cross-linked by using polyvalent metallic ion-containing compounds e.g. salts of calcium, magnesium, iron, copper and chromium while for cross-linking non-ionic polymers, expediently polyvalent aldehydes, e.g. glyoxal or glutaraldehyde may be used.

In given cases the cross-linking agent for the polymer may already be present in the treatment space. A typical case of this is where for treating objects disposed in or soaked through by ground water, a polyelectrolyte-containing gel-forming system is used, since ground water always contains polyvalent metal compounds which after a time assure the desired degree of cross-linking.

The above-mentioned cross-linking agents also promote the gelation of the water glass at varying rates and extent. In this way they promote the mutual integration or combination of and the formation of chemical bonds between the two gel matrixes.

The fluosilicic acid (HzSiF6) used in the gelation may in given cases also contain small amounts of various other fluorides, e.g. hydrofluoric acid or silicon tetrafluoride as contaminants. For the purpose of gel-formation, one may very advantageously utilise the contaminated aqueous hydrogen fluosilicic acid solution formed as a waste product in the manufacture of phosphate fertilisers; the fluosilicic acid may also be used in gaseous form, but it is more advantageous if it is brought into contact with the other components of the gel-forming system in the form of an aqueous solution.

The individual components of the gel-forming system may be added in one by one, but one may proceed more advantageously if the gel is formed by the interaction between two material streams.

Of these, one is the aqueous solution of water glass, while the other is the fluosilicic acid or its aqueous solution. The water-soluble gel-forming organic polymer is added, with due regard to the compatibility conditions, to one or other of both of the material streams. The polyelectrolyte type of polymers do not dissolve in the aqueous fluosilicic acid solution and therefore these must be added to the water glass solution. The non-ionic polymers are advantageously added to the acid solution, while the polyacrylamide and the relatively little-hydrolysed (maximum 15%) polyacrylamide may be added equally to the water glass solution and to the acid solution.In the case where the agent promoting the cross-linking of the polymer is not already present at the treatment site, e.g. where a polyelectrolyte type polymer is used for treating objects which are not in contact with ground water, or if non-ionic polymers are used, this material may be added to an aqueous solution of fluosilicic acid. The nonionic polymers do not gel in the aqueous silicic acid solution even in the presence of a crosslinking agent (polyvalent aldehyde), hence one need not fear any technological complications.

It is to be noted that the aqueous fluosilicic acid solutions formed as waste in the manufacture of the phosphate fertilisers generally already contain a sufficient quantity of polyvalent metal compound. A given metallic ion concentration should expediently be adjusted or set for a good reproducibility and controllability of the gelation process.

The material streams may be brought into contact with each other in any desired sequence.

Thus, for example, one may proceed by first applying the water glass solution to, or to the vicinity of the object to be treated, the solution optionally also containing a gel-forming watersoluble organic polymer, and thereafter the acid solution is applied which in given cases may also contain the required further components such as the non-ionic polymer and/or the cross-linking agent. In the case where, with the exception of the fluosilicic acid, all the required further components are present in the water glass solution or are present at the treatment site, e.g.

where the treatment is performed at a site permeated through with ground water and the water glass solution contains a polyelectrolyte then the fluosilicic acid may be contacted with the further components of the gel-forming system in its gaseous state. Naturally, one may also proceed by first passing the acid material stream to the site of the treatment and thereafter introducing the water glass material stream; however, this procedure is less advantageous than the one described above. If required, the treatment may be repeated once or several times.

Expediently, the fluosilicic acid is used in an excess quantity in relation to that required for the gelling of the water glass component. When this is required for environment-protecting considerations, the excess acid may be simply neutralised at the site of application by applying there an alkaline material. As an alkaline material one may particularly advantageously use water glass solution which may in given cases also contain a gel-forming water-soluble organic polymer milk of lime, dilute sodium carbonate solution etc., This after-treatment may expediently be combined with the testing of the watertightness of the repaired or improved artefacts.

The process according to the invention may advantageously be combined with the technical solutions described in the above-cited earlier Hungarian patent application and Hungarian patent. In accordance with a particularly advantageous method, silica gel is formed at the treatment site in accordance with the procedure described in Hungarian patent No. 153,975 from a water glass solution and fluosilicic acid and then as a second operation or step, the process according to the invention is performed.

Where it is desired completely to seal or block large-volume gaps or cavities in accordance with the method of this invention, then in a previous step, the gaps or cavities may be charged with a particulate solid material which does not impede the gel-forming reaction, e.g. perlite, quartz sand, fly ash etc., or such material may be mixed with either of the aqueous materials streams.

In order to improve the resilience and deformability of the resulting gel, the gel-forming system may also be combined with rubber latex.

In this case one proceeds by applying onto, into or in the vicinity of the object to be treated a natural or synthetic rubber latex which is then either allowed to coagulate spontaneously or is coagulated with an acidic material, and only then is the above-described water glass fluosilicic acid treatment performed. However, one may also proceed by adding to the water glass solution calculated on one part by weight solid material, an amount of natural or synthetic rubber latex which corresponds to 0.005-1 part by weight, expediently 0.05-0.2 part by weight, of solid material, and this mixture is brought into contact with the fluosilicic acid in the presence of a hydrogel-forming water-soluble organic polymer.

In the course of the process according to the invention, a homogeneous, perfectly "builttogether" gel system containing both organic and inorganic structural components is formed from the water glass and from the optionally present rubber latex as well as the hydrogel-forming water-soluble organic polymers This gel structure or system preserves the original strength of the inorganic silicate component while at the same time remains resilient in a manner characteristic of the organic component and thus provides a perfect water-proofing and solidifying effect.This result was not foreseeable from the present state of the art, because the rate of gel formation and the optimal conditions for gelling of the organic and inorganic gel-forming materials significantly differ from each other and thus one would have expected rather that at the treatment site two separate gel systems would form which would mutually deleteriously influence each other's properties.

The method according to the present invention is described purely by way of illustration, in greater detail in the non-limiting Examples below.

Example 1 A glass tube of 30 cm length, 4 cm inner diameter is provided at its bottom end with an apertured rubber stopper. Sand of maximum 2 mm particle size is charged into the tube to a height of 20 cm.

A gauze sheet is placed on the rubber stopper.

90 ml concentrated (35%) water glass solution is poured onto the sand column. This solution soaks completely through the sand column and then at the bottom the excess begins to drip out. When the excess water glass solution is just absorbed at the top of the sand column, the column is charged with a mixture of 40 ml concentrated aqueous fluosilicic acid solution, 40 ml of 5 weight % aqueous polyacrylamide solution and 10 ml concentrated aqueous glyoxal solution. This aqueous solution gradually penetrates into the sand column steeped in the water glass, mixes there with the water glass, and then the gel formation commences. After completion of the gelation, the excess acid solution can no longer be absorbed in the column and the ungelled waterglass cannot drop out at the bottom.The excess acid solution is poured away then the rubber stopper is removed andthe sand is washed under a tap with a strong water jet. The gel part will resist the water jet while the part which has not gelled but which is steeped in the water glass will be washed out.

In the course of the experiment, the 20 cm long sand column will remain behind as an 8090% solid, dense and completely water-tight, gelled charge; subjected to a pressure of a water head of 1.5 m for 1 hour, the water level drop is at most 5 mm.

When in the course of the experiment, 90 ml of concentrated aqueous fluosilicic acid solution was applied to the water glass soaked column, without applying other components, the gelled column length was reduced to 3-5 cm. The watertightness of the charge was unsatisfactory; under a water head of 0.1 m for 30 minutes, the water level drop was 50 mm.

When in the course of the experiment there was applied to the water-glass soaked column 90 ml of aqueous fluosilicic acid solution diluted with water in a 1:1 weight ratio, without containing other components, the gelled column length was 5-10 cm. The charge had poor watertightness: under a water head of 0.1 m for 10 minutes, the water level drop was 70 mm.

Example 2 The experiment described in Example 1 was repeated but the sand column was first soaked through with a mixture of 80 ml concentrated water glass solution and 10 ml of sodium polyacrylate solution of 10 weight % solid matter content; and then a mixture of 40 ml concentrated aqueous fluosilicic acid solution, 40 ml water and 10 ml 10% iron (Ill) fluoride solution was applied to the column. The result was a dense, impact-resistant pressure-resistant perfectly watertight charge. At a water head of 1.5 m, the water level drop was negligible.

Example 3 The experiment described in Example 1 was repeated but the sand column soaked through with water glass solution received a 90 ml aqueous solution containing 5 weight % fluosilicic acid, 5 weight % polyvinyl alcohol and 1 weight % boric acid. A charge of the same quality as that described in Example 1 was obtained.

Example 4 The experiment described in Example 1 was repeated but as a preceding step a mixture of 60 ml of concentrated water glass solution and 30 ml of 6 weight % of a 10% hydrolysed aqueous polyacrylamide solution was applied to the sand column, then a 90 ml aqueous solution containing 5 weight % of fluosilicic acid and 2.5 weight % of chrome alum are applied to the sand column. A charge of outstandingly good mechanical properties was obtained, with watertightness qualities identical with those described in Example 2.

Example 5 The experiment described in Example 1 was repeated but in a preceding step the sand column was soaked through with a mixture of 67.5 ml solid water glass solution, and 22.5 ml of 10% aqueous sodium polyacrylate solution, then a 90 ml aqueous solution containing 10 weight % fluosilicic acid, 5 weight % polyacrylamide and 1 weight % glyoxal was applied to the column. The resulting charge had the same characteristics as those described in Example 2. The strength of the charge grows with time if the charge is soaked in ground water because under the effect of the polyvalent metal ions present in ground water, the degree of cross-linking of the sodium-polyacrylate is increased.

In the following Examples, reference will be made to the accompanying, purely schematic drawings representing cross-sectional views of underground structures to which the method of the invention may advantageously be applied.

Example 6 In the case illustrated in Figure 1, a conduit or canal section between two shafts 2 and 3 is subjected to treatment simultaneously via the shafts. The second is assumed to have been previously cleaned and is then closed at the shafts by means of closure members 1. Thereafter, the section is filled from a tank 4 via shaft 2 with an aqueous water glass solution of 35.7-38.0 Bye'0.

The injection pressure required for the solution to reach pores, crackes, cavities, faulty fittings runs, loose or porous pipe walls 5, is produced by the head "m". This pressure head "m" will depend on the extent or magnitude of the fault but is expediently 1-2 metres which may in given cases be assured by topping up, When the water glass level no longer drops in the shafts, or the drop is of a small magnitude, (this in general takes place in 20-60 minutes, depending on the extent/size of the faults), the water glass solution present in the section is pumped as fast as possible typically under 5-10 minutes, back via the shaft 2 into the tank 4.

Thereafter, in the manner illustrated in Figure 2, an acid solution is passed from a tank 6 via shaft 2 into the section. The acid solution is a mixture of 1 part by weight concentrated (nearly 20 weight %) industrial aqueous fluosilicic acid solution and 1 part by weight 5 weight % aqueous polyacrylamide with a degree of hydrolysation of 10% and to this mixture 1 weight % chrome alum related to the total weight of the mixture is also added. The acid solution is passed into the canal/conduit section in the shortest possible time, 5-10 minutes, in order to minimize expelled or injected-out water glass streaming back into the section. The pressure head "m" of the acid solution is expendiently adjusted to be 0.5-1.0 m higher than the pressure head "m" of the water glass solution.The required height of the solution is assured by topping up with further amounts, as necessary.

When the level of the solution no longer drops in the shafts, which in general takes place after 20-60 minutes, the solution is pumped back via the shaft 2 into the tank 6. The repair of the section has now been accomplished.ln the case where the level of the acid solution no longer drops in the shaft after 15 5 minutes, or drops only to an extent permitted by the prescribed standards of the watertightness tests, the necessary watertightness of the section has been attained. Thus, while accomplishing the repair, the watertightness of the channel is simultaneously examinable or testable, and thus one may avoid the post-repair, discrete testing normally carried out with water or air. After removing the closure members, the section can be put back in operation.

The material which in the course of repair penetrates into the leakage or seepage runs, cracks and cavities, or which is expressed through discontinuities, poor fits, cracks, etc., gels, solidifies and forms an in situ watertight layer 5.

In this way, therefore, not only are the leakage or seepage runs of the conduit perfectly sealed but also the surrounding soil is rendered watertight and more solid. Thus, the embedding of pipelines may significantly be improved, which is of decisive importance from the point of view of the service life and rigidily of a pipe network.

For transporting the water glass, charging it into the sections to be repaired and pumping it back, slurry-pumping vehicles of 3.5-10 m3 may be used. For transporting the acid solution, charging it into the sections as well as pumping it back, corrosion-resistant apparatuses such as plastic tanks and corrosion-resistant pumps etc., should be used.

At the beginning of a conduit section replacement operation, the section separated from the rest of the system by the closure elements and filled with a water glass solution may also be used as a substitute or replacement for the fault-diagnostic pressure tests currently performed with water, which is an extra advantage. This is because the currently performed pressure tests using water, result in an undesirably large quantity of water passing into the ground which may cause further collapses or the formation of cavities and thus lead to further damage. In the process according to the invention, the water glass filtering out into the soil does not cause such problems because its viscosity is significantly higher than that of water and because its character is fundamentally different from water.

In accordance with computations not detailed here, and in dependence upon the temperature, the viscosity of the water glass solution employed etc., for the same pressure head "m" (and also taking into account the higher specific gravity of the water glass solution), approximately 10 to 1 6 times more water would flow away in the conventional aqueous pressure test then the amount of water glass solution passing into the soil.

Another great advantage of the process according to the invention is that repair may also be undertaken of a section that extends between three or more shafts together with their associated spur lines to dwelling houses, waterabsorbing shafts, ducts and roof manifolds. This is because the process according to the invention enables these pipes or ducts to be repaired while repairing the canal section. Thus, depending on the apparatus used, on the available quantities of the treatment solutions and the internal dimensions of the section to be repaired, one can perform in one step the repair of a section the length of which may be between 30 to 100 metres.By suitable organisation and with suitable experience, utilising mass production methods, in one 8-hour shift, 2-3 repair cycles may be performed such that, for instance, the solution pumped back from the section repaired in the first cycle is charged into the section to be repaired in the second cycle and then the solution pumped back from there is fed to the section to be repaired in the third cycle.

The process according to the invention affords the following important additional advantages in the course of repairing conduits, canals, pipes or ducts: - the whole technological process for repair may be mechanised with relatively little expense and apparatus; - the amount of actual "live" labour required is relatively low whilst the speed of repair is very high, - the method hardly hinders or disturbs traffic as it is not necessary to disturb the road surface; - the process is not accompanied by any hazard of explosion or fire; - the repair does not make the hydraulic properties of the canal or duct worse; - the repaired channel does not involve any additional maintenance costs; and - the process is also suitable for repairing ducts disposed in ground water, which case the pressure head "m" is calculated from the level of the ground water.

The water glass solution and acid solution pumped back from the section after repair may be re-used several times, without limitation of time.

Since according to the invention the repair is performed with liquid solutions, it is not necessary first to open up the sites of faults. Such opening up is a very expensive, time-consuming and labour-intensive process. The solutions automatically find the fault locations and eliminate the faults.

The process according to the invention is also suitable for repairing discrete faults in the conduit sections, such as poor pipe fittings. In this case it is not necessary to fill up the whole section to be repaired; instead, with the aid of a suitable and known apparatus, the solution is applied only at the desired location(s). In this case, in general it will not be necessary to disconnect the section during repair from the network: the waste waters arriving through the section may be conveyed further.

Even where the method employed is one of those that uses filling up, it can be achieved that the section remains operative during repair. Thus, for instance, one may proceed by lifting over (by passing) the effluent arriving from the shaft upstream of the section under repair; one may also proceed by placing an appropriately resilient pipe within the section under repair and filling up, which pipe amounts to approximately one-half of the internal dimensions of the section to be repaired. In the course of utilising methods involving filling up the section under repair, in most cases it will not be necessary to by-pass or transfer the effluent because the repair takes such a short time that the swelling or damming caused by the closure of the section does not cause any problems.

When it is desired simultaneously to repair several sections between the shafts and, in order to reduce the amount of the treatment solutions it is not desired to fill up one of the intermediate shafts, then these shafts may be closed on the supply and delivery side with pipe closures which have a through-going pipe.

A further advantage of a technology using two liquids is that no gas can pass into the environment through any undetected connections.

Example 7 Where it is desired to pay particular care and attention to minimise the amount of water glass solution flowing back into the section between the time of pumping back the water glass solution and the filling up with the acid solution, one may proceed as shown in Figure 3.

Before commencing the treatment and after locating the members 1, hermetic closure cover plates 7 and 8 provided with suitable throughgoing apertures and bypass fittings are placed in the shafts. The plates are suitably loaded against the lifting effect of an overpressure of air that may arise in the canal or are secured to the shafts.

Thereafter, in accordance with what is described in Example 6, the section is filled with a water glass solution from tank 4 while the valves 11 and 1 2 associated with plates 7 and 8, respectively are open. When the pumping back of the solution 2 to tank 4 is commenced, the valves 11 and 12 are closed and with the aid of the air-compressor 13 compressed air is passed via line 14 into the shaft section so that an overpressure of 0.2 atmospheres is formed in the section, monitored by a gauge 9.

At this time a valve 1 5 is kept open while another valve 1 6 is closed. When the water glass solution has been pumped back, the valve 15 is closed the valves 11, 12 and 16 are opened and the acid solution from tank 1 7 fills the section via the line 14. The further stages of the repair process are identical with those described in conjunction with Figure 2.

Example 8 In Figure 4 there is shown a technical solution suitable for repairing larger section canals wherein the complete filling of the whole section with a solution is no longer economic or is too complicated. The section is closed with valves 18 and 19, then an inflatable plastic hose 22 provided with spacers 21 is placed in position via a line 20. The solutions used for filling the section as well as the repair procedure thereafter agrees with that described in Example 6.

Example 9 The process according to the invention may be extremely advantageously utilised for repairing channels made from bricks. Particularly good results can be achieved in repairing older, mortarbound brick channels. In these channels, under unfavourable conditions, the mortar relatively quickly deteriorates and under the effect of the water filtering in or out, cavities are formed behind the bricks and the conduits or ducts can collapse or break in. This may frequently lead to a collapse of the road surface also.

The repair is carried out in accordance with the description given in Example 6 or Example 8. The repaired section is shown in Figure 5. As may be seen from Figure 5, in the course of the repair, the solution fills the cavities, runs, gaps 5 and after gelling it in effect glues together the bricks and walls. In addition, the treatment provides complete waterproofing.

Example 10 Figure 6 shows the repair of a faulty, nonwater-proofed closed basin disposed in ground water.

After suitable cleaning the basin is filled with a water glass solution of the concentration given in Example 6, via an opening provided on the basin.

If required, because of leakage out (exfiltration) the level of the solution in the basin is maintained constant by topping up. When the exfiltration of the solution has greatly decreased or has ceased (which, in dependence on the extent of the fault, may generally take place in 30-120 minutes), the solution is removed in the manner described in Example 6, and is then filled with an acid solution having the composition described in Example 6. When the exfiltration or level drop of the solution has ceased, or its magnitude dropped below a prescribed threshold value, generally after 20-120 minutes, the acid solution is removed in the manner described in Example 6.

The solution penetrating into and through gaps and cracks gels outside the wall of the basin and the thus formed stoppers or bungs 23 of gel together with gel-containing soil layers assure a perfect watertightness for the basin. If desired, before filling up the basin, a volume-reducing element may be placed in it, in accordance with the description given in Example 8.

Example 11 The process according to the invention is also suitable for the stabilisation of leaning or cracked structures, artefacts and buildings. Figure 7 shows a toppled or leaning ferro-concrete water tower and its manner of stabilisation. In the vicinity of base bodies 24 an appropriate number (e.g. 4 per base body) of perforated injection tubes 25, known and used in soil solidification technology are pile-driven into the ground to a desired depth. Thereafter, with the aid of a pump, and with due regard to the prescriptions and soil conditions, e.g. 80 litres of water glass solution per pipe are pressed into the soil. During this time, valves 28 and 29 are closed while a valve 32 is maintained open. When the valve 32 is closed, and the water glass solution present in the injecting tubes are pressed into the ground or soil with the aid of a pump pumping water from the tank 27.

Then the valve 29 is closed, the valve 28 is opened and via a duct 30 acid solution is pumped from a tank 31 into the soil via the injecting tubes 25. The composition of the acid solution is as described in Example 6.

Under the effect of the acid solution the injected out or escaped water glass solution solidifies around each tube to an extent dependent on the quantity of injected material.

e.g. in a radius of approximately 30-50 cm around the tube and provides a suitably reliable, watertight base for the structures.

Claims (11)

Claims

1. A process for solidifying and rendering water-tight underground and other building structures, artefacts such as canals, basins, conduits and pipes, building elements, rocks and soils, which process comprises contacting an aqueous water glass solution and fluosilicic acid in the presence of a hydrogel-forming watersoluble organic polymer and a cross-linking agent at or in the vicinity of the object to be treated.

2. A process for solidifying and rendering water-tight underground and other building structures, artefacts such as canals, basins, conduits and pipes, building elements, rocks and soils by utilising an aqueous water glass solution and fluosilicic acid, characterised in that the water glass solution is brought into contact on, in or in the vicinity of, the object to be treated with the fluosilicic acid in the presence of 0.01-1 part by weight (calculated on one part by weight of solid matter in the water glass solution) of a hydrogelforming, water-soluble organic polymer and an agent promoting the cross-linking of the polymer.

3. A process as claimed in claim 2, wherein the amount of organic polymer is in the range of from 0.05 to 0.2 parts by weight calculated on the weight of solid matter in the water glass solution.

4. A process according to any one of claims 1 to 3, characterised in that the fluosilicic acid is used in the form of an aqueous solution.

5. A process according to any one of claims 1 to 4, characterised in that as the hydrogelforming, water-soluble organic polymer a polyelectrolyte, polymers or co-polymers of acrylic acid or methacrylic acid, partially hydrolysed polyacrylic acid esters or their alkali metal or ammonium salts, or a mixture of the said polyers are used.

6. A process as claimed in claim 5, wherein the po lyelectrolyte is carboxymethyl cellulose.

7. A process according to any one of claims 1 to 4, characterised in that as the hydrogelforming, water-soluble organic polymer a nonionic polymer is

8. A process as claimed in claim 7, wherein the non-ionic polymer is polyacryalmide and/or polyvinyl alcohol.

9. A process according to claim 5 or 6, characterised in that the gel-forming watersoluble organic polymer is dissolved in the aqueous solution of the water glass.

10. A process according to claim 7 or 8, characterised in that the gel-forming watersoluble organic polymer is dissolved in an aqueous solution of the fluosilicic acid.

1 A process according to claim 7 or 8, characterised in that the gel-forming watersoluble organic polymer is a polyacrylamide which is dissolved in the aqueous solution of the water glass and/or in an aqueous solution of the fluosilicic acid.

1 2. A process according to any one of claims 1 to 11, characterised in that as the cross-linking agent polyvalent metal compounds naturally occurring in ground water and/or contaminated aqueous solutions are used.

1 3. A process according to any preceding claim, characterised in that, at the site of the treatment there is applied in a preceding step a particulate solid material which does not impede the reaction, or such a material is added to one of the treatment solutions.

1 4. A process according to any preceding claim, characterised in that at the site of the treatment first a natural or synthetic rubber latex is applied, the latex is either allowed spontaneously to coagulate or is coagulated by means of an acid treatment; or natural or synthetic rubber is added to the water glass solution in an amount, calculated on one part by weight of solid material in the water glass solution, corresponding to 0.005-1 part by weight of solid matter.

1 5. A process as claimed in claim 14, characterised in that the amount of natural and/or synthetic rubber added is such that the solid matter content of the rubber is 0.05 to 0.2 parts by weight based on one part by weight of solid material in the water glass solution.

1 6. A process according to any preceding claim, characterised in that the treatment is repeated in any desired sequence and any desired number of times.

1 7. A process substantially as hereinbefore described in any one of Examples 1 to

11.