Background of the invention

[0001] The invention relates to a method for injecting a substance into soil and/or under a structure, the method comprising injecting a reacting substance, i.e. a substance which expands and hardens as a consequence of a chemical reaction, into the soil and/or under the structure along an injection bar.

[0002] The invention further relates to an apparatus for injecting a substance into soil and/or under a structure, the apparatus comprising means for injecting a reacting substance, i.e. a substance which expands and hardens as a consequence of a chemical reaction, into the soil and/or under the structure along an injection bar.

[0003] A wide variety of alternatives for injecting a substance into soil and/or under a structure have been disclosed. Publication US 6634831 discloses a solution, in which the soil is provided with a hole, into which a pipe is inserted. Through the pipe, a substance which expands as a consequence of a chemical reaction is injected into the soil. Publication US 2009/0155002 discloses a solution for improving soil and/or for lifting structures. According to the publication, the soil or structure is provided with a hole, and an injection bar having a fillable expansion element provided in connection therewith is arranged in the hole. A substance that expands as a consequence of a chemical reaction is injected into the expansion element. Still another solution for injecting a substance under a structure is disclosed in publication US 4567708. In this solution, earth-supported floors or slabs are lifted by injecting polyurethane foam under the floor or slab through a hole bored in the structure, the foam expanding and lifting the floor upwards. In all these cases, if more of a substance needs to be injected into soil or under a structure after the first injection, it is necessary to arrange a new pipe or injection bar, through which the sub- stance is injected, through the structure and/or in the soil. Floor lifting has also been performed with a technique, in which the old injection pipe is bored away, after which a new injection pipe or nozzle can be arranged in the same hole as the old injection point. Consequently, a great number of apparatuses and a lot of material are used up in re-injection. Aside from the floor-lifting technique, in which the pipe is bored away, it is very difficult to inject the substance into the same point as previously. Brief description of the invention

[0004] An object of the present invention is to provide a novel solution for injecting a substance into soil and/or under a structure.

[0005] The method of the invention is characterized by removing, after the injection has been finished, the reacting substance from inside the injection bar and then re-injecting the reacting substance by using the same injection bar.

[0006] The apparatus of the invention is characterized in that the apparatus comprises means for removing the reacting substance from inside the injection bar.

[0007] In the disclosed solution, a reacting substance is injected into soil and/or under a structure through an injection bar. After the injection, the reacting substance is removed from inside the injection bar. After this, the reacting substance is re-injected by using the same injection bar. Such a solution thus saves equipment and material, since the same injection bar can be used for a plurality of injections. Furthermore, the injection bar may be left substantially in its place, which allows re-injection substantially into the same point as the previous injection.

[0008] An idea of an embodiment is that the injected reacting sub- stance is removed from inside the injection bar by filling the injection bar with a non-reacting substance after the injection. Such a solution is reasonably simple and reliable. If desired, this substance may also be used for cooling the walls of the injection bar in between the injections of the reacting substance.

Brief description of figures

[0009] The invention will be described in greater detail in the attached drawings, in which

Figure 1 schematically shows injection of a substance into the soil and/or under a structure,

Figure 2 schematically shows how an injection bar is emptied of in- jected reacting substance, and

Figure 3 schematically shows re-injection by using the same injection bar that was already used for injecting the reacting substance earlier.

[0010] In the figures, some embodiments of the invention are shown simplified for the sake of clarity. Similar parts are marked with the same refer- ence numbers in the figures. Detailed description of the invention

[0011] Figure 1 shows an injection apparatus 1 for injecting a reacting substance 3 into soil 4 along an injection bar 2. The reacting substance 3 is a substance that expands as a consequence of a chemical reaction and con- denses, fills or replaces the surrounding soil or lifts and balances structures. The reacting substance 3 also hardens after the injection. In this description, the term 'reacting substance' refers to a substance that expands and hardens as a consequence of a chemical reaction.

[0012] The outer diameter of the injection bar 2 may vary between 3 and 200 mm, for example. The length of the injection bar may vary between 0.5 and 25 m, for example. The injection bar 2 may be made of metal, such as steel. The injection bar 2 may also be made of some other material, such as plastic, e.g. polyethylene PE. Also, the injection bar 2 need not necessarily be rigid. The injection bar 2 may thus be a plastic hose or pipe, for example. Fur- thermore, if the injection bar 2 is a hose, its wall may be provided with textile reinforcement fabrics or metal or other similar reinforcements.

[0013] In Figure 1 , reference numeral 5 designates means for feeding the reacting substance 3 into the injection bar 2. In this case a valve 6 is opened and a valve 8 closed. The means 5 may comprise a mixing chamber 10 and a first channel 1 1 for feeding a first component into the mixing chamber 10 and a second channel 12 for feeding a second component into the mixing chamber 10.

[0014] The reacting substance may be a substance that expands as a consequence of a chemical reaction, such as a polymer, an expansive resin, or an organically incrystallizable, chemically expansive multicomponent substance.

[0015] The reacting substance may be, for example, a mixture mainly consisting of two components. In such a case, the first component may mainly contain polyether polyol and/or polyester polyol, for example. The sec- ond component may contain isocyanate, for instance. The volumetric ratios of the first component to the second component may vary between 0.8 to 1 .2 : 0.8 to 1 .8, for example. The reacting substance 3 may further contain catalysts and water and, if desired, also other components, such as silica, rock dust, fibre reinforcements, and other possible additional and/or auxiliary agents. [0016] The injectable substance is preferably such that it starts reacting by expanding within 0.5 to 3600 seconds after being injected into the soil 4. In an embodiment, the substance starts reacting within 20 or more than 25 seconds after being injected. In still another embodiment, the substance starts reacting within less than 50 seconds after being injected.

[0017] The substance expands to a volume that is e.g. 1 .1 to 120 times the original volume. In other words, the expansion coefficient of the substance, i.e. the volume of the substance at the end of the reaction as compared with the volume of the substance at the beginning of the reaction, may be of the order of 1 .1 to 120, for instance. Preferably, the substance is arranged to expand to a volume that is 1 .5 to 20 times the original volume.

[0018] Figure 2 shows a situation where the feeding of the reacting substance 3 into the soil has been finished. At this stage, the valve 6 is closed. Reference numeral 7 designates a container and means for feeding into the injection bar 2 a substance that keeps the injection bar open. Thus, this is carried out with the container and means marked with reference numeral 7, when the valve 8 is open and a non-reacting substance 9 is fed into the injection bar 2. The non-reacting substance 9 pushes the reacting substance 3 away from the injection bar 2. The non-reacting substance is a substance that does not substantially expand, solidify or harden.

[0019] Preferably, the amount of non-reacting substance 9 fed into the injection bar 2 exceeds the internal volume of the injection bar 2. For instance, if the internal volume of the injection bar 2 is 1 .0 I, the non-reacting substance is fed in an amount of 1 .5 I, for example. This ensures that the en- tire injection bar 2 down to its very end is emptied of the reacting substance 3. Furthermore, by feeding non-reacting substance 3 into the injection bar 2 in an amount that is larger than the internal volume of the injection bar, it is possible to provide an injection space 13 inside the already injected reacting substance 3 after the bottom end of the injection bar 2, as illustrated in Figure 2. Then, in re-injection, the reacting substance 3 can be injected reliably out of the injection bar 2 and made to spread inside the already reacted substance. When the injectable substance is a substance that expands as a consequence of a chemical reaction, it is possible to inject more of a substance inside the injectable substance, and when this substance expands, it breaks the structure of the already reacted substance and condenses in connection with the already reacted substance. [0020] The reacting substance must be removed from the injection bar 2 before it hardens and is substantially attached to the walls of the injection bar 2. Typically, two-component substances, for example, start hardening as soon as the different components are mixed with each other. At the beginning of hardening it is still possible to remove the reacting substance from inside the injection bar 2, but after the gel time of the reacting substance 3 has ended, it has been attached too firmly and tightly to the injection bar 2, which makes it very arduous and difficult to remove it from inside the injection bar 2.

[0021] The non-reacting substance may be easily removed from in- side the injection bar, after which the injection of the reacting substance may be continued. This is illustrated in Figure 3. In Figure 3, the valve 8 is closed and the valve 6 open, and the reacting substance 3 is fed along the injection bar 2 from the container by using the means 5.

[0022] The non-reacting substance may be, for instance, castor oil or some other non-reacting substance suitable for the purpose, such as water. More preferably, however, the non-reacting substance is such that its viscosity is higher than that of water, and so the non-reacting substance pushes the reacting substance 3 efficiently out of the injection bar 2. Further examples of non-reacting substances include polyester polyol and polyether polyol per se. Thus, the above solution may also be implemented in such a manner that it is not necessary to use the container and means marked with reference numeral 7 at all. Hence, when the reacting substance 3 is fed along the injection bar 2, both the first component from the first channel 1 1 and the second component from the second channel 12 are fed into the mixing chamber 10, whereupon they are mixed in the mixing chamber 10 and form the reacting substance 3 together. The non-reacting substance 9, for its part, is fed into the injection bar 2 so that only one component, which alone is a non-reacting substance 9, is fed into the mixing chamber 10.

[0023] The non-reacting substance 9 may be removed from the in- jection bar 2 before the reacting substance is re-injected by, for example, sucking the injection bar 2 empty. On the other hand, the non-reacting substance 9 may also be left inside the injection bar, in which case the reacting substance 3 pushes the non-reacting substance 9 into the soil at the beginning of the injection.

[0024] The reacting substance may be such that, upon reacting, it becomes warm and thus heats e.g. the injection bar 2. For example, the two- component substance is typically a substance that generates heat when it reacts. The temperature of the non-reacting substance may be adapted so as to cool down the injection bar 2. Thus, when the injection bar is opened, it is possible to cool down the injection bar 2, if desired.

[0025] After the reacting substance has been injected, the injection bar 2 may also be emptied in some other way than by filling it with non-reacting substance 9. The injection bar 2 may be emptied by, for instance, blowing the injection bar 2 empty by means of pressurized air, for example.

[0026] In addition to the above-described injection directly into the soil, the disclosed solution may also be applied to techniques in which around the injection bar and/or at the end thereof there is arranged an expansion element, inside which the reacting substance 3 is injected by means of the injection bar 2. The injection bar 2 may further be used for injecting the reacting substance 3 under a slab or floor or some other structure, which means that the reacting substance is not necessarily injected into the soil.

[0027] In some cases, the features described in this application may be used as such, regardless of other features. On the other hand, the features described in this application may also be combined to provide various combinations as necessary.

[0028] The drawings and the related description are only intended to illustrate the idea of the invention. The invention may vary in its details within the scope of the claims.