WO2000061917A1

WO2000061917A1 - Method and device for the injection of hardenable compounds in cavities

Info

Publication number: WO2000061917A1
Application number: PCT/SE2000/000436
Authority: WO
Inventors: Bengt Arvidsson
Original assignee: Bengt Arvidsson
Priority date: 1999-03-30
Filing date: 2000-03-06
Publication date: 2000-10-19
Also published as: AU4154400A; SE9901153L; SE512113C2; SE9901153D0

Abstract

An injection device comprises an injection pipe (1) having front and rear ends (2, 3). There is an elastic, expandable ring (6) on the outside of the pipe (1) for fixing and sealing the same in a bore hole. At a point at a distance from the rear end (3) of the injection pipe, a branch pipe (13) is connected which may be connected to a hose (12) for supplying mortar or water to the interior of the injection pipe. In a rear gable piece (16), a piston (18) being movable to and fro is arranged which may be connected to an external percussion mechanism with the purpose of setting the mortar or the compound inside the injection pipe in vibration. During injection, the mortar is fed into the bore hole under low pressure.

Description

METHOD AND DEVICE FOR THE INJECTION OF HARDENABLE COMPOUNDS IN CAVITIES

Technical Field of the Invention In a first aspect, the present invention relates to a method for the injection of hardenable compounds in cavities by means of an injection pipe having front and rear ends and an inlet mouth through which a flowing compound from outside is fed into the interior of the pipe, as well as an outlet mouth positioned in the front end of the pipe through which mouth the compound is further fed into the cavity to be injected, the injection pipe being fixed and sealed in the cavity by means of an elastic, expandable ring on the outside of the pipe.

Background of the Invention

In the construction industry, injection is used for different types of sealing and reinforcing purposes. Rock, for instance, is injected, in particular rock surrounding tunnels, with the purpose of reinforcing the surface layer mechanically, as well as inhibiting water leakage therethrough. In a similar way, masses of earth are injected with the purpose of stabilizing the earth and bringing about a surface layer with an improved density. During the injection, a number of spaced cavities are drilled which are filled with a hardenable mass, which initially is liquid and which has the ability to solidify when the cavity has_., been filled. For the injection of rock, a simple cement mortar, i.e. a mixture of water and finely pulverized cement, possibly in combination with suitable addi- tives, is commonly used as a compound. The reason for using finely pulverized cement without coarse-grained ballast material is that it is desirable that the mortar should penetrate into and fill also finer channels, such as cracks, pores and the like, adjacent to the individual bore hole with the ulti- mate purpose of bringing about a liquid-sealed and strong structure in the surface layer closest the rock wall.

In previously known techniques, the cement mortar has been pressed into the drilled cavity via the injection pipe with a high pressure (10-20 kg/cm²) for the purpose of bringing about an optimum penetration of the mortar also in the fine channels or cracks adjacent to the cavity. However, investigations, on which the present invention is based, have shown that the use of high pressures in connection with the injec- tion of the mortar or the compound is inappropriate. Thus, there is a marked tendency that the mortar during influence of the high pressure is dewatered in a way which counteracts penetration of the cement particles in the very finest channels of the rock structure. In order to better understand this dewatering phenomenon, the intellectual experiment may be made that the mixed compound of water and the fine, solid cement particles is introduced a sack with porous, permeable walls, and then the compound is pressurized. Since the water is of low viscosity and follows the law of least resistance, the water will primarily pass the pores in the wall of the sack, while the majority of the solid particles remain in the sack without accompanying the water. The cement compound conducts in the same way when the same is injected with a high pressure into drilled rooms in rock or soil. The thick bore hole is filled up in a fast and simple way by the cement compound, but when the compound then is to pass out in the finer channels adjacent to the hole, the compound is dewatered so that primarily only the water penetrates into the channels. It is true that also the solid cement particles will partly penetrate into the channels, but the longer and finer these are, the more marked the tendency will be that the channel portions positioned innermost and furthest away from the bore hole are filled with or are passed by water, while the cement particles are stopped closer to the bore hole room. The result of a mediocre filling ratio in the finest channels of the rock structure will, of course, be a structure with moderate density and strength.

Objects and Features of the Invention The present invention aims at obviating the above- mentioned shortcoming of previously known injection technique. Therefore, a primary object of the invention is to provide an injection method which can give a considerable improved den^¬ sity in such rock or earth structures which include fine as well as long channels in the form of cracks, pores and the like.

According to the invention, the above-mentioned objects are attained by the features defined in the character- izing clause of claim 1. A preferred embodiment of the method according to the invention is defined in the dependent claim 2.

In a second aspect, the invention also relates to a device by means of which the method may be carried out in a simple way. The features of this device are defined in claim 3. An advantageous embodiment of the device according to the invention is furthermore defined in the dependent claim 4.

Brief Description of the Appended Drawings In the drawings:

Fig 1 is a longitudinal section through an injection device according to the invention, Fig 2 is a partial longitudinal section through an alternative embodiment of the device, an expandable ring being shown in a starting position,

Fig 3 is an analogous longitudinal section showing the same ring in an expanded, fixing state, Fig 4 is a section showing the device according to fig 1 in a state immediately before the insertion in a drilled hole,

Fig 5 is a section showing the same device inserted in the bore hole, mortar being injected therein, and Fig 6 is a section showing the bore hole after finalized injection.

Detailed Description of Preferred Embodiments of the Invention

The device shown in fig 1 includes an injection pipe, in its entirety designated 1, which has a front end 2 and a rear end 3. The inside of the pipe 4 opens at the front end 2 in a mouth 5 through which cement mortar or other injection compound may be fed out of the pipe. Thus, the mouth 5 forms an outlet for the mortar.

In the area of the front end of the injection pipe, an elastic and expandable ring 6, e.g. of rubber, is arranged. This rubber ring is arranged outside a cone-shapedly tapering sleeve 7 which is connected to a cuff 8, which in turn is rigidly connected to a nut 9, the interior thread of which is in engagement with an external thread 10 on the injection pipe. By means of the nut, the cuff and the sleeve may be displaced axially along the injection pipe, the conicity of the sleeve 7 being used to expand the rubber ring 6. Expansion of the rubber ring 6 has the double function of fixing the injection pipe in the desired cavity as well as sealing the ring-shaped passage between outside of the injection pipe and the inside of the cavity.

In fig 2 and 3 an alternative embodiment is shown, according to which a rubber ring 6' is arranged directly outside the injection pipe 1, more precisely between an axially movable cuff 8' and a fixed adjusting ring 11. When the cuff 8' is distanced from the adjusting ring 11, as is shown in fig 2, the rubber ring 6' has a minimal outer diameter. When the cuff by means of the screwable nut 9 is displaced axially in the direction towards the adjusting ring, as is shown in fig 3, the rubber ring 6¹ is compressed in the axial direction, the outer diameter increasing. In that manner, the ring 6' may fix and seal the injection pipe in the current cavity.

In fig 1 is shown how a hose 12 is connected to the injection device. Through this hose, the mortar or the com- pound may be supplied from an external source (not shown) , which includes a pump suitable for the purpose.

As far as the device according to the invention has been described hitherto, the same is in all essentials previously known. However, in previously known injection devices, the supply hose or conduit 12 has been connected to the rear end of the injection pipe 1 in the axial extension thereof. In addition, the cement mortar has been supplied under high pressure, (10-20 kg/cm²) .

Characteristic for the device according to the inven- tion is that a branch pipe 13 is connected to the injection pipe 1, more precisely at a point at a certain distance from the rear end 3 of the injection pipe. At a free end, distanced from the injection pipe, this branch pipe 13 has an inlet mouth designated 14. In practice, this mouth is housed in a schematically shown coupling 15 for connecting the pipe 12 to the branch pipe. In the coupling 15 or in the vicinity thereof, there may advantageously also be a cut-off valve (not shown) . In the area of the rear end of the pipe 1, there is an gable wall or a gable piece 16 with a through bore 17, suitably situated centrally. A body 18 being movable to and fro is arranged in this bore. This body has a long narrow shape and the character of a piston, which, for instance, may consist of a cylindric bar or rod. A first end 18' of this piston is situated inside the gable piece 16, while an opposite end 18" is situated outside the gable piece 16. The. end portion 18" positioned outside the gable piece may be connected to a percussion mechanism (not shown), e.g. a conventional poker vibrator. At 19, 20, two stopping members are shown schematically which have the purpose of preventing the piston from falling out of the appurtenant bore. By means of the percussion mechanism, the piston may be set in fast, intermittent motions which apply impact motions to the mortar positioned in the interior of the injection pipe which impact motions set the mortar in vibration. Advantageously, the front end portion 18' of the piston 18 is located approximately at the point of intersection between the oblique branch pipe 13 and the injection pipe 1. Although the angle of the branch pipe 13 in relation to the injection pipe may vary most considerably, the same should in practice be within the range of 30-60°, the branch .pipe extending obliquely outwards/backwards from the injection pipe.

A venting valve 21 which normally is closed, but which, if required, may be opened so as to vent the interior of the injection pipe, may be arranged in the cylinder wall of the injection pipe 1.

Reference is now made to figs 4-6, which illustrate the method according to the invention. In fig 4 is shown how a cavity 22 is present in a rock wall 23, which in this example is assumed to extend vertically. The cavity 22 has been brought about by drilling, and therefore the same has a cylindric basic shape. A crack, which is shown on an exaggeratedly large scale, is designated 24. In practice, there are a plurality of different, small cracks or pores in rocks with a comparatively loose structure, which communicate mutually as well as with the cavity 22. The purpose of the injection is to reinforce the surface layer of the rock wall by, as far as possible, filling out those cracks, pores or other fine channels which are present in the surface layer of the rock adjacent to the wall 23. The depth of this surface layer may be within the range of 0,5-1 m.

In fig 4 the device according to fig 1 is shown in an empty state outside the cavity 22, a schematically illustrated percussion mechanism 25 being shown connected to the vibrator piston 18.

In fig 5 the device is shown with the front end portion of the injection pipe 1 inserted in the cavity 22. In a first step after insertion, the rubber ring 6 is brought to expand until the same is forcefully pressed against the inside of the cavity 22. In this way, the injection pipe is fixed in the cavity at the same time as the ring-shaped passage between the outside of the pipe and the inside of the cavity is sealed. In the next step, cement mortar 26 is introduced to the interior of the injection pipe via the supply hose 12 and the branch pipe 13. According to the invention, the mortar should be fed in under low pressure, e.g. within the range of 2-8, suitably 3-5 kg/cm². At the same time as the mortar is inserted in the injection pipe,- the percussion mechanism 25 is activated, which sets the piston 18 in motion to and fro, more precisely in intermittent, fast motions. This results in the fact that the cement mortar arriving to the interior of the injection pipe is submitted to axially directed impact motions, which propagate axially in the cement mortar string contained in the injection pipe and the cavity 22, respectively, and therefrom further out into the finer channels 24 in the rock adjacent to the cavity 22. By the fact that the cement mortar is introduced to the cavity under a low pres- sure, the risk of dewatering the mortar, which is typical for mortar that is exerted to high pressure, is obviated. The consequence of this is that the mortar preserves the homogeneity thereof also into the finer channels in the rock, which communicates with the cavity. In doing so, the vibrations which are applied to the mortar have proved to entail that the solid particles of the mortar penetrates into the channels in an effective way. The network of intercommunicating, fine channels in the shape of cracks and pores which are included in the rock is, therefore, in the main filled out completely while achieving high strength and density in the surface layer of the rock surrounding the individual, injected cavity.

In order to make the injection even more effective, it is, according to the invention, also feasible to use the device according to the invention for rinsing the fine channels of the rock before injection. In such rinsing, the injection pipe 1 is fixed and sealed in the same way as has been described above, but instead of cement mortar, water is fed into the same and further out in the cavity together with the complicated network of fine channels which communicate with the cavity. Tests have shown that rinsing during 10 to 20 minutes is sufficient to effectively eliminate loose particles from the channel system inside the rock. After performed rinsing, drying may take place during a suitable time. In fig 6 is shown how the injected cavity may be sealed by means of a plug 27, e.g. consisting of wood or rubber, when the cement mortar has begun to solidify and the injection pipe has been removed out of the cavity.

Instead of cement mortar, it is also possible to use other compounds that may be hardened and solidified after initially having had a liquid form. When injecting rock a pure cement mortar is, however, preferred with most finely ground cement particles. The invention may also be applied_^ for the injection of masses of earth or constructions of brick, con- crete and the like, other injection compounds possibly being appropriate.

Claims

1. Method for the injection of hardenable compounds in cavities (22) by means of an injection pipe (1) having front and rear ends (2, 3), and an inlet mouth (14) through which compound in a flowing form from outside is fed into the interior of the pipe, as well as an outlet mouth (5) positioned in the front end (2) of the pipe through which the compound is further fed into the cavity (22) to be injected, the pipe (1) being fixed and sealed in the cavity by means of an elastic, expandable ring (6) on the outside of the pipe, c h a r- a c t e r i z e d in that the flowing compound (26) is introduced under low pressure to the interior of the injection pipe (1) via a branch pipe (13) which is connected to the injection pipe at a point at a distance from the rear end (3) of the injection pipe, and submitted to intermittent impact motions directed axially in relation to the injection pipe, which impact motions set the same in vibration.

2. Method according to claim 1, c h a r a c t e r i z e d in that the individual cavity (22) together with the finer channels (24) communicating therewith, such as cracks, pores and the like, in a step before the injection is rinsed with water which is introduced into the cavity via said injection pipe (1) and branch pipe (13) , and which - in analogy with the hardenable compound - is submitted to intermittent impact motions directed axial-ly in relation to the injection pipe, which impact motions set the water in vibration.

3. Device for the injection of hardenable compounds in cavities, including an injection pipe (1) having front and rear ends (2, 3), and an inlet mouth (14) in order to supply a compound from the outside in a flowing form to the interior of the injection pipe, as well as an outlet mouth (5) positioned in the front end (2) of the injection pipe in order to feed the compound further into the cavity (22) to be injected, the injection pipe having, on the outside thereof, at least one elastic, expandable ring (6, 6') for fixing and sealing the same in the cavity, c h a r a c t e r i z e d in that the inlet mouth (14) is included in a branch pipe (13) which is connected to the injection pipe at a point at a distance from the rear end (3) thereof, and that a bore (17) is recessed in a rear gable piece (16) of the injection pipe for a body (18) being movable to and fro in relation to the gable piece, which body has the purpose of applying to the compound positioned inside the injection pipe intermittent impact motions directed axially in relation to the injection pipe, which motions set the compound in vibration.

4. Device according to claim 3, c h a r a c t e r i z e d in that said body consists of a long narrow piston (18) which has a first end portion (18') situated inside the gable piece (16) and a second end portion (18") situated outside the gable piece so as to connect to a percussion mechanism (25).