WO2000068544A1

WO2000068544A1 - Device and method in connection with a rock wall

Info

Publication number: WO2000068544A1
Application number: PCT/SE2000/000191
Authority: WO
Inventors: Håkan ERIKSSON
Original assignee: Gurlita Maskin Aktiebolag
Priority date: 1999-04-21
Filing date: 2000-02-01
Publication date: 2000-11-16
Also published as: SE9901414L; SE9901414D0; AU2838100A; SE514084C2

Abstract

Device and method for reinforcement and sealing a rock wall, which device comprises a reinforcement bar (1) adapted to be introduced into a bore hole (30) in the rock wall, into which bore hole a filling material (31) is intended to be injected, and also comprises a non-return valve (4) for the filling material. The device further comprises a tubular shaped expander (20) for anchoring the device in the rock wall, which expander, before the expansion, exhibits at least one, preferably at least two, axially extending indentations (22), whereby the expander has a peripherical length in its cross-section which exceeds the circumference of the bore hole (30), but has a largest diameter which is less than the diameter of the bore hole, said expander (20) being arranged to be expanded and thereby plastically deformed essentially without its peripherical length increasing, at anchoring of the device in the rock wall.

Description

DEVICE AND METHOD IN CONNECTION WITH A ROCK WALL

TECHNICAL FIELD

The invention relates to a device and method for reinforcement and sealing of a rock wall, which device comprises a reinforcement rod, e.g. a conventional reinforcement bar adapted to be introduced into a bore hole in the rock wall, into which bore hole a filling material thereafter is injected. The device is of the type comprising a non-return valve for the filling material. The invention is utilised in the construction of tunnels and other rock cavities.

PRIOR ART

On working in rock walls, e.g. for constructing tunnels or rock cavities, reinforcement of the rock wall is most often required to increase the strength, and sealing of cracks and the like to prevent damp and water from penetrating the tunnel or cavity. Known methods of reinforcement consist in providing the rock wall with evenly dispersed bore holes, which can have a diameter of about half a decimetre and a depth of about 1-6 metres.

One method of reinforcing rock walls has been and continues to be the insertion into the bore holes of two concentrically arranged tubes of different diameter. The space between the walls of the tubes is filled with cement or concrete, following which the tubes are taken out before the filling material has hardened and a reinforcement bar can be stuck into the central hole. A major disadvantage of this method is that the filling material and reinforcement bar fall out of the hole again relatively frequently, for which reason the reinforcement often has to be repeated several times before it succeeds. If in addition water leaks out of the rock into cracks which lead into the bore hole, the filling material can be washed away before it manages to harden. In this case, the rock must instead be sealed in a first stage, a rubber plug or tap normally being arranged in the bore hole opening and the hole being filled with concrete or cement which is then allowed to solidify. Following this, a hole is drilled in the concrete/cement which is reinforced in the same way as described above. As is clear, the method comprises several stages and it is nevertheless not entirely certain that the reinforcement remains in place.

In a more modern known system, a long bolt is introduced into each bore hole, which bolt is provided at the top with an expander for anchoring in the bore hole. Arranged in the end of the bolt which extends out of the bore hole is a washer which lies like a cover over the bore hole and in the centre of which a hemisphere is arranged. The bolt extends a distance out of the hemisphere and is surrounded there by a nut which is tightened when the expander in the bolt top is to be anchored in the rock. Following anchoring, cement paste is injected into the hemisphere to proceed inwards into the bore hole, first inside a plastic tube which surrounds the bolt, and then outside this plastic tube until the cement paste emerges through a hole in the washer. This system certainly provides reinforcement of the rock wall, but no appreciable sealing of water-bearing cracks and the like. Problems of corrosion at the bolt can also occur if air bubbles are formed in the cement closest to this.

In SE 9701325-4 there is described another type of rock bolt device, which comprises a non-return valve for the filling material. This device consists of two separate parts, a first part being a sleeve shaped device provided with a sealing cuff in one end thereof (the inner end) and the other end consisting of the rock bolt itself, i.e. in principle a reinforcement bar. At the application of the device in a bore hole in the rock wall, the first part is first introduced a short distance into the bore hole and is brought to remain there by aid of a sealing member. Thereafter, the reinforcement bar is introduced through the sleeve shaped device and through the sealing cuff, a gap being formed between the reinforcement bar and the walls of the sleeve shaped device, through which gap a filling material, such as cement grout, can be injected. The sealing cuff is thereby acting as a non-return valve in co-operation with the reinforcement bar. A device of the type shown in SE 9701325-4 does indeed constitute development progress, but nevertheless it exhibits some drawbacks, e.g. that it takes several operational steps at the application of the device, since it consist of two separate parts. Another problem is that the reinforcement bar cannot be provided with an anchoring device in the end thereof which is intended to be positioned in the rear end of the bore hole. Such an anchoring device could, due to space reasons, not be introduced trough the sleeve shaped device and the sealing cuff.

In SE 9801476-4 there is described yet another rock bolt device, which exhibits some similarities with the one described in SE 9701325-4. However, the rock bolt device of

SE 9801476-4 exhibits the advantage that the sleeve shaped device, including the nonreturn valve, is permanently connected to the reinforcement bar, already before the rock bolt device is introduced into the bore hole in the rock wall. Thereby, there is also provided the possibility to equip the reinforcement bar with an anchoring device in its inner end. Such an anchoring device or expander will enable extra securing of the rock bolt device in the bore hole. However, it has been found that the anchoring device shown in SE 9801476-4 works best in relatively leakproof and stabile rock walls, while it will give a poorer anchoring in less leakproof and more unstable or porous rock walls.

SE 7902129- ldecribes yet another type of rock bolt device, which consists of a tubular shaped bolt which has been deformed by being provided with a longitudinal indentation. The deformed, tubular shaped bolt is sealed in the ends thereof, it being connected to a source of pressurised liquid in one end thereof at the application of the bolt in the rock wall. The bolt expands by the pressure, so that is brought to bear against the walls of the bore hole. By use of the device shown in SE 7902129-1 there is only achieved reinfor- cement of the rock wall, but not any sealing worth mentioning. Moreover, the bolt is not protected against corrosion, which means that it has a limited life.

Conventional methods of sealing the rock wall comprise e.g. labour-intensive and expensive so-called "lining" of the rock wall, i.e. cladding with concrete. Another known method utilises a sealing material which is injected into the rock wall. This has been found to lead to very great environmental disadvantages, as the sealing material contains the toxic substance acrylamide, which can be dispersed in the groundwater.

BRIEF ACCOUNT OF THE INVENTION The aim of the present invention is to offer a device for reinforcing and sealing a rock wall, by means of which device the aforementioned disadvantages are avoided or at least minimised, it being possible to carry out reinforcement and sealing of the rock wall in just a few stages, meaning that the reinforcement remains securely in place at the same time as sealing of water-bearing cracks leading into the bore holes is achieved and air bubbles in the cement are avoided. The invention especially aims at providing such a device which is especially adapted to, by means of an anchoring device, be anchored in relatively leaky, unstable or porous rock walls.

This is achieved by means of a device for reinforcing and sealing a rock wall according to claim 1.

Thus, the device according to the invention comprises a reinforcement rod, e.g. a conventional reinforcement bar intended to be introduced into a bore hole in the rock wall, into which bore hole a filling material is then injected, said device also comprising a non-return valve for the filling material. The non-return valve and the reinforcement bar are preferably, but not necessarily, permanently connected to each other already before the device is introduced into the bore hole. The device according to the invention further comprises a tubular shaped expander for anchoring of the device in the rock wall, which expander, before expansion, exhibits at least one, preferably at least two, axially extending indentations, whereby the expander has a periphery length in its cross section, which exceeds the circumference of the bore hole, but a largest diameter which is less than the diameter of the bore hole, said expander being arranged to expand when the device is being anchored in the rock wall, and thereby to be plastically deformed essentially without its peripherical length increasing.

According to one aspect of the invention, the expander exhibits at least three, preferably at least four and most preferred four axially extending indentations, which are preferably arranged at essentially equal interval about the circumference of the expander. The bulgings of the expander, which are situated between said indentations, are softly curved, and in the part thereof which is situated most distant from the centre line of the expander they essentially take the shape of half a circular cylinder. The expander and thereby the device is arranged to be anchored in the bore hole when the expander is connected to an external source of pressurised liquid.

The non-return valve is adapted to withstand a positive pressure of the filling material in the bore hole. The filling material is thus injected under positive pressure, at which any cracks in the rock leading into the bore hole are sealed. Said non-return valve preferably consists of a rubber sleeve which encloses an injection tube provided with outlet openings, which injection tube is preferably joined to said reinforcement bar or equivalent.

Further features and aspects of the invention are evident from the following claims and the detailed description of the invention.

BRIEF DESCRIPTION OF DRAWINGS

Reference will be made in the detailed description of the invention to the enclosed drawings, of which

Fig. 1 represents a lateral view, partly in cross-section, of the part of the device which is positioned adjacent to the opening of the bore hole and which contains the nonreturn valve. Fig. 2 represents a lateral view, partly in cross-section, of the part of the device which is positioned furthest in in the bore hole and which contains an expander according to the invention, for anchoring in the rock.

Fig. 3 a represents a cross-sectional view of the expander in Fig. 2, before it is pressurised for anchoring in the bore hole.

Fig. 3b represents an upper end of the expander in Fig. 2 and 3a, as seen from above.

Fig. 4 represents a lateral view, partly in cross-section, of the bore hole and the reinforcement during the hardening phase of the filling material.

Fig. 5 represents a lateral view, partly in cross-section, of the finished reinforcement in the rock.

DETAILED DESCRIPTION OF THE INVENTION

With reference first to Fig. 1, a reinforcement bar which forms part of the device is denoted by the number 1. For drawing technical reasons the reinforcement bar in the figure is cut away at the top but in reality has a length of about 0.5-10 m, preferably 1-7 m and even more preferred 2-5 m. In Fig. 1 and 2 the device is shown as it is arranged in a vertical, upwardly directed bore hole in the roof of the tunnel or rock cavity, which position is used in the further description. However, it is to be understood that the device can just as well be used in a horizontal hole, an angled hole or in a vertical, downwardly directed hole. The reinforcement bar 1 has a strongly profiled surface for fastening securely in the cement or concrete, henceforth termed filhng material, which will enclose the same. Joined as an extension of the reinforcement bar arranged at the bottom, via a coupling sleeve 2 welded firmly at both ends, is an injection tube 3 which accordingly has an inner longitudinal cavity and is open at the bottom for the connection of hosing for filling with the filling material.

Arranged a distance below the coupling sleeve for the reinforcement bar 1 and the injection tube 3 is a non-return valve 4. This non-return valve 4 is adapted to withstand a positive pressure of the filling material when this is injected under positive pressure into the bore hole via the non-return valve. Thanks to this non-return valve, the filling material does not run out of the bore hole before it solidifies, in spite of the positive pressure. The non-return valve 4 preferably comprises a rubber sleeve 5 which encloses a part of the injection tube 3. In the area of the rubber sleeve the injection tube has a number of outlet openings 6 for the filling material. The rubber sleeve, which can of course also be manufactured from another, to some extent elastic, strong material, is suitably formed as the envelope of a truncated cone, having a first diameter at the bottom end and a second, smaller diameter at the top end. At the first diameter, the rubber sleeve 5 is vulcanised firmly at an internally threaded eye nut 7, which in turn is screwed firmly on an externally threaded ring fastener 8. The ring fastener 8 encloses the injection tube 3 and is welded firmly to the same. The ring fastener 8 also has a flange 9 at the bottom, on the upper surface of which flange the eye nut 7 rests. The upper, smaller diameter of the rubber sleeve 5 is adapted to end sealingly around the injection tube 3. For this purpose the nose is suitably provided with a few, e.g. two, internal lip seals consisting of O-rings which are set into the rubber sleeve, or by a few continuous projections on the inside of the rubber sleeve in the tip part.

Below the flange 9, the injection tube is enclosed by a narrow tube 13 with an upper flange 14 which abuts against the lower surface of the flange 9. Resting against the lower surface of the flange 14 is the upper short end of a seal in the form of a sleeve 10 which suitably also consists of rubber. This rubber sleeve 10 encloses a part of the lower section of the injection tube surrounded by the narrow tube 13, its lower short end resting against a washer 11 which in turn rests against a nut 12. In the area of the nut 12 and a distance up under the rubber sleeve 10 the injection tube 3 and/or the narrow tube

13 are threaded externally with the same thread size as the nut 12.

Arranged in the upper part of the device, suitably at its top, is a top piece forming an expander 20 arranged, suitably welded to the reinforcement bar 1. The expander is shown in Fig. 2, which forms a continuation of the device shown in Fig. 1, a longer piece of the reinforcement bar 1 (only partly shown) connecting the part according to Fig. 1 to the part according to Fig. 2. In the lower end the expander exhibits a lid 21 and a stiffening sleeve 27, and in the upper end it exhibits a lid 25 and a stiffening sleeve 28. Running to the expander 20 and through the lid 21 there is a thin pipe 26, preferably of the type of a hydraulic pipe, adapted to pressurise the expander.

The expander 20, which consists of a tube, is shown in Fig. 3 a and in a view from above in Fig. 3b. In the shown preferred embodiment, the tube exhibits four axially extending indentations 22, which results in four intermediate bulgings 23. The bulgings have a softly curved shape and at least between the two points x and y, they take the shape of a circular arc with a centre angle of about 180°. Considering the extension of the bulgings 23 out of the plane of the figure, the part between two imagined axial lines which extend through the points x and y essentially take the shape of half a circular cylinder. Also the indentations 22 have a softly curved shape and typically exhibit a radius which is less than the radius of the bulgings 23. The indentations 22 preferably extend, in the non- expanded state of the expander, as far in towards the centre line of the expander that their walls will abut each other, i.e. the walls of each indentation 22 abut the walls of the nearest lying indentations. It can also be conceived that the walls merely lie almost against each other. The walls 23 of the bulgings however, do preferably not abut each other, i.e. they are arranged at intervals of preferably equal distance. At one of the bulgings 23 of the expander there is shown the inlet 24 for connection to a source of pressurised liquid, via the hydraulic pipe 26. The tube with the indentations 22 and bulgings 23 is ended with stiffening sleeves 27, 28 and welded lids 21, 25 in each end, the inlet 24 passing through the lid 21.

The expander 20 typically has a length of about 0.3 - 3 metres, preferably 0.5 - 2 metres, a diameter of 30 - 60 mm, preferably 35 - 50 mm, for an imagined circle which circumscribes the deformed tube in the non-expanded state, and a wall thickness of about 1 - 4 mm, preferably 1.5 - 3 mm.

The described details are preferably, where other is not indicated, manufactured from so called cam steel which may be hot zinc coated or surface protected in some other way.

The function of the device is as follows. A hole 30, Fig. 4, is bored into the rock wall, of at least the same length as the length of the device. The device is introduced into the bore hole so far that the washer 11 and nut 12 will be located at the mouth of the bore hole. After this, the expander 20 is pressurised via the hydraulic pipe 26, which runs along the device and suitably in a groove in the sleeve 10, by a pressure of about 100 - 500 bar, preferably 200 - 300 bar, whereby the bulgings of the expander will bend out to bear against the bore hole 30. Thereby, the two walls 22a, 22b in each bulging 22 will be move in a direction from each other, and out from the centre line of the expander, so that the bulgings can be expanded. Next to each other lying walls in to next to each other lying bulgings will on the contrary move towards each other, preferably however with a remaining gap left between them. The walls of the expander are however not stretched, which lessens the risk of fissure formation. The peripherical length of the walls will hereby be the same as before the expansion, the peripherical length of the walls exceeding the peripherical length of a circular tube which has a diameter as large as the largest cross-sectional width of the expander. After the expansion the pressure is released, whereafter the expander, having been expanded over the larger part of its length or essentially all of its length, and thereby the entire device, is firmly anchored in the rock wall, by frictional engagement in the walls of the bore hole 30. The indentations 22 are deep enough so that there will remain indentations after the expansion, however being smaller than before the expansion. It is especially preferred to use the expander according to the invention in leaky, unstable or porous rock walls.

The next stage in the application of the device is to seal the bore hole with the device contained therein at the bottom end by tightening the nut 12 so that the rubber sleeve 10 is compressed in an axial direction, at which it expands in a radial direction to seal between the injection tube 3 and the lower walls of the bore hole, Fig. 4. A hose (not shown) can now be connected to the injection tube and the filling material 31 A is injected under positive pressure, at which the filling material flows out of the outlet openings 6 in the injection tube and penetrates into the bore hole at the upper diameter of the rubber sleeve 5. The rubber sleeve 5 acts here as a non-return valve integrated into the device so that the filling material, in spite of being under positive pressure, cannot run back out of the bore hole before it manages to harden. Beneficially, there is also arranged a small diameter pipe 35 along the device and preferably in a groove in the sleeve 10, e.g. a pipe of the type of a hydraulic pipe, which mouths in the inner part of the bore hole 30. Preferably it ends upstream of expander 20, as seen in the direction of flow for the filling material in the bore hole. The conduit 35 is arranged to act as a degassing conduit which leads air and gasses out of the bore hole as the filling material is introduced. During introduction of the filling material, the open end of the pipe 35 is sealed when filling material starts to continuously come out of this pipe, whereafter the introduction of filling material into the bore hole can proceed under a positive pressure.

Due to the positive pressure, filling material is also caused to penetrate any cracks 32 leading into the bore hole, in spite of the fact that these cracks may be water-bearing. The filling material will also penetrate into the remaining indentations 22 of the expander 20 and thereby act as a corrosion protection for the expander too. When the desired positive pressure, which may reach about 100 bar positive pressure or suitably about 50-

80 bar positive pressure, has been attained, the hose connection can be detached, at which the filling material 31 A can be left to harden under positive pressure, thanks to the non-return valve 4 and the rubber sleeve 10. When the filling material has hardened, the nut 12 is unscrewed, the washer 11 removed and the rubber sleeve 10 is taken out of the hole by means of the narrow tube 13 provided with a flange. The space below the flange 9 is then filled with filling material 3 IB (Fig. 5) by providing the opening of the bore hole with a larger washer (not shown) with a hole in one side for filling with filling material, air being made to evacuate the hole via an air pipe. If the risk of corrosion is not great, however, the narrow tube 13 provided with a flange can be left out of the device, in which case the rubber sleeve 10, washer 11 and nut 12 can instead remain permanently in place after the device has been applied to the bore hole. The opening of the bore hole and its immediate surroundings are then covered in a conventional manner with a plate, disc or washer 33, which is pressed against the rock wall by means of a nut 34, which is screwed on to the protruding part of the injection tube.

By means of the invention a relatively simple and cheap construction is achieved for sealing, the expander according to the invention being used in order to anchor the device in the bore hole and a the non-return valve function allowing filhng material to be injected into a bore hole and allowed to harden under a favourable positive pressure. The relatively simple and cheap construction also allows the seal, non-return valve and expander to be cast in the bore hole and thereby form an admittedly permanent but nevertheless disposable material without incurring costs which are too great. Corrosion- promoting air bubbles close to the reinforcement bar are counteracted due to the positive pressure. A further advantage of the device according to the invention is that it can be used for filhng material of varying viscosity or dry content according to the circumstances and preference.

The invention is not restricted to the embodiment described above but can be varied within the scope of the following patent claims. The man skilled in the art will thus easily perceive e.g. that the expander also may be used together with other types of rock bolts equipped with a non-return valve. An alternative in connection with the use of the invention is also that the expander is introduced first, being screwed to the top of a pipe, and is expanded by pressurisation. The tube is then screwed loose form the expander and the remaining part of the device is introduced into the bore hole, whereby the reinforcement bar, which then is threaded in the top end, is screwed to the expander.

Claims

1. Device for reinforcement and sealing of a rock wall, which device comprises a reinforcement bar (1) adapted to be introduced into a bore hole (30) in the rock wall, into which bore hole a filling material (31) is intended to be injected, and also comprises a non-return valve (4) for the filling material, characterized in that the device further comprises a tubular shaped expander (20) for anchoring the device in the rock wall, which expander, before the expansion, exhibits at least one, preferably at least two, axially extending indentations (22), whereby the expander has a peripherical length in its cross-section which exceeds the circumference of the bore hole (30), but has a largest diameter which is less than the diameter of the bore hole, said expander (20) being arranged to be expanded and thereby plastically deformed essentially without its peripherical length increasing, at anchoring of the device in the rock wall.

2. Device according to claim 1, characterised in that the expander (20) exhibits at least three, preferably at least four, axially extending indentations (22), which are preferably arranged at essentially equal intervals about the circumference of the expander.

3. Device according to claim 1 or 2, characterised in that bulgings (23) of the expander (20), which are situated between said indentations (22) have a softly curved shape, whereby they, in the part situated most distant from the centre line of the expander, take the shape of half a circular cylinder.

4. Device according to any of the above claims, characterised in that the expander (20) and thereby the device, is arranged to be anchored in the bore hole (30) when the expander is connected to an external source of pressurised liquid, via a hydraulic pipe (26).

5. Device according to any of the above claims, characterized in that said non-return valve (4) is adapted to withstand a positive pressure of the filling material (31) in the bore hole and is permanently connected in the device to the reinforcement bar (1) already before the reinforcement bar is introduced into the bore hole (30).

6. Device according to any of the above claims, characterized in that said non-return valve (4) comprises a sleeve (5), preferably of rubber, which encloses an injection tube (3) provided with outlet openings (6), which injection tube is preferably joined together with said reinforcement bar (1).

7. Device according to claim 6, characterized in that said sleeve (5) has the shape of the envelope of a truncated cone, its circumference at its narrowest short end being arranged sealingly around the injection tube (3).

8. Device according to any of the above claims, characterized in that said device, at the opening of the bore hole, is provided with a seal (10) arranged to act against the walls of the bore hole.

9. Device according to claim 8, characterized in that said seal (10) consists of a sleeve, preferably of rubber, which surrounds the injection tube (3) in a position upstream of said non-return valve (4), which sleeve is arranged to achieve a sealing effect against the walls of the bore hole (30) by being expanded in a radial direction when it is compressed in an axial direction, said sleeve (10) preferably being arranged to be removed when the filling material has hardened so that the space taken up by the sleeve can instead be filled with further filling material.

10. Method for reinforcement and sealing a rock wall, in which a reinforcement bar (1) and a non-return valve (4) for a filling material (31) is introduced into a bore hole (30) in the rock wall, into which bore hole the filling material is thereafter injected via the non-return valve, characterized in that said reinforcement bar (1) is anchored in the rock wall by a tubular shaped expander (20), which expander, before the expansion, exhibits at least one, preferably at least two, axially extending indentations

(22), whereby the expander has a peripherical length in its cross-section which exceeds the circumference of the bore hole (30), but has a largest diameter which is less than the diameter of the bore hole, said expander (20) being expanded and thereby plastically deformed essentially without its peripherical length increasing, at anchoring of the reinforcement bar (1) in the rock wall.