EP1017926A1

EP1017926A1 - Injection device and injection method

Info

Publication number: EP1017926A1
Application number: EP98917878A
Authority: EP
Inventors: Ivan Seibert Andersson
Original assignee: Skanska Sverige AB
Current assignee: Skanska Sverige AB
Priority date: 1997-04-10
Filing date: 1998-04-09
Publication date: 2000-07-12
Also published as: EA199900919A1; JP2001518998A; CN1258335A; WO1998045576A1; AU7092698A; CA2286025A1; PL336121A1; AU722633B2; SE9701325D0; SE9701325L; NO994885D0; NO994885L; SE509139C2

Abstract

Cracks round a bore hole (19) are sealed while at the same time a rock bolt (20) is anchored in the bore hole by injecting a sealing material (23) through an injection nozzle. This comprises a sealing sleeve (10-14) with a through hole and a nonreturn valve device and is left in the bore hole after injection. The rock bolt (20) is inserted through the through hole of the valve nozzle and through the nonreturn valve device (16, 20). According to the invention, one sealing element of the non return valve device is formed of the rock bolt (20) and its other sealing element is formed of a sealing socket (16). This is pressed in a yielding and sealing manner against the rock bolt. The injection of the sealing material (23) is carried out through a gap (21) between the rock bolt and the sealing sleeve (10-14) and through the non return valve device (16, 20) during elastic deformation of the sealing socket (16).

Description

INJECTION DEVICE AND INJECTION METHOD

When making, for instance, tunnels and rock chambers in rocks, it is necessary for rock cracks to be sealed, for instance, to counteract penetration of water and, thus, groundwater lowering or to make it possible to prevent liquid from escaping if the tunnels or rock chambers are used for storing or transporting liquids. It is common to carry out sealing by injecting cement or some other sealing material, e.g. plastic, at high pressure into bore holes. Several devices have been suggested for carrying out such injection. One example is disclosed in SE-B-413,929 and the counterpart US-A-4 , 260, 295. According to these publications, use is made of an injection nozzle, which can be disconnected from the actual injection device and be left in the bore hole after injection. The nozzle has a lip seal or an expandable sleeve of elastomeric material which is sealingly pressed against the surrounding bore hole wall on the one hand to secure the nozzle and, on the other hand, to permit injection without injected material escaping between the nozzle and the bore hole wall. The seal or sleeve therefore permits high pressure to be maintained in the bore hole during the injection procedure .

This prior-art device functions well when it is merely a matter of sealing cracks in the rock. When making tunnels or rock chambers, it is in many cases necessary that rock bolts be fixed to the rock wall. After the sealing procedure by using, for instance, the prior-art device according to the above-mentioned patent specifica- tions, a further bore hole is in such a case bored just adjacent to the bore hole which was used to seal cracks in the rock. Unfortunately it happens quite often that water leaks through the new bore hole and that a renewed injection therefore is required. This problem is particu- larly pronounced if the water pressure in the rock round the tunnel or rock chamber is high and the rock has many large or small cracks. The injection procedure must in such cases be repeated until sufficient tightness has been obtained for the bore hole, in which the rock bolt is to be inserted, to be dry. When dryness has been achieved, the rock bolt can be anchored either by being designed as an expansion bolt (e.g. according to US-A- 4,290,515) or by first injecting cement mortar into the bore hole and then pressing in the rock bolt. The latter procedure is complicated since the rock bolt in many cases can have a considerable length, usually 3-4 m if the rock is of poor quality with many cracks. The difficulties arise mainly because the injected amount of cement mortar must be carefully adjusted to the dimensions of the bore hole and the rock bolt, such that a complete filling of the bore hole is obtained round the inserted rock bolt without pressing too much mortar out of the hole while pressing in the rock bolt. According to US-A-4 , 289, 427 , attempts have been made to counteract this problem by replacing the rock bolt with a cable which is inserted into the bore hole. For this purpose a special type of cable is used, which is made of glass fibres and has one or more ventilation ducts extending in the longitudinal direction. The cable is rotated during its insertion into the bore hole, and at the same time the area round the opening of the bore hole is sealed by pressing an annular sealing disk against the rock wall. An injection device is used to inject at high pressure a sealing compound into the bore hole. The insertion of the sealing compound is ensured on the one hand by the rotation of the cable and, on the other hand, by excess air in the bore hole being emitted through said ventilation ducts. After solidification of the sealing compound, the cable can be used for anchoring purposes, for instance, in connection with the casting of a continuous concrete layer on the inside of the rock. Admittedly, this prior-art technique can be used for the anchoring of cables, but it is not suited for the anchoring of rock bolts. Moreover, it is difficult to achieve sufficient tightness between the sealing ring and the adjoining rock surface since, for natural reasons, the rock surface is rough.

An object of the present invention therefore is to provide a method of anchoring a rock bolt in a bore hole in a rock wall while simultaneously injecting a sealing compound.

One more object of the invention is to provide a method of sealing a rock while simultaneously anchoring rock bolts and sealing the rock formation by injecting a sealing compound. A further object of the invention is to minimise the need for injection of a rock by simultaneous sealing of the rock formation and anchoring of the rock bolts.

According to the invention, these and other objects are achieved by a method and a device according to the independent claims 1 and 2, respectively. The dependent claims define particularly preferred embodiments of the invention.

Summing up, the invention resides in the idea of simultaneously sealing cracks round bore holes and anchoring a rock bolt in the bore hole by injecting a sealing material through an injection nozzle. The injection nozzle comprises a sealing sleeve with a through hole and a nonreturn valve device and is left in the bore hole after injection. The rock bolt is inserted through the through hole of the valve nozzle and through the nonreturn valve device. According to the invention, one sealing element of the nonreturn valve device is formed of the rock bolt and its other sealing element is formed of a sealing socket. This is pressed in a yieldable, sealing manner against the rock bolt. The injection of the sealing material is carried out through a gap between the rock bolt and the sealing sleeve and through the non- return valve device during elastic deformation of the sealing socket.

Two embodiments of a method and a device according to the present invention will now be described in more detail with reference to the accompanying drawings, in which

Fig. 1 is a longitudinal section of an embodiment of an injection nozzle designed according to the invention; Fig. 2 shows this injection nozzle when used in a bore hole for simultaneous anchoring of a rock bolt and injection of an injection compound; and Fig. 3 illustrates a further embodiment of an injection nozzle according to the present invention. The embodiment of an inventive injection device shown in the drawing comprises an elongate sleeve 10 which is externally threaded at its one end and at its other end is rigidly connected to or integrated with an outwardly directed flange 11. A sealing element 12 in the form of a piece of tube of an elastomeric material is slipped onto the sleeve 10. This sealing element has at each end a washer 13, which preferably is fixedly connected to the end surface of the sealing element.

A pressure transferring sleeve 15 is placed between the sleeve 10 and a nut 14 threaded onto this. A sealing socket 16 is fixed by vulcanisation to the outwardly directed side of the flange 11 (to the left in Fig. 1) . The socket is made of an elastomeric material and has a through hole 17 with at least one portion with a smaller diameter than the inner diameter of the sleeve 10. In the embodiment shown, the through hole 17 of the socket also tapers conically in the direction of the outlet end, two inwardly directed sealing ridges 18 being formed in the through hole. These sealing ridges need not be semi-cir- cular in cross-section but may also be designed as inwardly projecting sealing lips. When this injection device is to be used, a hole 19 is first bored in the rock wall. The bore hole can have the desired diameter, e.g. about 64 mm, and the desired depth, e.g. 3-4 m, which is common in this context. Then the nozzle of the injection device is inserted into the bore hole, the nut 14 being screwed in such that the sleeve 12 is compressed in the longitudinal direction to bulge outwards and sealingly be pressed against the wall of the rock hole. The tightening of the nut can be carried out in a prior-art manner, for instance, as shown in the above-mentioned US-A-4, 260, 295. If the bore hole has a diameter of 64 mm, a suitable outer diameter of the piece of tube 12 can be 57 mm.

Having anchored the nozzle in this way in the bore hole 19, a rock bolt 12 is inserted through the nozzle. The diameter of the rock bolt 20 should be smaller than the inner diameter of the sleeve 10 in order to leave an annular gap 21 between the bolt and the sleeve. Moreover, the through hole 17 of the socket 16 has a minimum diame- ter which is smaller than the outer diameter of the rock bolt, such that the socket 16 will be expanded during the insertion of the rock bolt and will therefore be sealingly pressed against the rock bolt. If the socket 16 is made of a rubber material, the rock bolt can have a dia- meter of 22 mm, the narrowest section of the socket 16 suitably being 20 mm. If the rock bolt 20 has a diameter of 22 mm, a suitable inner diameter of the sleeve 10 can be 32 mm, such that the annular gap 21 has a width of 5 mm. Having pressed the rock bolt into the bore hole through the injection nozzle, injection equipment 22 is connected to the sleeve 10. In the embodiment shown, the projecting portion of the rock bolt is completely enclosed in the injection equipment 22, but it is pos- sible to design this equipment such that the rock bolt extends through the equipment and projects therefrom. In that case, a seal must be established also round the projecting end of the rock bolt.

By means of the injection equipment, a suitable sealing material 23, e.g. cement grout, is pressed into the injection nozzle, the sealing material flowing through the gap 21 and out through the socket 16, which expands elastically under the action of the pressure in the sealing material. The sealing material 23 fills the bore hole 19 round the rock bolt 20 and escapes in the usual manner through large and small cracks in the rock hole wall to seal the rock and prevent any flow of water out through the bore hole and the surrounding rock wall. When the injection has been finished, the injection equipment 22 is disconnected from the sleeve 10. Also the injection nozzle is therefore left in the bore hole, as is the case with the injection equipment according to US-A-4,260,295.

By the provision, according to the invention, of a different nonreturn valve than the one used in said US patent specification, it has become possible to carry out injection and anchoring of the rock bolt in one and the same operation. According to the invention, use is made of the rock bolt as one component of a nonreturn valve, whose other component is the sealing socket 16. By the sealing socket 16 being affected by the pressure in the injected bore hole, this pressure will keep it sealingly pressed against the rock bolt, such that the sealing compound is prevented from escaping and instead remains in the hole while the sealing compound hardens or solidi- fies. This is the case independently of whether the sealing compound is based on an inorganic or an organic sealing material. The preferred sealing compound is a cement grout, but also liquid or semi-liquid plastic materials can be used for this purpose. Fig. 3 shows another embodiment of an injection nozzle according to the present invention. The components corresponding to those in Figs 1 and 2 have been given the same reference numerals in this Figure.

Like the nozzle according to Figs 1 and 2, the injection nozzle according to this embodiment has a threaded sleeve 10. At one end of this sleeve there is flange 25 which is screwed onto or fixed in some other way to the sleeve. One end surface of the sealing element 12 abuts against or is preferably fixed by vulcanisation to this flange. At the other end of the sealing element there is a further end flange 26, which is displaceable along the sleeve 10. At least one lock washer 27 abuts against the outside of this end flange. This lock washer or these lock washers are such as to engage the threads of the sleeve and allow displacement of the washer/ washers merely in one direction of the sleeve (in this case, to the left in respect of the drawing) .

When the sealing element 12 is to be expanded to engage the surrounding bore hole wall, use is made of the same procedure as in the embodiment according to Figs 1 and 2. The difference is that the washer or washers 27 replace the sleeve 15 and the nut 14.

The flanges 25, 26 have a bevelled portion 28, which faces the sealing element 12. This is designed correspondingly. The reason for the bevelling is that the sealing element is better held in place while it expands. With a suitable design of the angle of bevel, it is therefore possible to eliminate the need for fixing the sealing element by vulcanisation to the end flanges, even if fixing by vulcanisation is preferred. A further difference of this embodiment from the one according to Figs 1 and 2 is that a pressure-equalising duct 29 is available, which extends through the sealing socket 16 and the flange 27 to connect the space 30 between the outside of the sleeve 10 and the inside of the sealing element 12 to the portion of the bore hole 19 inside the injection nozzle. During injection through the gap 21 and the through hole 17 and hence an increase of pressure behind the injection nozzle, liquid material in the injection material will be pressed through the connecting duct into this space 30. The volume of the space increases when compressing the sealing element 12 by means of the flanges 25, 26. This results in the space 30 being filled with liquid material. The liquid material is essentially non-compressible and will therefore improve the securing of the injection nozzle to the bore hole wall, thereby decreasing the risk of the nozzle being pressed outwards in the direction of the inlet opening of the bore hole.

The embodiment in Fig. 3 therefore is the currently most preferred.

The remaining components of the injection device according to Fig. 3 can be designed in the same manner as in the embodiment according to Figs 1 and 2. Thus, the through opening 17 for the rock bolt 20 can have internal flanges or sealing ridges corresponding to the ridges 18 in Figs 1 and 2. In the embodiment according to Figs 1 and 2, the sealing socket 16 is fixed by vulcanisation to the flange 11. In the embodiment according to Fig. 3, the socket 16 can be fixed by vulcanisation to the flange 25 in a corresponding manner, such that the flange 25 will be connected to the sleeve 10 when it is screwed onto the same.

The bevelled surfaces 28 of the flanges 25,26 counteract a possible tendency of the sealing element 12 to move, while being compressed longitudinally, radially outwards relative to the flanges 25, 26.

Claims

1. A method of simultaneously sealing cracks round a bore hole (19) and anchoring a rock bolt (20) in the bore hole, in which method injection of a sealing material (23) is carried out through an injection nozzle which has a sealing sleeve (10-14) with a through hole and a nonreturn valve device and which is left in the bore hole after injection, c h a r a c t e r i s e d in that the rock bolt (20) is inserted, on the one hand, through the through hole of the valve nozzle while leaving a gap (21) between the hole and rock bolt and, on the other hand, through the nonreturn valve device (16, 20) , whose one sealing element is formed of the rock bolt (20) and whose other sealing element (16) is yieldably pressed in a sealing manner against the rock bolt, and that the injection of the sealing material (23) is carried out through said gap (21) and through the nonreturn valve device (16, 20) into the bore hole (19) .

2. An injection device for injecting a sealing material (23) into a bore hole (19), comprising an injection nozzle with a sealing sleeve (10-14) which is expandable towards the surrounding bore hole, and a nonreturn valve device (16, 20) , the injection nozzle having a through hole and the nonreturn valve device (16, 20) being arranged at the injection nozzle end facing the bore hole, c h a r a c t e r i s e d in that the sealing elements (16, 20) of the nonreturn valve device are formed of a sealing socket (16) which is arranged at the injection nozzle end facing the bore hole (19) and which is made of an elastomeric material and has a through hole (17) which is connected to the through hole of the injection nozzle, the through hole of the injection nozzle having a larger diameter than a rock bolt (20) intended to be used together with the injection device, and the through hole (17) of the sealing socket (16) having one or more portions with a smaller diameter than said rock bolt to be elastically pressed against the rock bolt and, together therewith, constitute the nonreturn valve device (16, 20) .

3. An injection device as claimed in claim 2, c h a r a c t e r i s e d in that the through hole (17) of the sealing socket (16) tapers away from the through hole of the injection nozzle.

4. An injection device as claimed in claim 2 or 3, c h a r a c t e r i s e d in that the sealing socket (16) on its inside has inwardly projecting sealing ridges or lips (18) to be pressed against the rock bolt (20) .

5. An injection device as claimed in claim 2, 3 or 4, c h a r a c t e r i s e d in that a through duct (29) extends between the side of the sealing socket

(16) facing the bore hole (19) and a space (30) between a sealing element (12) included in the sealing socket (10-14) and a through sleeve (15) included in the sealing socket (10-14).