WO2007144595A1

WO2007144595A1 - Method of reinforcing a structure and apparatus therefor

Info

Publication number: WO2007144595A1
Application number: PCT/GB2007/002167
Authority: WO
Inventors: Peter James
Original assignee: Cintec International Limited
Priority date: 2006-06-12
Filing date: 2007-06-12
Publication date: 2007-12-21
Also published as: GB0611548D0

Abstract

Disclosed is a method of reinforcing a structure (10). The structure (10) has an elongate hole, e.g. a drilled hole (14) therein and the method includes inserting into the hole an elongate reinforcement core (20) carrying over at least part of its length an expandable sock (30), then introducing a settable liquid, e.g. cementious grout (40), into the sock (30) at a first pressure so as to cause expansion of the sock (30) toward the wall (18) of the hole. The sock (30) is formed from a material which is permeable to the grout (40) so as to allow the grout (40) to seep through the sock. The method includes the step of reducing the pressure in the hole to a second pressure lower than the first pressure, so as to encourage the grout to seep through the sock. In practice the second pressure can be below atmospheric pressure and can be attained by sucking the grout out of the hole.

Description

Method of reinforcing a structure and apparatus therefor

This invention relates to the reinforcing of structures particularly those of brick, masonry or concrete. It is a known technique to reinforce such a structure by drilling an elongate hole into it, inserting a rigid bar or rod covered in a fabric sleeve or sock, and injecting it with cementious grout. The grout expands the sleeve under pressure to fill the space around the rod and some grout seeps through the fabric sleeve to bond to the wall of the drilling when set. Such a technique is described in EP1152102. The sock provides a restriction of the liquid grout to inhibit undesirable flow into cracks or cavities in the structure, other than the hole itself.

However, although the grout expands to fill the drilling, its seepage through the fabric sleeve is often not complete because the sock necessarily has to restrict the flow grout.

The result of the incomplete seepage of the grout through the sleeve is that an ineffective or partially effective bond is produced between the grout and the wall of the drilling. The strength of the reinforced structure could be improved if the seepage through the fabric sleeve were improved. One answer to the above mentioned problem is to increase the injection pressure of the injected grout. However, increasing the injection pressure leads to an increased pressure in the drilling. There is then a risk of damaging the structure to be reinforced when pressure is increased in the drilling, because the increased pressure may force the structure apart, particularly when the drilling is close to the surface of the structure. Another problem associated with increasing the pressure is that the sock, under pressure, acts like a rigid member which can distort the structure and cause undesirable internal stresses in the structure when the reinforcing takes place. Another problem associated with the known technique mentioned above is that bubbles and pockets of air form in the grout when the reinforcing takes place. These bubbles and pockets result in a reinforced structure which is weaker than a structure having no bubbles or pockets.

According to the present invention there is provided a method of reinforcing a structure having an elongate hole comprising; inserting into the hole an elongate reinforcement core carrying over at least part of its length an expandable sock, introducing a settable liquid into the sock at a first pressure so as to cause expansion of the sock toward the wall of the hole, the sock being formed from a material which is permeable to the liquid so as to allow the liquid to seep through the sleeve, characterised in that at the same time as the liquid is introduced into the sock the pressure in the hole is reduced to a second pressure lower than the first pressure so as to encourage the liquid to seep through the sock, to substantially fill the hole.

Preferably the first and second pressures cause a pressure differential between inside of the sock and the outside of the sock such as to cause flow of liquid from the inside the sock to the outside of the sock, but to inhibit pressure build-up in the sock and on the wall of the hole resulting from the first pressure. Preferably the method includes the step of causing the removal of bubbles or pockets of air from the grout during its introduction into the hole.

Preferably the hole has an opening at a surface of the structure and terminates at an opposite end of the hole. Preferably the liquid is introduced adjacent to the other end of the hole by means of a tube and the pressure reduction takes place at or adjacent to the surface of the structure.

More preferably the hole has an axis and an hole wall and the pressure reduction is caused to take place initially between the wall and the axis, and more preferably between the wall and the unexpanded sock. Preferably the liquid is in the form of a cementious grout.

Preferably the elongate reinforcement core is in the form of a single or multiple metal bars or rods.

Preferably the liquid/grout is forced into the hole under pressure along the tube to said other end. Preferably the first pressure is above atmospheric pressure and the second pressure is below atmospheric pressure.

Preferably a plate is provided at the surface of the structure to provide a closed cavity in the hole to maintain a vacuum therein.

Preferably the hole is formed by drilling. Thus in embodiments of the invention, in producing a vacuum within the drilling the seepage of the liquid or grout through the sleeve to make contact and bond with the wall of the drilling is increased. This results is increased strength of the reinforced structure when the liquid or grout has set because there is a better bond between the reinforcing core and the structure at the wall of the drilling. The overall internal pressure in the drilling is reduced during reinforcement also.

An embodiment of the invention will now be described by way of example, with reference to the drawings, in which Figure 1 a shows apparatus for carrying out the invention;

Figure 1b shows a section through the apparatus shown in Figure 1a; Figures 2 and 3 show further stages of the invention. Figure 1a shows a section through a structure 10. This structure is typically a wall, bridge arch, masonry, ornament or other structure which includes non man-made structures. Generally, such structures are produced from bricks, blocks, stone or other materials bonded together by mortar or the like. The structure is to be reinforced and has been drilled to produce an hole 14 by diamond drilling from a surface 12. The hole 14 terminates in this instance blindly at the opposite end 16. The hole 14 includes an inner wall surface 18. In order to reinforce the structure a reinforcing core, shown generally at

20, is inserted into the hole 14. A section through the reinforcing core 20 is shown in Figure 1b. The reinforcing core 20 includes four stainless steel reinforcing rods 22 held together by end plates 24. In this instance the end plates 24 are welded to the rods 22. The end plate 24 nearest to the surface 12 includes also an aperture 26 which allows grout tube 28 to pass therethrough.

The reinforcing core 20 includes also a flexible fabric sleeve or sock 30 which loosely surrounds the reinforcing element and is secured to each end plate 24. The sleeve is made of synthetic fibres woven into tubular form. In use the reinforcing core 20 is slid into the structure 10 along axis A together with tube 28 located in the middle of the core 20 and the sleeve 30. A sealing plate 32 is then positioned over the hole 14 and tube 28 extends through the sealing plate 32. The sealing plate 32 includes an elastomeric seal 36 which provides a substantially airtight seal around the opening of the hole 14 at the surface 12.

Once the reinforcing core 20 is located within the hole 14 and the sealing plate 32 has been fitted, cementious grout 40 is pumped under pressure a pressure of approximately 150 to 450 KPa (preferably about 300 KPa) along tube 28 to the far end 16 of the hole 14. The grout emerges from the tube 28 at its end 42 and fills the sleeve 30 so that the sleeve expands to make contact with the wall 18 of the hole 14. At the same time a vacuum pump 44 is used to evacuate hole 14 via evacuation tube 36 (i.e. reduce its pressure below atmospheric pressure 100KPa). The evacuation of the hole 14 improves the seepage of the grout 40 through the fabric of the sleeve 30 and inhibits an undesirable build-up of pressure in the hole.

Figure 2 shows the sleeve 30 completely expanded by grout 40 such that the sleeve expands fully to the extent of the hole 14. At this stage the grout tube 28 may be removed or left in situ. Sealing plate 32 along with vaccum tube 36 may be removed also.

Figure 3 shows the finished, reinforced, structure with the reinforcing core 20 grouted in position and fixedly secured to the side wall 18 of the hole 14 by means of the grout 40 which has made superior contact with the wall 18 as a result of the evacuation of the hole 14 during the application of the grout into the hole 14. It will be noted that in this instance the tube 28 has been removed.

Various modifications or alternatives to the embodiment described above will be apparent to the skilled addressee. In particular, other materials than those described may be used. The cementious grout may be replaced with any other settable material for example a polymer material. The bars 22 of the core 20 could be replaced by any number of bars including a single, possibly central, bar and the reinforcing core may project from the surface 12 once it has been inserted e.g. to provide a threaded anchor. The grout etc. insertion tube 28 and vacuum tube 36 may be positioned anywhere to provide effective application of the grout and evacuation of the 14 respectively. The grout tube may be formed integrally with the reinforcement core. In practice it is likely that the vacuum tube may be filled with grout etc. and therefore it is possible that such grout may be recycled and pumped back into the hole in a closed circuit. More advantageously, a grout pump may be provided which also acts as a vacuum generating means and in such an instance may be connected to the vacuum tube 36.

Claims

1. A method of reinforcing a structure having an elongate hole comprising; inserting into the hole an elongate reinforcement core carrying over at least part of its length an expandable sock, introducing a settable liquid into the sock at a first pressure so as to cause expansion of the sock toward the wall of the hole, the sock being formed from a material which is permeable to the liquid so as to allow the liquid to seep through the sleeve, characterised in that the pressure in the hole is reduced to a second pressure lower than the first pressure so as to encourage the liquid to seep through the sock, to substantially fill the hole.

2. A method as claimed in claim 1 wherein the first and second pressures cause a pressure differential between inside of the sock and the outside of the sock such as to cause flow of liquid from the inside the sock to the outside of the sock, but to inhibit pressure build-up in the sock and on the wall of the hole resulting from the first pressure.

3. A method as claimed in claim 1 or 2 wherein the method includes the step of causing the removal of bubbles or pockets of air from the grout during its introduction into the hole.

4. A method as claimed in any one preceding claim wherein the hole has an opening at a surface of the structure and terminates at an opposite end of the hole.

5. A method as claimed in claim 4 wherein the liquid is introduced adjacent to the opposite end of the hole by means of a tube and the pressure reduction takes place at or adjacent to the surface of the structure.

6. A method as claimed in any one preceding claim wherein the liquid is forced into the hole under pressure along the tube to said opposite end.

7. A method as claimed in any one preceding claim wherein the hole has an axis and wall and the pressure reduction is caused to take place initially between the wall and the axis, and preferably between the wall and the unexpanded sock.

8. A method as claimed in any one preceding claim wherein the liquid is in the form of a cementious grout.

9. A method as claimed in any one preceding claim wherein the elongate reinforcement core is in the form of a single or multiple metal bars or rods.

10. A method as claimed in any one preceding claim wherein the first pressure is above atmospheric pressure and the second pressure is below atmospheric pressure.

11. A method as claimed in any one preceding claim wherein a plate is provided at the surface of the structure to provide a closed cavity in the hole to maintain a vacuum therein.

12. A method as claimed in any one preceding claim wherein the hole is formed by drilling.