GB1564348A

GB1564348A - Packer for use with earth or rock anchors

Info

Publication number: GB1564348A
Application number: GB3993876A
Authority: GB
Original assignee: DIVIDAG STRESSED CONCRETE Ltd
Current assignee: DIVIDAG STRESSED CONCRETE Ltd
Priority date: 1977-10-03
Filing date: 1977-10-03
Publication date: 1980-04-10

Description

(54) IMPROVEMENTS IN OR RELATING TO A PACKER FOR USE WITH EARTH OR ROCK ANCHORS (71) We, DIVIDAG STRESSED CONCRETE LLMITED, a British Company, of Southam Industrial Estate, Southam, Leamington Spa, Warwickshire, do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to improvements in or relating to a packer for use with earth or rock anchors.

An earth or rock anchor usually comprises a rod, or like elongate element (known as a tendon) which is received in a borehole and is retained therein by means of a cement or a resin grout. The cement is injected into the borehole so as to fill the space between the surface of the borehole and the tendon over a desired length of the tendon (known as the bond length) adjacent the blind end of the borehole. This leaves the remainder of the tendon spaced from the side of the borehole over what is known as the free stressing length of the tendon. After the tendon has been cemented in the borehole, an anchor plate is mounted on the end of the tendon projecting from the borehole and is urged against the face of the material in which the borehole has been formed by, for example, screwing it along a screw thread formed on the tendon.

A difficulty which arises with the use of earth and rock anchors is the injecting of the cement over the bond length of the tendon when the blind end of the borehole is higher than the open end. Hitherto, it has been proposed to use a packer which can be located in an appropriate position on the tendon prior to inserting the tendon in the borehole and which can thereafter be inflated so as to engage the wall of the borehole when the tendon is in position.

Normally, the packer is inflated by air which is pumped into the packer through a conduit.

After inflation, the cement is pumped uphill into the space (referred to herein as the bonding space) between the packer and the blind end of the borehole through a further conduit, air in the bonding space being vented ot atmosphere through yet another conduit. Thus with such a system, three conduits are necessary. Furthermore, airinflated packers have been known to deflate when in use, and the cement which has been pumped into the bonding space has simply run out of the open end of the borehole. An object of the present invention is to provide an improved packer in which the foregoing disadvantages are substantially mitigated.

According to the invention, a packer for use with an earth or rock anchor comprises a packer support member locatable on a tendon of the earth or rock anchor, a permeable and flexible elongate tubular membrane secured around the periphery of the support member at positions spaced apart from each other to define a chamber between the membrane and the support member, duct means arranged alongside the support member for introducing in the chamber a settable mass of flowable material which includes solid praticles in a liquid medium and for enabling a further settable mass of said flowable material or a settable mass of different flowable material to be intro duced in a bonding ace between the packer and the blindendothe borehole, whereby, in use, the settable mass of flowable material will enter the chamber and cause the membrane to expand and engage the adjacent peripheral surface of the borehole in which the tendon is located to seal off the bonding space, the permeable membrane allowing liquid in said settable mass of flowable material to pass therethrough whilst leaving solid particles of the material in the chamber. In this manner, the solid particles in the chamber prevent deflation of the membrane.

In the case where the settable mass of flowable material to be introduced in the bonding space is the same as that to be introduced in the chamber, the said duct means preferably introduces the settable mass of knowable material in the bonding space and the chamber simultaneously. In such a case, the duct means may comprise a conduit which passes between the membrane and the support member, the conduit having an outer end which will be arranged in the bonding space and having one or more apertures in its wall to enable the settable mass of flowable material to enter the said chamber Preferably, the support member includes an elongate main tube having two relatively shorter outer tubes mounted thereon and spaced apart axially, said duct means extending between the outer periphery of the main tube and the inner peripheries of the outer tubes.The ends of the membrane are preferably held in sealing engagement with the outer tubes by fastening means. The fastening means may include resilient sleeves which fit over the ends of the membrane and which hold it in position on the outer tubes. In such a case, the membrane may be urged into sealing engagement with the outer tubes by means of tensioned bands which extend around the resilient sleeves.

Adhesive tape may be applied to the outer periphery of each outer tube so as to extend around the ends of the membrane.

The chamber for receiving the settable mass of flowable material is preferably defined between the membrane and the main tube.

The spaces between the main and outer tubes may be filled with resin grout or like material, in which material the duct means is embedded. An air outlet conduit may also be arranged between the main tube and the inner peripheries of the outer tubes so that it will extend into the bonding space when in use, said outlet conduit being embedded in said resin grout or like material.

Preferably the main tube and the outer tubes are cylindrical, the outer tubes being coaxial with their common axes parallel with the axis of the main tube. The membrane is preferably formed from a nonwoven fabric which may be spun bonded and formed by direct extrusion.

A packer in accordance with the invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a side elevation of one form of packer in accordance with the invention and shown partly in cross-section; Figure 2 is a cross-section of the packer shown in Figure 1 on the line II-II in Figure 1.

Figure 3 is a longitudinal cross-section through a borehole showing the packer in position on a tendon, and Figure 4 is an elevation of part of an alternative form of conduit for ducting a settable mass of flowable material.

An elongate plastics tube 1 (constituting the aforesaid main tube) is arranged eccentrically within two axially spaced plastics outer tubes 2. Two conduits 3, 4 extend through spaces defined between the tubes 1 and 2, the spaces being filled with resin grout 5. As seen in Figure 1, the conduits 3, 4 extend beyond each end of the tube 1.

In the example, the conduit 3 constitutes a duct for a settable mass of flowable material such as cement mortar or resin grout, and the conduit 4 acts as an air vent. A sleeve of permeable and flexible material 6 extends between each tube 2 and is secured thereto by means of suitably profiled rubber sheaths 7, 8. As seen in Figure 1, the sheaths 7, 8 overlap and an adjustable metal band 11 extends around the outer periphery of each sheath 7, the bands 11 being tensioned to draw the sleeve 6 into sealing engagement with the tube 2. Adhesive tape 9 is wound around each tube 2 and one end of the associated sheath 7. The sleeve 6 is preferably formed from a non-woven fabric of the spun-bonded type and which is made by direct extrusion. A suitable fabric has been found to be "BIDIM" manufactured by Rhone-Poulenc of France.A cement receiving chamber 10 is defined between the tube 1 and the inner surface of the sleeve 6, cement being introduced in the chamber through apertures 12 formed in the conduit 3.

In use, the tube 1 is slid on to a tendon 14 of an earth or rock anchor, and is positioned thereon so that when the tendon is inserted into a borehole 15, the correct bond length for the anchor will be defined adjacent the blind end of the borehole. After inserting the tendon in the borehole, cement which includes solid particles in a liquid medium is pumped under pressure through the conduit 3. Eventually, the cement reaches the apertures 12 and some of the cement in the conduit passes through the apertures 12 and into the chamber 10. The remainder of the cement continues along the conduit 3 and extrudes from the right-hand end 3a into a bonding space 16 of the borehole. Continued pumping of the cement causes the chamber 10 to fill and the sleeve 6 to expand until it engages the wall 13 of the borehole as shown in Figure 4 and in broken lines in Figure 1.

The permeable nature of the material forming the sleeve 6 allows the liquid to pass through the sleeve leaving the solid particles in the chamber 10. After the sleeve 6 has fully expanded as shown, cement will continue to extrude from the right-hand end of the conduit 3 and will fill the bonding space 16. Air in the bonding space is vented to atmosphere through the conduit 4 which extends to a position adjacent the blind end of the borehole 15 when the blind end is higher than the open end. The expanded sleeve 6 prevents cement from escaping from the bonding space 16, and there is no risk of the sleeve 6 deflating once the chamber 10 is full of cement.

Experiments have shown that the outlet end of the conduit 3 does not have to be of any special form. However, it is envisaged that the end of the conduit could be closed as shown in Figure 4 and a series of apertures 13 provided in the conduit 3 adjacent the closed end. By forming the conduit 3 in this manner, a greater pressure will be required to pump the cement into the borehole and any tendency for cement to by-pass the apertures 12 will be reduced. The sleeve 6 may, in practice, have to withstand pressures of up to 8 atmospheres.

The packer shown in Figure 1 could be simplified if necessary by omitting the sheaths 8 and, if desired, the sheaths 7. In the latter case, the material 6 would be held on to the tubes 2 by adhesive tape alone.

Although specific reference has been made to "BIDIM" as a suitable sleeve material, other flexible and permeable materials may be suitable for forming the sleeve provided that they are able to withstand the working pressure.

Whilst the packer described has two conduits 3, 4 the conduit 4 may be omitted in certain applications.

The tubes 1, 2 may be made from a material other than plastics.

We consider the present invention to be advantageous over known types of inflatable packer for two reasons, namely: 1. The danger of the sleeve 6 becoming deflated during injection of a settable mass of flowable material into the borehole is substantially overcome, and 2. A packer in accordance with the in vention does not require separate con duits for inflating the sleeve 6 and for ducting for settable mass of flowable material into the bonding space of the borehole. However, if, for any reason, different types of cement were required for filling chamber 10 and for filling the bonding space, separate conduits would be provided for ducting each type of cement.

WHAT WE CLAIM IS: 1. A packer for use with an earth or rock anchor comprising a packer support member locatable on a tendon of the earth or rock anchor, a permeable and flexible elongate tubular membrane secured around the periphery of the support member at positions spaced apart from each other to define a chamber between the membrane and the support member, duct means arranged alongside the support member for introducing in the chamber a settable mass of flowable material which includes solid particles in a liquid medium and for enabling a further settable mass of said flowable material or a settable mass of different flowable material to be introduced in a bonding space between the packer and the blind end of the borehole, whereby, in use, the settable mass of flowable material will enter the chamber and cause the membrane to expand and engage the adjacent peripheral surface of the borehole in which the tendon is located to seal off the bonding space, the permeable membrane allowing liquid in said settable mass of flowable material to pass therethrough whilst leaving solid particles of the material in the chamber.

2. A packer, according to Claim 1 and in the case where the settable mass of flowable material to be introduced in the bonding space is the same as that to be introduced in the chamber, in which the duct means introduces the settable mass of flowable material in the bonding space and the chamber simultaneously.

3. A packer, according to Claim 2, in which the duct means comprises a conduit which passes between the membrane and the support member, the conduit having an outer end which will be arranged in the bonding space and having one or more apertures in its wall to enable the settable mass of flowable material to enter the said chamber.

4. A packer, according to Claim 1, 2 or 3, in which the support member includes an elongate main tube having two relatively shorter outer tubes mounted thereon and spaced apart axially, said duct means extending between the outer periphery of the main tube and the inner peripheries of the outer tubes.

5. A packer, according to Claim 4, in which the ends of the membrane are held in sealing engagement with the outer tubes by fastening means.

6. A packer, according to Claim 5, in which the fastening means includes resilient sleeves which fit over the ends of the membrane and which hold it in position on the outer tubes.

7. A packer, according to Claim 6, in which the membrane is urged into sealing engagement with the outer tubes by means of tensioned bands which extend around the resilient sleeves.

8. A packer, according to Claim 5, 6 or 7, in which adhesive tape is applied to the outer periphery of each outer tube and extends around the ends of the membrane.

9. A packer, according to any of Claims 4 to 8, in which the chamber for receiving the settable mass of flowable material is

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. atmosphere through the conduit 4 which extends to a position adjacent the blind end of the borehole 15 when the blind end is higher than the open end. The expanded sleeve 6 prevents cement from escaping from the bonding space 16, and there is no risk of the sleeve 6 deflating once the chamber 10 is full of cement. Experiments have shown that the outlet end of the conduit 3 does not have to be of any special form. However, it is envisaged that the end of the conduit could be closed as shown in Figure 4 and a series of apertures 13 provided in the conduit 3 adjacent the closed end. By forming the conduit 3 in this manner, a greater pressure will be required to pump the cement into the borehole and any tendency for cement to by-pass the apertures 12 will be reduced. The sleeve 6 may, in practice, have to withstand pressures of up to 8 atmospheres. The packer shown in Figure 1 could be simplified if necessary by omitting the sheaths 8 and, if desired, the sheaths 7. In the latter case, the material 6 would be held on to the tubes 2 by adhesive tape alone. Although specific reference has been made to "BIDIM" as a suitable sleeve material, other flexible and permeable materials may be suitable for forming the sleeve provided that they are able to withstand the working pressure. Whilst the packer described has two conduits 3, 4 the conduit 4 may be omitted in certain applications. The tubes 1, 2 may be made from a material other than plastics. We consider the present invention to be advantageous over known types of inflatable packer for two reasons, namely: 1. The danger of the sleeve 6 becoming deflated during injection of a settable mass of flowable material into the borehole is substantially overcome, and 2. A packer in accordance with the in vention does not require separate con duits for inflating the sleeve 6 and for ducting for settable mass of flowable material into the bonding space of the borehole. However, if, for any reason, different types of cement were required for filling chamber 10 and for filling the bonding space, separate conduits would be provided for ducting each type of cement. WHAT WE CLAIM IS:

1. A packer for use with an earth or rock anchor comprising a packer support member locatable on a tendon of the earth or rock anchor, a permeable and flexible elongate tubular membrane secured around the periphery of the support member at positions spaced apart from each other to define a chamber between the membrane and the support member, duct means arranged alongside the support member for introducing in the chamber a settable mass of flowable material which includes solid particles in a liquid medium and for enabling a further settable mass of said flowable material or a settable mass of different flowable material to be introduced in a bonding space between the packer and the blind end of the borehole, whereby, in use, the settable mass of flowable material will enter the chamber and cause the membrane to expand and engage the adjacent peripheral surface of the borehole in which the tendon is located to seal off the bonding space, the permeable membrane allowing liquid in said settable mass of flowable material to pass therethrough whilst leaving solid particles of the material in the chamber.

defined between the membrane and the main tube.

10. A packer, according to any of Claims 4 to 9, in which the spaces between the main and outer tubes are filled with resin grout or like material, in which.

material the duct means is embedded.

11. A packer, according to Claim 10, in which an air outlet conduit is also arranged between the outer periphery of the main tube and the inner peripheries of the outer tubes so that it will extend into the bonding space wherein use, said outlet conduit being embedded in said resin grout or like material.

12. A packer, according to any of Claims 4 to 11, in which the main tube and the outer tubes are cylindrical, the outer tubes being coaxial with their common axes parallel with the axis of the main tube.

13. A packer, according to any preceding claim, in which the membrane is formed from a non-woven fabric.

14. A packer, according to Claim 13, in which the non-woven fabric is spun bonded and formed by direct extrusion.

15. A packer, constructed and arranged substantially as described herein with reference to and as illustrated in Figures 1, 2 and 3 or as illustrated in Figures 1, 2 and 3 when modified according to Figure 4 of the accompanying drawings.