A METHOD OF INSTALLING A SOIL ANCHOR AND A SOIL ANCHOR

Abstract: A soil anchor body (11) of folded sheet steel is hammered down into the soil by means of a rock drill rig. It carries with it a hose (19) coupled to its rear end and one or more steel ropes (29) deviated over its front end. The drill rod is withdrawn and cement grout is injected through the hose into the anchor body to inflate it. The steel ropes are now anchored and both ends of each rope are above ground and ready to be used to take tension load. If the soil anchor is only temporary used, the steel ropes can be withdrawn simply by being pulled at one end.

Description: A METHOD OF INSTALLING A SOIL ANCHOR AND A SOIL ANCHOR. This invention relates to a method o installing a sail anchor by drivi down an expansible anchor body of folded metal sheet into the ground b means of a rod or tube and then pressurizing the body to develop the folds and expand the body. It also relates to an anchor body. An anchor body and a method of this kind are described in EP 0112316-A In practice, a tube is used for driving down the anchor body and then is used for injecting cement grout into the anchor body to expand the body. One or more reinforcing rods or stiff steel ropes or the like ar forced down through the tube and into the anchor body and theyare then used to take the tension load. This method is being used and it is outstanding. It is, however, a disadvantage that the anchor cannot be used until th cement grout has hardened which takes days or almost a week. It is als sometimes a disadvantage that the tube with its tension load carrying elements will remain in the soil and that it cannot be dug up without first being cut into pieces. It is an object of the invention to make an anchor of this kind less costly and to make possible the use of an anchor almost immediatly it has been installed. It is also an object to make it possible to take u the anchor except for the anchor body fast and easily. The invention will be described with reference to the drawings. Fig 1 shows an anchor while driven into the soil Fig 2 shows the same anchor expanded Fig 3 shows the same anchor while being dismounted Fig 4 shows enlarged the front end of the anchor shown in Figs 1-3 Fig 5 is a section along the lines 5-5 in Fig 4 In Figs 1-3, an expansible anchor body 11 is shown. It is generally of the kind described in EP-0112316-A and will therefore not be described in detail but EP-0112316-A is incorporated by way of reference. The anchor body 11 is made of two steel sheets that are welded together along their longitudinal edges and folded in a zig zag form so that th form a cylindrical pole with rectangular or quadratic cross section(Fi 1). A cup 12 covers and seals the front end of the pole and an annular cup 13 surrounds the rear upper end of the pole. Four flats 14 are welded to the cups 12,13. There is a sealing viscos agent, for example asphalt, in the cups 12,13 and the cups are held together by the flats 14. A solid steel block 15 is welded to the rear cup 13 and it has a blind bore 16 for the end of a rock drill extension rod 17 and a bore with a fitting for a hose 19. The bore 18 ends in the center of the annular cup 13, that is, it is open to the interior space of the folde steel sheets. When a pressure fluid, for example cement grout, is supplied under pressure through the hose 19, the folded sheet metal bo lldevelops into a circular cylinder with conical ends (Fig 2). During this inflation, the flats 14 still hold the cups 12, 13 in place. Figur 4 shows the front end of the anchor body 11. A part of a pulley 2 with three grooves for three tension lines, for example steel ropes or strands, is welded to the cup 12. It is protected by a steel plate 23 that is carried by two rigid bolts 24,25 that are also welded to the cu 12. A bow-formed plate 26 is supported by support plates 27,28 welded t the plates 23,26. In Figures 1-3, one of three parallel steel ropes 29 can be seen. They are deviated over the bow-formed support 22 (the part of a pulley). A sequence for the installation of the anchor will now be described. The hose 19 is coupled to the block 15 and the three parallel steel ropes 29 are inserted between their bow-formed support 22 and their bow formed protection plate 26. A conventional crawler drill rig with a roc drilling machine can advantageously be used to hammer down the anchor body 11 with the end of the drill rod 17 inserted in the blind bore 16 of the block 15. The rotation should of course be off. The anchor body pulls the hose 19 and the three steel ropes 29 with it as it is forced down into the soil. When the anchor body has reached a competent layer the drill rod, which is a conventional extension rod, is withdrawn and conventional cement grout pump is coupled to the hose 19 and cement grout is injected into the anchor body 11 to inflate it, The steel rop 29 are forced outwardly by the anchor body 11 and their deviation angl is reduced, The six ends of the steel ropes can be coupled and tension loaded almost immediately since they will only apply compressive force on the anchor body and the cement grout can stand the compressive forc almost immediately. The flats 14 will be between the ropes 29 and the anchor body 11 which is advantageous since it will distribute the load It is an advantage that the ropes are not loaded until their angle of deviation has been reduced due to the inflation of the anchor body 11. The two ends of each rope should be equally tension loaded in order to avoid slippage in the rope support 22 at the front end of the anchor body 11. Most anchors are used only temporary and it is an advantage that the steel ropes can be withdrawn when the anchor has been used. As can be seen in Figure 3, simply by pulling one end of the rope the rope can b withdrawn. The rope will slide in its support 22. A modified steel rope arrangement is shown in Figures 6-8. Four steel ropes 29 are coupled to a yoke 40 at the front end of the anchor bod 11. By pulling only one or two of the ropes, the yoke will detach from the anchor body and the ropes and the yoke can be pulled out of the soil.

Claims: Claims 1. A method of installing a soil anchor by driving down an inflatable anchor body (11) of folded metal sheet into the ground by means of a ro and then pressurizing the body to develop the folds and expand the body characterized by the steps of coupling a tension line (29) and a pressure hose (19) to the anchor bod (11) so that the anchor body takes them with it into the ground, withdrawing the rod, expanding the anchor body by pressurizing it through the hose, and tensioning the line. 2. A method according to claim 1, characterized by coupling the line (29) to the anchor body (11) outside of the body, 3. A method according to claim 2, characterized by deviating the line (29) about the front end of the anchor body (11) to couple it to the anchor body so that there will be two ends of the line above ground. 4. A method according to claim 3, characterized by coupling two or more lines (29) in parallell to the anchor body (11). 5. A method according to claim 3 or 4, characterized by mounting a bow- formed line support (22) on the front end of the anchor body (11) and deviating the line (29) about the support. 6. A method according to any one of claims 3 to 5 for installing a temporary soil anchor, characterized by the step of pulling one end of the line (29) to get the line out of the ground when the anchor has been used. 7. A etod according to any one of claims 2 to 6 for installing a temporary soil anchor, characterized by coupling at least two lines (29) to a yoke (40) and mounting the yoke on the front end of the anchor body (11) and pulling up the yoke by pulling one of the lines to release the yoke from the anchor body when the anchor has been used. 8. A method according to claim 7, characterized by mounting three lines (29) to the yoke (40), 9. A method according to any one of the preceding claims, characterized by hammering down the anchor body (11) by hammering on the rod (17) which is an extension rod, for example a conventional rock drill extension rod. 10. An inflatable soil anchor body (11) made of folded sheet metal that is sealed in both ends and has an inlet (18) for pressure fluid at its rear end, characterized by a bow-formed support (22) for a steel rope (29) at its front end, said support permitting the rope to slide therein.

Inventors: SKOGBERG BO TORBJOERN, SKOGBERG, BO, TORBJOERN
Applicants: SOILEX AB
Application year: 1992
Main classification: E02D5
IPC codes: E02D5