A method for applying a ground anchor into the ground, and anchor to be used therewith

Abstract: A method for introducing a ground anchor into the ground, comprising the step of screwing an elongate anchor body (1) into the ground by means of an extension rod (6) that is to be connected to the proximal end of said anchor body (1). The distal end of a pull line (8) is connected to the anchor body (1) at a location that is positioned between the two ends of the anchor body and excentrically relative to the cross section of the latter. Said line (8) extends through the connected extension tube (6) outwardly. The extension tube (6) is unscrewed from the anchor body (1) after the latter having arrived at the desired depth. A pull load is then applied to the free proximal end of the pull line (8), said load being large enough to cause the anchor body (1) to turn through the ground about the attachment point of the pull line, after which the proximal end of the line is attached to the structure to be stabilized.

Description: The invention relates to a method as defined in the first part of claim 1. Such a method is disclosed in document US-A-2 603 319. With this well-known method the anchoring line is secured with its distal end to an eyelet that laterally extends from a bushing which is rotatably mounted around a screwblade free portion of the core rod of the anchor body. When in the process of screwing the anchor into the ground the anchor has been lowered to the extent the desired fastening location of the bushing is about to enter the ground, the bushing is placed and the anchoring line is fastened. The lowering (by screwing) of the anchor may then be continued and one or more extension tubes are connected when necessary. During continued lowering of the anchor the bushing is allowed to swivel about the rotating core rod and the anchoring line cuts its way through the ground downwards. As soon as the distal end of the anchor has reached the desired depth the method is, in fact, completed and the anchoring line extends alongside the anchor body and the extension tubes, if any, and through the ground upwards. There is no mention of disconnecting an extension tube after the anchor body has arrived at the desired depth. The method according to the present invention distinguishes from the well-known method by the features defined in the second part of claim 1. By causing the anchor body to tilt under the influence of the pull force exerted at the proximal end of the anchoring line - after the extension tube(s) have (has) been removed - the axis of the anchor body will become positioned at an angle relative to the line and this gives an increase of the resistance to pull out. The ultimate resistance to pull out of the anchor body will be the higher, the more the pull load on the line is increased and thus the angle between the axis of the anchor body and the line will become larger. It is to be noted that DE-U-85 19 054 discloses a method, whereby an elongate anchor body is introduced into the ground by connecting one end of it to the distal end of an extension rod and applying hammerblows onto the proximal end of the extension rod. An anchoring line extends alongside the anchor extension tube assembly and is fastened with its distal end to the anchor body at a pivot point that is positioned about midway between the ends of the anchor body. Upon hammering the extension rod is removed by unscrewing. Thereupon it is envisaged to cause the anchor to tilt about the fastening point by pulling at the proximal end of the line. The invention also relates to a ground anchor as defined in the first part of claim 2. The improved anchor according to the present invention is characterized by the features defined in the second part of claim 2. The invention will be hereinafter further explained by way of example with reference to the drawing. Fig. 1 is a side view of an anchor according to the invention, in a position under an elevational angle α, that is taken by the anchor body relative to the horizontal plain during its introduction into the ground; fig. 2 is a side view of the anchor of fig. 1, after the anchor body having arrived at the desired depth, the extension tube is unscrewed and removed and a pulling force has been exerted onto the permanent anchoring line and fig. 3 is a cross-sectional view at a larger scale, along the line III-III of fig. 1. The anchor shown in fig. 1 of the drawing has to be driven into the ground under an elevational angle α e.g. 25-40°. It comprises an anchor body 1 in the form of a core rod 2 that is provided with a screw blade 3 in a well-known manner and ends at its distal end into a beveled frog 4. A longitudinal recess 7 is provided in the surface of the core rod 2 to accomodate a steel wire cable 8. The longitudinal recess 7 extends through a part of the length of the core rod, vz. from the proximal end of it (positioned within the coupling sleeve) up to a location X at the cross sectional plane III-III. From the location X the longitudinal recess 7 continues in the form of a passage 7a that extends through and obliquely to the opposite longitudinal side of the core rod 2. The distal end portion of the cable 8, that bends inwardly through said passage 7a, is anchored in the widened end 7b of the passage 7a, e.g. by means of a thickening 9 swaged on the distal end of it. The screw blade 3 is interrupted at the longitudinal recess 7 by radially outwardly extending slits 10, which communicate with said recess and merge into the peripheral edge of the screw blade 3. The coupling sleeve 5 is provided with a longitudinal slit 11 that corresponds with the longitudinal recess 7. In the situation shown in fig. 1 the cable 8 is locked in place within the longitudinal recess 7 and within the extension tube 6 screwed into the coupling sleeve 5 respectively. The cable leaves the extension tube 6 at the proximal end (not shown in the drawing) of said extension tube. In this state the anchor is driven in a well-known manner, under the desired elevational angle α into the ground by rotating it in the arrow direction A. After the ground anchor has arrived at the desired depths, the extension rod 6 is unscrewed by rotating it in a direction opposite to the arrow A, and then pulled out of the ground, after which a pulling load is applied at the proximal end of the steel wire cable 8 (see fig. 2) under the influence of which the anchor body 1 is turned about the anchoring location X in the arrow direction B, while allowing the cable 8 to move out of its seat 7 and through the longitudinal slit 11 and the radial slits 10 outwardly. As explained herein above, the ultimate resistance to pull out of the anchor body will become higher, as the pull load on the steel wire cable (functioning as a permanent anchoring line) is increased and thereby the angle β between the axis of the anchor body 1 and the line 8 will increase. As shown in the drawing yet, the coupling sleeve 5 may be beveled at its proximal end 5a, as seen rearwardly and opposite to the direction B. This facilitates the tilting movement of the anchor body 1 in the arrow direction.

Claims: A method of introducing an elongate ground anchor body (1), comprising a core portion (2) and a screw blade portion (3) thereon, into the ground, said method comprising the steps of screwing the elongate anchor body (1) into the ground by making use of an extension tube (6) that is connected to the proximal end of said anchor body (1) and then rotated until the anchor body (1) has reached a desired depth, fastening an anchor line (8) of sufficient tensile strength with its distal end to the anchor body (1) at a location (X) that is positioned excentrically relative to the cross-section of the anchor body (1) and at an intermediate point of the length of the latter, said line (8) being held to extend from said fastening location (X) upwardly alongside the proximal portion of the anchor body (1) and further upwardly while screwing the anchor body down, characterized by the additional steps of causing the anchoring line (8) to extend from said location (X) in a position alongside the core portion (2) of the anchor body (1) towards the proximal end of the anchor body (1) and from the latter end into and through the extension tube (6) connected thereto, unscrewing the extension tube (6) from the anchor body (1) and removing it from said anchoring line (8) after the anchor body has arrived at the desired depth, applying a pull load to the free proximal end of the anchoring line (8) which is large enough to enable the anchoring line (8) to escape from said alongside position through radial slits (10), provided in said screw blade portion at said alongside position and thereby to cause said anchor body (1) to perform a tilting movement through the ground around said fastening location (X), after which movement the proximal end of said anchor line is attached to the structure to be anchored. A ground anchor for use with the method of claim 1, comprising an elongate anchor body (1) having a core rod (2) provided with two or more screw blades (3), an extension tube (6), having its distal end removably connected, by means of a coupling sleeve (5), with the proximal end of the core rod (2) of the anchor body (1), an anchoring line (8) having its distal end secured to the anchor body (1) at a location (X) that is positioned excentrically relative to the cross section of the anchor body (1) and at an intermediate point of the length of the latter, characterized in that said anchoring line (8) extends from said securing location (X) first alongside the core rod (2) of the anchor body (1) towards the proximal end of the latter and then from the proximal end of the core rod (2) into and through the extension tube (6), that the connection between the said core rod (2) and said extension tube (6) is a threaded sleeve (5) connection and that the screw blade(s) located on the core rod length between said securing location (X) and the proximal end of the core rod (2) is (are) radially outwardly slotted in a plane that substantially goes through the axis of the anchor body (1) and through said securing location (X), such that unscrewing and removal of said extension tube (6) enables said anchoring line to escape through the radial slits (10) of the screw blade(s) (3) outwardly and thereby allow the anchor body (1) to tilt about said securing location (X) relative to said line (8). A ground anchor according to claim 2, characterized in that a longitudinal recess is provided in the surface of the core rod, said recess extending from the proximal end of the latter up to said securing location and serving as a seat for the said line. A ground anchor according to claim 3, characterized in that the longitudinal recess (7) continues at the securing location (X) in the form of a passage (7a) that extends obliquely through and towards the opposite side of the core rod, where the distal end of the line is anchored in the free and widened end (7b) of said passage (7a). A ground anchor according to claims 2-4, characterized in that the slits (10) in the screw blades (3) have an outwardly increasing width. A ground anchor according to claims 2-5, characterized in that the coupling sleeve (5) is permanently attached to the proximal end of the core rod (2) and is provided with a longitudinal slit (11) in alignment with the recess (seat) (7) for the said line (8) along the core rod (2). A ground anchor according to claim 6, characterized by the proximal end (5a) of the coupling sleeve (5) being beveled.

Inventors: VAN HALTEREN TIJMEN, VAN HALTEREN, TIJMEN
Applicants: HALTEREN TIJMEN VAN, VAN HALTEREN, TIJMEN
Application year: 1996
Main classification: E02D5
IPC codes: E02D5