The invention relates to a method for introducing a ground anchor into the ground, comprising the step of screwing an elongate anchor body into the ground by means of an extension rod that is to be connected to the proximal end of said anchor body.

Such a method is well-known and is applied e.g. for stabilizing permanent or temporary sheet-pile walls that are driven into the ground at a distance from the anchor body. In a frequently and succesfully applied embodiment of the well-known method an anchor body having a hollow core and screw blades is used and after this anchor body has been screwed into the ground a settable mortar is intro¬ duced. The mortar is pressed through the extension tube and the hollow space of the anchor body into the earth between the screw blade turns to form together with said earth a solid mass, in which the anchor body becomes fixedly anchored.

The extension tubes form a permanent part of the anchor and are attached to the sheet-pile wall with the proximal end extending through a hole in the sheet-pile wall and with the intermediary of an anchoring support.

In general the introduction of the ground anchors into the ground is started only after the sheet-pile wall is completed. For the introduction of the individual sheet- piles involves powerfull vibrations, which are transmitted through the earth. If one would start the introduction of the ground anchors, while continuing driving or vibrating further sheet-piles into the ground, these vibrations would prevent an effective setting process of the settable mor¬ tar, so that the required resistance to pull out would not be obtained.

It is an object of the invention to improve the well- known method in the sence, that the introduction of the

ground anchors may be started without objection already before the structure to be stabilized (i.e. sheet-pile wall) has been completed, and if desired immediately upon the introduction of each next sheet-pile or group of sheet- piles, so that the overall time required for driving con¬ structions, such as sheet-pile walls, into the ground and anchoring the same, may be substantially reduced.

According to the invention this aim is achieved in that the distal end of a line of sufficient tensile strength is connected to the anchor body at a location that is posi¬ tioned between the two ends of the anchor body and excen- trically relative to the cross section of the latter, said line extending through the connected extension tube out¬ wardly, said extension tube being unscrewed from the anchor body after the latter having arrived at the desired depth, a pull load being then applied to the free proximal end of said line remaining connected to the anchor body, the intensity of the pull load being such that it causes the anchor body to perform a turning movement through the ground about the attachment point of said line, after which movement the proximal end of said line is attached to the structure to be stabilized.

By causing the anchor body to turn under the influence of the pull load exerted at the proximal end of the line, the axis of the anchor body will become positioned at an angle relative to the line, so that the resistance to a pull out is increased. 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.

The use of a settable mortar, as with the well-known method above referred to, is omitted and this fulfills the condition under which it is allowed to place the anchors each time immediately after the last sheet-pile is driven into the ground.

By placing a ground anchor into the ground at the

location of each sheet-pile use can be made of ground anchors having a relatively low tensile strength, while it is no longer required to place supporting beams along the outer side of the sheet-pile wall, as is required when using ground anchors at a mutual spacing that is many times larger than the width of a sheet-pile.

The invention also relates to a ground anchor to be used with the above method, said ground anchor comprising an elongate anchor body, having a core rod with two or more screw blades, said rod having its proximal end removably connected, by means of a coupling sleeve, to the distal end of an extension tube, such an anchor being known per se.

The ground anchor according to the invention is charac¬ terized by a pulling line extending along the core rod of the anchor body, said line having its distal end anchored to the core rod at a location within a central area of said rod, said line extendings fire said coupling sleave into the extension tube and through the proximal end of the latter outwardly, the screw blade extending from said core rod being slitted according to a plane substantially going through the axis of the anchor body, such that after removal of the extension tube the line may swingabout its anchoring location and through the slit(s) outwardly.

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 a 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 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 (posi¬ tioned 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 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 thick¬ ening 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 periphery 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 sleave 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 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 anchor¬ ing 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 inwardly beveled at its distal end 5a in a direction B, which promotes the turning movement of the anchor body 1 in the arrow direction.