The invention is directed to a sealing device kit, a strand ground anchor and a method for sealing a strand ground anchor.

Strand ground anchors are commonly used to mechanically fix a certain structure such as a retaining wall or foundation to the ground. Those strand ground anchors have to withstand high ten sile forces and have to fix the structure safely for a long time to the ground. Strand ground anchors are typically installed in ground conditions which vary in terms of density, porosity, wa ter level and environmental aggressivity. Visual monitoring is impossible as the installed anchor is invisible. Therefore, cor rosion protection of a ground anchor is crucial to achieve the desired performance. Especially in the transition zone, the part of anchor tendon in the ground adjacent to the anchor head, the coverage of the steel strand ends and the bare strand surface is exposed directly to the aggressive environment in the ground. This leads to a high risk of corrosion in the transition zone.

There are current protection solutions for the transition zone, but they either lack a reliable performance or are very complex and costly. Usually, a double-layer corrosion protection is re quired for permanent strand ground anchors.

The outer layer of corrosion protection in the transition zone is usually composed by a steel recess pipe, a protection duct in the free length and the sealing connection in between. Double 0- rings are widely used for this sealing connection. O-rings can be preinstalled onto the protection duct at predefined positions and then the recess pipe can be installed. However, during in stallation of the recess pipe it is highly possible that the o- rings are pushed away from the initial position and stay outside of the recess pipe. To avoid this, the O-rings or other sealing rings could be installed within the recess pipe. Nevertheless, this leads to the need of an additional steel ring to be welded inside the recess pipe for pushing the ring forward over the protection duct. This solution is expensive and difficult due to the friction especially in big size strand anchors.

The sealing function of the O-rings is only given if they are compressed and deformed evenly. Therefore, the tolerance range of the geometry on the onside positioning of all the related components is very limited. As relative angular or axial dis placement between recess pipe and protection duct often occurs in the construction site, the sealing performance is signifi cantly reduced.

The inner layer of corrosion protection in the transition zone usually comprises corrosion protection compounds like grease or cement/resin grout, which are used to fill the space of the transition zone in which the bare strand surface is exposed.

This protection of the strands has the disadvantage that the grease will drop down by its own weight over time. When a hard ened material like cement grout is used, the hardened materials are in high risk of getting cracked when the strands need to be restressed for anchor force controlling or adjusting. Hence, this corrosion protection is not durable.

It is therefore an object of the present invention to improve the solutions of the prior art and in particular provide a seal ing device kit, a strand ground anchor and a corresponding meth od for sealing a strand ground anchor which are durable and easy to install. The object is achieved by a sealing device kit, a strand ground anchor and a method for sealing a strand ground anchor according to the independent claims.

The object is in particular achieved by a sealing device kit for protection of strand ground anchors comprising at least one, transition pipe kit and/or a bellow sleeve kit.

The transition pipe kit is the sealing device kit for sealing the inner layer of corrosion protection, while the bellow sleeve kit is the sealing device kit for sealing the outer layer of corrosion protection. The complete sealing device kit leads to the desired double layer corrosion protection of the strand ground anchor.

The transition pipe kit is designed such that it protects an ar ea of a strand of the strand ground anchor substantially at an anchor head area, in particular between the anchor head and a sheath of the strand. The bellow sleeve kit is designed such that it protects the transition area of the strand ground an chor.

The transition pipe kit comprises a transition pipe and an annu lar plug sleeve. The annular plug sleeve is connectable to, in particular connected to, a sheath of a strand and to the transi tion pipe. The annular plug sleeve is arrangable, in particular arranged, substantially concentrically to the strand, wherein the transition pipe is connectable, in particular connected to, the anchor head and to the annular plug sleeve. The transition pipe is arrangable, in particular arranged, substantially con centrically to the strand. The annular plug sleeve is arrangable between the transition pipe and the strand. The annular plug sleeve is arranged concentrically inside the transition pipe. The transition pipe comprises a first end area having a first inner diameter and a second end area having a second inner diam eter. The first inner diameter is different from the second in ner diameter.

The bellow sleeve kit comprises the bellow sleeve, an upper fix ation and a lower fixation. The bellow sleeve comprises, in par ticular consists of, an elastic material, preferably having a Young's modulus less than 10 MPa and/or an elongation at failure of more than 50%. The upper fixation is connectable, in particu lar connected, to an envelope of the transition zone, preferably to a protective element, in particular a recess pipe, a retain ing structure and/or a load transfer element, in particular a bearing plate, of the strand ground anchor. The lower fixation is connectable, in particular connected to, a protection ele ment, in particular a protection duct, of the strand ground an chor.

Such a sealing device kit comprising a transition part kit and/or a bellow sleeve kit leads to an easy, safe and durable double layer protection of the strands against corrosion.

In a strand ground anchor there is one transition pipe kit seal ing one strand, while there is one bellow sleeve kit sealing several strands. By means of the transition pipe kit the area of the bare strands at the anchor head is protected while the bel low sleeve kit comprises a protection for the transition zone, in particular between a protective element such as the recess pipe and the protection duct. The complete sealing device kit provides a complete protection of the strand ground anchor at its corrosion sensitive points. The first end area of the transition pipe can be connectable, in particular connected, to the anchor head and the second end area of the transition pipe can be at least partially connectable, in particular connected, to the annular plug sleeve, wherein the first diameter in the first end area is smaller than the second diameter in the second end area.

Preferably, the connection between anchor head and transition pipe is a press fit connection.

This way the transition pipe kit can be securely fastened to the anchor head in a way that the transition pipe is arranged be tween the anchor head and the strand. Further, the transition pipe can be safely arranged onto the annular plug sleeve and lead to a secure protection of the strand in the area between anchor head and sheath of the strand.

Preferably, the transition pipe is a pipe having a circular or substantially circular cross section. Similarly, preferably the annular plug sleeve has a circular or substantially circular cross section.

The first end area of the transition pipe can comprise at least one, preferably two, ribs on the outer surface of the transition pipe, wherein the shape of the rib or the ribs in cross section can be triangular.

Those ribs facilitate the insertion of the transition pipe into the hole in the anchor head. Additionally, the retraction of the transition pipe from the anchor head is inhibited. The first end area can comprise a flange on the outside of the transition pipe, wherein the shape of the flange preferably sub stantially corresponds to the shape of the second end area or the flange has a shape which is adapted to fit to the shape of the anchor head. Preferable, the flange comprises a circular section.

This flange leads to keeping the transition pipe in the appro priate position and stabilizes the transition pipe.

The shape of the second end area can be any shape in particular circular ellipsoid, triangular, quadrilateral, square.

The second end area of the transition pipe can comprise an inner surface which is chamfered.

Such a chamfered inner surface facilitates the insertion of the plug sleeve into the transition pipe and thereby leads to an easier installation.

The transition pipe can comprise a holding element for holding a distance plate on the outside of the transition pipe in the sec ond end area.

Such a holding element enables stabilisation of the transition pipe in the ground anchor.

The annular plug sleeve can be made from elastic material, in particular from rubber, such as NR, NBR, EPDM, SDR or Butyl.

Other materials could be silicon, polyurethane or other artifi cial elastomers. This enables a safe sealing which is durable and easy to in stall.

The annular plug sleeve can comprise a strand connection area and a sheath connection area, wherein the inner diameter of the strand connection area is smaller than the inner diameter of the sheath connection area.

This enables a perfect fit of the annular plug sleeve onto the strand, in the area where the sheath begins.

The annular plug sleeve can comprise internal ribs on the inside surface of the annular plug sleeve in the sheath area.

The sheath area of the annular plug sleeve can have a constant inner diameter or can have a conical shape with an increasing inner and/or external diameter.

This enables the adaption of the annular plug sleeve to the sit uation needed.

The annular plug sleeve can further have ribs on the outside of the surface of the annular plug sleeve in the sheath area.They prevent extraction of the annular plug sleeve from the transi tion pipe.

The transition pipe is preferably made from plastic material to avoid any damage on the anchor head and the prestressing strands.

The bellow sleeve can be at least partly corrugated. This corrugation enables the elongation and the reduction of the lengths of the bellow sleeve according to the needs of the strand ground anchor. The corrugation can be arranged in the middle of the bellow sleeve while the ends are corrugation free, in particular flat surfaces according to the shape of the pro tective element, in particular the recess pipe or the protective duct respectively. The upper fixation is preferably arranged in a flat area and the lower fixation is preferably arranged in a second flat area.

The fixation can be a mechanical fixation such as a ring clamp or strap. Additionally or alternatively the fixation can be a chemical fixation such as glue or melting etc.

This enables an easy fixation of the bellow sleeve kit to the strand ground anchor.

The corrugation and the material characteristics for the bellow sleeve kit can be chosen such that an axial displacement from a neutral position of the bellow sleeve from minus 2000mm to posi tive 2000mm is possible.

This range enables a movement within the strand ground anchor which occurs frequently. Nevertheless the sealing function of the outer layer sealing is still guaranteed.

The object is also achieved by a strand ground anchor comprising at least one strand having a sheath, a protection pipe, such as a recess pipe, and a protection duct. The strand ground anchor comprises a sealing device kit as previously described. The strand ground anchor can comprise two strands having a sheath each, wherein between both transition pipes a distance plate is connected to both transition pipes at the holding ele ment.

The strand ground anchor can further comprise at least one of the following an anchoring element such as an anchor head and a load bearing element such as a bearing plate and grout.

For corrosion protection the strand ground anchor can comprise at least one of the following a PE sheath and end cap on the protection duct and sealing devices or components at each joint and protection cap at the anchor head and flexible filling mate rials for corrosion protection.

The object is further achieved by a method for sealing a strand ground anchor, the method comprising the steps of installing at least one transition pipe kit and/ or a bellow sleeve kit as previously described on a strand ground anchor.

Preferably, the annular plug sleeve is arranged coaxially on a strand at a point where a sheath of the strand ends. The transi tion pipe is arranged coaxially to the annular plug sleeve and the strand.

The bellow sleeve kit is fastened to a protection duct using the lower fixation and the upper fixation is connected to a part of the envelope of the transition zone.

The invention is further described in embodiments by means of figures in the following: Figure 1: A cross section through a strand ground anchor including a sealing device kit according to the invention,

Figure 2: a bellow sleeve as shown in Fig. 1,

Figure 3: a strand ground anchor according to the invention comprising a bellow sleeve kit in an extended po sition,

Figure 4: a cross section through a strand ground anchor comprising a bellow sleeve kit in a compressed state,

Figure 5: a cross section through a transition pipe kit on a strand,

Figure 1 shows a cross section through a strand ground anchor A comprising a sealing device kit for the protection of the strands 1 against corrosion. To achieve this goal the strand ground anchor A comprises two transition pipe kits 5 and one bellow sleeve kit 8. One transition pipe kit 5 is arranged on each strand 1. Each transition pipe kit 5 comprises a transition pipe 51 and an annular plug sleeve 52. The strands 1 are covered by a sheath 7 made from PE. The end of the sheath 7 is covered by annular plug sleeve 52, such that the annular plug sleeve 52 covers a part of the sheath 7 and a part of the bare strand 1. For this, the annular plug sleeve 52 comprises a strand connec tion area 521 (see Fig. 5) and a sheath connection area 522 (see Fig. 5). The inner diameter of the strand connection area 521 is smaller than the inner diameter of the sheath connection area 522. The transition pipe 51 concentrically surrounds the annular plug sleeve 52 and the strand 1. The transition pipe 51 is con nected to the anchor head 2 in the first end area 53 of the transition pipe 51 and to the annular plug sleeve 52 in the sec ond end area 55. The inner diameter of the first end area 53 is smaller than the inner diameter of the second end area 55. The first end area 53 of transition pipe 51 comprises a flange 512. The flange 512 is arranged below the anchor head 2 and without touching a bearing plate 3. The bearing plate 3 has a load dis tribution function and can also be substituted by other load distribution elements known in the state of the art. The transi tion pipe 51 is arranged in a hole 21 in the anchor head 2 by a press fit connection. The second end area 55 of the transition pipe 51 comprises a holding element 514 for holding a distance plate on the outside of the transition pipe 51.

The bellow sleeve kit 8 comprises a bellow sleeve 81, which is corrugated in a middle area in view of a longitudinal centre ax is of the bellow sleeve 81 and has two flat ends. The first flat end comprises an upper fixation 82 which connects the bellow sleeve 81 to a recess pipe 4. The second flat end area comprises a lower fixation 83 which connects the bellow sleeve 81 to pro tection duct 9. The corrugated area of the bellow sleeve 81 leads to a tight sealing even in case the recess pipe 4 moves relative to the protection duct 9. The bellow sleeve 81 consists of an elastic material having a Young's modulus of less than 10 MPa and/or an elongation at failure of more than 50%. The upper and the lower fixation 82, 83 are ring clamps.

Figure 2 shows the bellow sleeve 81 in a neutral position.

Figure 3 shows only the bellow sleeve kit 8. In this state the bellow sleeve 81 is extended such that the strands are still covered by the bellow sleeve even if the recess pipe 4 and the protection duct 9 were moved away from each other. All other features of the bellow sleeve kit 8 correspond to the features of figure 1.

Figure 4 shows the bellow sleeve kit 8 in a compressed position. In this position the corrugated part of bellow sleeve 81 is com pressed but still ensures the sealing function between recess pipe 4 and protection duct 9. All other features of bellow sleeve kit 8 correspond to figure 1.

Figure 5 shows the annular plug sleeve 52 as shown in figure 5 installed on a strand 1 including the transition pipe 51. This installation situation corresponds to the installation shown in figure 1. The transition pipe 51 comprises protruded ribs 511 to connect to the anchor head as shown in figure 1. The part of the transition pipe 51 that is introduced into the anchor head 2 is ended with flange 512. This enables a perfect fixation of the transition pipe and the anchor head at the right position. The inner diameter of the transition pipe 51 in the area introduced into the anchor head 2 is smaller than the inner diameter on the other end of the transition pipe 1 where the annular plug sleeve 52 is arranged inside the transition pipe 1. Between the smaller inner diameter at the anchor head side and the broader inner di ameter in the annular plug sleeve area there is a conical zone 513. The transition pipe 51 encloses the annular plug sleeve 52 completely and both are arranged concentrically to the strand 1. The transition pipe 51 comprises a groove 514 to position a dis tancing plate between several transition pipes 51. The end of the transition pipe 51 in the area where the groove is arranged is chamfered on the inside to facilitate introduction of the an nular plug sleeve into the transition pipe 51. The material of the transition pipe 51 is harder than the mate rial of the annular plug sleeve 52. This leads to an optimal sealing effect. Several of the transition pipes 51 and annular plug sleeve 52 are arranged in one strand ground anchor as shown in figure 1 where each strand 1 of the strand ground anchor A comprises one transition pipe kit 5.