Shuttering element for a trench wall and method for producing the trench wall

The invention relates to a shuttering element for a trench wall and to a method for producing the trench wall. To form the trench wall in the ground a first trench is produced initially, which is filled with a hardenable mass for forming a first trench wall segment. After the production of the first trench and before a hardening of an infilled mass into the first trench wall segment a shuttering element is arranged on at least one front face of the first trench. The shuttering element has a board-shaped base body comprising a first shuttering surface and a second shuttering surface, between which a receiving bead is arranged which is recessed with respect to the two shuttering surfaces. In the receiving bead a sealing tape is arranged which extends along the base body. The receiving bead is covered by a cover element, wherein a receiving space is enclosed in which the sealing tape is arranged.

The invention relates to a shuttering element for a trench wall for arrangement between a first produced trench wall segment and an adjoining second trench wall segment yet to be produced, with a board-shaped base body having a shuttering side with a first shuttering surface and a second shuttering surface, between which a receiving bead is arranged which is recessed with respect to the two shuttering surfaces and in which a sealing tape is arranged that extends along the base body, in accordance with the preamble of claim1.

Furthermore, the invention relates to a method for producing a trench wall in the ground from several vertical trench wall segments arranged adjacent to each other, wherein initially a first trench is produced in the ground which is filled with a hardenable mass for forming a first trench wall segment, wherein after the production of the first trench and before a hardening of the mass into a first trench wall segment a shuttering element is arranged on at least one front face of the first trench, in accordance with the preamble of claim9.

For decades, trench walls have been produced in particular for securing construction pits. For this purpose individual trenches are introduced successively into the ground, which are each filled with a hardenable mass to form the trench wall. Since trench walls are often also used as cut-off walls against lateral water leakage in construction pits, the individual trench wall segments arranged adjacent to each other are required to abut in a tight manner.

In this connection, it is known that after the production of a first trench and the infilling of the hardenable mass a so-called shuttering element is arranged in a side area. The board-shaped shuttering element extends across the entire depth of the trench and provides a defined side surface of the hardening trench wall segment. At the same time, the shuttering element often also serves as an abutment or guide surface during the forming of the adjoining second trench for the adjoining trench wall segment.

From DE 90 01 679.3 U1 a shuttering element can be taken that has a sealing tape which extends along the board-shaped base body. The sealing tape projects towards the side of the first trench wall segment, whose side surface delimits the shuttering element. In this way, the sealing tape can be embedded tightly into the hardening first trench wall segment. Following the production and filling of the adjoining second trench, the shuttering element is detached and removed from the trench prior to a hardening into the second trench wall segment. The shuttering element is therefore also referred to as a stop-end element. Not yet hardened mass of the second trench wall segment can enter into the free space and thereby bring about a deep and compact connection to the first trench wall segment. From EP 1 983 111 A1 a shuttering element consisting of pre-fabricated concrete parts can be taken.

A generic shuttering element can be gathered from DE 20 2011 051 438 U1. This known shuttering element can be inserted into the trench together with the reinforcing cage that serves to strengthen the trench wall segment. Hence, this also remains in the trench wall, with the joint tape extending towards the side of the shuttering in the outward direction. In this arrangement there is the risk that during the insertion of the shuttering element into the trench or during the excavation of the adjoining trench the elastic, sensitive sealing tape is damaged or even destroyed. This can affect the leak-tightness of the trench wall and therefore the function as a cut-off wall.

From DE 36 34 906 A1 it is known a generic shuttering element, which is designed as a pre-fabricated concrete part. A joint tape is arranged in a longitudinal groove of the pre-fabricated concrete part and secured by a panel-shaped covering element. The covering element is displaceably supported in a longitudinal guide of the pre-fabricated concrete part and can be pulled out during the concreting process of the trench wall, whereby the joint tape is exposed.

From GB 2 315 803 A a metallic hollow chamber profile as a shuttering element for a trench wall is known. The shuttering element consists of a panel-shaped front face and a U-shaped rear plate which jointly form an interspace for a sealing tape. For exposing the sealing tape the whole shuttering element with front face and rear plate has to be pulled out of the trench. For an extractor tool along the front face two longitudinal guides are provided, the guiding surfaces of which are kept free by means of a replaceable filling cushion.

In DE 40 16 388 A1 a shuttering wall for embedding a joint tape between two concrete segments is known. The joint tape is clamped between two elements that are bent in an L-shaped manner, the L-shaped elements are connected together by means of a U-shaped clamp. For exposing the sealing tape the L-shaped elements and the U-shaped clamp have to be retracted.

For exposing the sealing tape laborious working steps are necessary, wherein elements contaminated with concrete and bentonite are incurred. Such elements have to be cleaned or disposed.

The invention is based on the object to provide a shuttering element and a method for producing a trench wall, with which a trench wall with a high degree of leak-tightness can be produced in an efficient and reliable manner.

With regard to the shuttering element the object is achieved in that the receiving bead is covered by a cover element, wherein a receiving space is enclosed, in which the sealing tape is arranged.

A first aspect of the invention therefore resides in the fact that the sensitive, elastic sealing tape, which is also referred to as a joint tape, is arranged in a protected receiving space that is covered by a cover element. In this way, the sealing tape, which can consist of an elastic material or a thin sheet metal, is protected during transport and insertion into the trench. By preference, the cover element can be removed after the production of the adjoining trench so that a hardenable mass, especially a concrete mass, can flow into the receiving space and surround the sealing tape. The cover element can be recessed or protruding with respect to the two shuttering surfaces which preferably lie in one plane. By preference, the cover element and the shuttering surface lie in one plane.

Basically, the cover element can be a rail or a profile made of plastic or metal which is removed in a separate work process. According to the invention it is preferred that the cover element is a film, a textile or a grid. After insertion into the trench, these thin cover elements can be selectively torn open, thus opening the receiving space. This can be realized by the trench wall device that produces the adjoining trench. The trench wall device can be a trench wall grab in particular. Basically, the use of a trench wall cutter is possible too. A grid can also stay in place, since the hardenable mass can flow in through the grid.

Especially good protection is achieved in accordance with the invention in that the receiving space is filled with a flowable or pourable filling material. Preferably, provision is made for the filling material to be a gel, granulated material, sand or gravel or a mixture thereof. The filling material ensures a secure coating of the sealing tape. Moreover, the filling material produces a counter-pressure in the receiving space so that even if the cover element is of very thin design the shuttering element can be inserted without difficulty into greater depths, as for example trench depths of 10 m and more. When the cover element is removed or torn open, the flowable or pourable filling material can flow into the adjoining second trench so that the sealing tape can be surrounded by the hardenable mass in the desired way. The outpouring filling material can be removed with the ground material during the production of the trench or it can be a component of the hardenable mass. The filling material can then be tuned to the hardenable mass in such a way that it fosters the solidity of the hardenable mass or at least does not reduce it on a permanent basis.

Another preferred embodiment of the invention resides in the fact that on a side edge of the first shuttering surface and the second shuttering surface a side wall section pointing rearwards from the shuttering side is arranged in each case. The shuttering element with the two shuttering surfaces has a width corresponding to the width of the produced trench. In order to prevent the hardenable concrete mass from penetrating from the rear side towards the outward pointing shuttering surface, rearward pointing side wall sections are arranged on the two outer side edges of the first shuttering surface and the second shuttering surface. These side wall sections prevent the coarse concrete mass from surrounding and thereby contaminating the shuttering surface or would make this much more difficult. Consequently, the shuttering surface can serve as a guide surface for guiding the trench wall device when the adjoining trench is produced.

Basically, the shuttering element can be designed as a stop-end element that is removed from the trench prior to the setting of the second trench wall segment.

In accordance with one design variant of the invention it is preferred that the base body has a fixing side which faces away from the shuttering side and on which the base body is fixed by way of connecting elements to a reinforcing element. The reinforcing element is part of the shuttering element, forming a unit with the latter. The connecting elements can, in particular, be metal struts, wires or a bridging grid, with which the base body made of sheet metal is fixed, in particular welded, to the reinforcing element consisting of metal. The connecting elements can serve at the same time as a bracing of the sheet metal base body, whose sheet thickness ranges between 1 mm and 5 mm. Hence, the shuttering element can be installed in the trench in one work process with a steel beam, a reinforcing cage or a differently designed reinforcing element. It remains in the trench as a so-called permanent shuttering element.

A preferred further development of the invention resides in the fact that the shuttering element is designed with a length that is greater than a length of the reinforcing element and corresponds to the depth of the trench wall. In particular, the shuttering element can protrude downwards with respect to the reinforcing element that serves to reinforce the trench wall segment. The shuttering element can thus serve for placement onto the bottom of the trench, without the reinforcing element itself coming into contact with the base of the trench. In this way, the reinforcing element can be arranged in a precise position within the hardening trench wall segment.

A further advantageous embodiment of the invention resides in the fact that the shuttering element is composed of several parts which are fixed at a defined distance to each other along the reinforcing element. The shuttering element can basically be arranged on only one or on both front faces of the reinforcing element. The shuttering element can be designed as a continuous board or it can be subdivided into parts. The parts can be butt-jointed or overlap. During transport of the shuttering element with the reinforcing element and the parts fixed thereon and especially during erection of the shuttering element from a horizontal transport position into a vertical installation position by means of a crane, prevention is thus made from permanent deformations occurring on the shuttering element during erection. In fact, the dividing joints serve as hinge points. The individual parts of the shuttering element which can each have a length ranging from one meter up to several meters will scarcely deform during erection in this arrangement.

The invention furthermore relates to a trench wall in the ground consisting of at least two vertical trench wall segments, wherein between the trench wall segments a shuttering element according to the invention is arranged. In particular, the trench wall is composed of a plurality of such vertical trench wall segments that adjoin side by side. In the area of the respective joint the shuttering element according to the invention is arranged, and in particular this is not extracted but remains in the trench wall and is thus solidly embedded in concrete.

The method according to the invention is characterized in that a shuttering element pursuant to the invention is inserted, wherein a receiving space around a sealing tape is enclosed on one shuttering side. Hence, as described above, the sealing tape can be protected up until installation and in this way provide a high leak-tightness of the trench wall.

A preferred method variant resides in the fact that after the insertion of the shuttering element with the shuttering side pointing outwards an adjoining second trench is produced for forming an adjoining second trench wall segment, wherein a cover element located on the shuttering element is torn open or removed in order to open the receiving space and expose the sealing tape. In the case of a thin cover element, such as a film, a geotextile or a grid, the tearing open can be brought about in the course of the normal operation of a trench wall device when this excavates the adjoining trench. In principle, however, it is also possible to provide a special mandrel or protrusion on the trench wall device, which approximates the cover element and purposefully tears it open or pulls it off.

According to a further method variant it is advantageous for the hardenable mass to flow from the adjoining second trench into the opened receiving space around the sealing tape, wherein the sealing tape seals a joint between the two adjoining trench wall segments.

In accordance with the invention, protection of the sealing tape can be improved further in that upon opening the receiving space filling material flows from the receiving space into the adjoining trench. The filling material, in particular sand, a granulated material, gravel or a gel, surrounds the sealing tape and in addition stabilizes the receiving space. After the cover element has been torn open, the filling material can be removed with the ground or it can mix with the inflowing hardenable mass. When using a grid, the filling material has a grain size that is larger than the openings of the grid.

In principle, the shuttering element can be inserted separately into the trench. It is particularly economical that the shuttering element is inserted into the first trench together with a reinforcing element, on which the shuttering element is fixed. Consequently, only one work process is necessary for the insertion of the reinforcing cage and the shuttering element. In addition, a work-intensive detachment and removal of the shuttering element from the trench can be dispensed with.

According toFIG. 1a shuttering element10with a base body12made of sheet steel is shown. In cross-section the shuttering element10has an approximately W-shaped design. On one shuttering side14a plane first shuttering surface21and a plane second shuttering surface22are arranged, between which a substantially U-shaped receiving bead20is designed that is recessed backwards with respect to the shuttering side14. At the base of the receiving bead20in its center area an elastic sealing tape18, also referred to as a joint tape, is supported. The sealing tape18extends through the base body12, protruding on the one hand with an inner sealing section17into a receiving space24of the receiving bead20and on the other hand with an outer sealing section19towards a fixing side16that faces away from the shuttering side14. The sealing tape18can also consist of several parts, in particular the inner sealing section17can be separate from the outer sealing section.

At the opening directed towards the shuttering side14the receiving space24is closed with a grid-like cover element30. The cover element30designed as a grid is arranged flush with the first shuttering surface21and the second shuttering surface22, lying in one plane with them. In the receiving space24thus closed, filter gravel is introduced as a filling material36. The filling material36surrounds and protects the sealing tape18in the receiving space24. At the front faces the receiving space24is closed by additional side cover elements not depicted here.

The outer sealing section19of the sealing tape18, which protrudes from the base body12towards the fixing side16, is encompassed by a holder arrangement32that is U-shaped in cross-section. Through this, the elastic sealing tape18is protected towards the fixing side16. Moreover, the open holder arrangement32connects the two halves of the substantially symmetrical base body12.

At the respective free side edges of the two shuttering surfaces21,22a side wall section28is arranged in each case that is designed to rest against a wall of a first trench3.

In accordance with the invention a first trench3is produced initially in a ground5. In the commonly used methods for producing trench walls according to the single-phase or two-phase-principle the trench3is filled up with a hardenable mass7, only outlined roughly. The hardenable mass7, which is, in particular, a concrete material, hardens into a first trench wall segment1. Before the hardening into the first trench wall segment1the shuttering element10according to the invention is inserted into the first trench3, in particular when it is not yet filled with hardening slurry according to the two-phase method.

In the illustrated embodiment the shuttering element10is welded by way of metallic connecting elements44to a reinforcing cage serving as a reinforcing element40made of a steel grid. In this way, the shuttering element10can be hoisted together with the reinforcing element40as one unit into the slurry or into the still soft hardenable mass7. In doing so, the shuttering side14rests on the ground5against a first front face of the trench3, where an adjoining second trench wall segment2is produced.

The shuttering element10has a width corresponding to the width of the trench3, with the side wall sections28extending away from the shuttering side14along the longitudinal walls of the trench3. In this way, the side wall sections28prevent the hardenable mass7from penetrating towards the shuttering side14of the shuttering element10. The still flowable, hardenable mass7in the first trench3can surround the reinforcing cage, the connecting elements44, the open holder arrangement32and thus also the sealing section19of the sealing tape18on the fixing side16. Due to the arranged cover element30and the filling material36the hardenable mass7is prevented from flowing from the first trench3into the receiving space24.

In order to produce an adjoining second trench wall segment2a second trench4can then be produced in the ground5using a trench wall grab in particular. In this process, the trench wall grab can be guided in particular along the shuttering side14of the shuttering element10. In a two-phase method the excavation of the second trench4is carried out by filling the excavated trench4with slurry. The flowable hardenable mass7later replaces the slurry.

During or after the sinking of the second trench4the grid-like cover element30can be torn open by the trench wall device. As a result, the filling material36is able to flow from the receiving space24into the second trench4. Hardenable mass7from the second trench4can enter into the tooth-shaped receiving space24. Through this, a positive interlocking of the first trench wall segment1with the second trench wall segment2is attained, with the hardenable mass7flowing around the inner sealing section17of the sealing tape18. In this manner, the concrete joint between the first trench wall segment1and the second trench wall segment2is sealed by the sealing tape18.

By analogy, a trench wall can now be designed through the production of further trench wall segments whilst using the shuttering element10according to the invention.

According to the side view ofFIG. 2the shuttering element10extends beyond the length of the reinforcing element40. The shuttering element10can be arranged on both front faces of the reinforcing element40. In the case of a one-sided arrangement according toFIG. 2an additional foot element can be arranged on the opposite side of the reinforcing element40, allowing the reinforcing element40to be placed horizontally onto the shuttering element10and the foot element at the bottom of a trench.

In the embodiment according toFIG. 2the shuttering element10is composed of four parts11that are arranged so as to rest against each other. The parts11are each connected by way of connecting elements44to the reinforcing element40.

When the reinforcing element40is erected with the shuttering element10from a horizontal transport position into a vertical installation position, with the direction of erection running in line with arrow P or out of the drawing plane, there is a risk of deformation of a continuous shuttering element10. Due to the fact that the shuttering element10is subdivided into parts11, defined hinge points are created at the dividing joints so that the parts11do not suffer deformation or, at most, to a minimum degree only. The parts11can adjoin each other with a straight joint, a stepped joint or by overlapping by a few centimeters. At the dividing joints a sealing agent can be arranged in each case. The sealing tape18which is not depicted can preferably extend without interruption across all parts11of the shuttering element10.