EP0048444A2 - Method and shuttering element for producing slit walls in the ground - Google Patents

Abstract

1. A method of making slot walls, wherein wall sections (6; 32; 38) which are contiguous at their front ends are cast successively and sealed by a vertically extending joint plate (15) for which purpose a slot section (8) each is excavated corresponding to the length of the wall section to be produced, a shuttering element (7) extending throughout the height of the slot wall, partly receiving the joint plate, and having at its front side which is directed into the slot section, projections (28) for mutual interlocking of the individual wall sections, is positioned vertically in the slot section at the end thereof, the slot section is provided with a cage-type reinforcement, concrete is introduced into the slot section, and the shuttering element is moved laterally away from the cast wall section and then lifted out in vertical direction, characterized in that minor portions of the concrete introduced by tremie means into the slot section are directed to the backside of the shuttering element such that all cavities (16) at the backside of the shuttering element are filled up, and in that, prior to moving the shuttering element away laterally and lifting it out vertically, the adjacent slot section is excavated and the concrete adhering to the backside of the shuttering element is removed.

Description

The invention relates to a method for producing diaphragm walls, in which wall sections adjoining one another on the end face are concreted in succession and sealed by a vertically running joint tape, preferably provided with a horizontal shoulder in the area of the base plate connection, for which purpose a slot section is excavated in the length of the wall section to be produced, a formwork element extending over the diaphragm wall height, partially receiving the joint tape, which on its front side facing the slot section has projections for interlocking the individual wall sections, is arranged vertically at the end of the slot section, the slot section is provided with a reinforcement cage, concrete in Contractor procedure is introduced into the slot section, the subsequent slot section is excavated on the back of the formwork element and the formwork element after the partially embedded nated joint tape is lifted vertically.

Such a method, in which the subsequent slot section is excavated before the formwork element is lifted out, is already known (US Pat. No. 3,464,665). Here, however, nothing is said about the method used when pouring the concrete or about the design of the joint tape in the area of the base plate connection. To hold the joint tape, two hoses are provided which extend through the formwork element and, when inflated, clamp the joint tape in its rear region within the formwork element. Before the formwork element is pulled, the pressure is released from the hoses, thereby releasing the joint tape.

The formwork element is pulled in the vertical direction, as is generally customary, for which purpose push-off cylinders act on the underside of a cross member which is fastened to the upper end of the formwork element projecting above the earth's surface. In addition, the formwork element tapers towards its lower end in order to facilitate vertical pulling. This vertical pulling, which can possibly be made easier in a known manner by using formwork removal means such as greases or oils applied to the formwork element, poses a danger to the joint tape and its correct arrangement. This proves the long relative movement between the formwork element and the released joint tape when pulling vertically in the direction of extension of both parts as particularly disadvantageous. If the joint tape adheres locally to the formwork element, the joint tape can easily tear, especially since penetration of concrete slurry along the joint tape into the formwork element cannot always be prevented despite the transverse flange provided on the joint tape, which is supposed to seal against the formwork element. In addition, the formwork elements can often no longer be pulled even after the above-mentioned auxiliary measures have been used after the concrete has more or less completely set, which is particularly the case with deep diaphragm walls is the case. For this reason, drawing may have to be started early, for example 3 to 4 hours after the start of the contractor procedure, which in the case of deep slots means a step-by-step drawing that begins before the relevant slot wall section is filled with concrete. It can be seen that pulling forces are already transferred to the joint tape before it is fixed in its upper areas in the more or less strongly set concrete. Here is another source for improper joint tape sealing.

The known method is also disadvantageous in other respects. Up to now, it has always been wanted to avoid the concrete or slurry from reaching the back of the formwork element during concreting. Accordingly, the formwork element was closely matched in its width to the slot thickness and, if necessary, the formwork element was made in two parts and spread apart by means of an inflatable tube and pressed firmly against the opposite walls of the slot (DE-OS 20 23 372). This not only creates a smaller contact surface between the formwork element and the concrete, which makes pulling easier, it also creates a considerable overpressure on the front of the formwork element during concreting, which is due to the high specific weight of the concrete, which is that which is usually used in the contractor process Bentonite suspension exceeds. The resulting forces acting on the formwork element in the sense of a deflection make a box-shaped stiffened formwork element necessary in order to avoid deflections and the resulting hindrances when the formwork element is subsequently pulled. Such a formwork element is naturally voluminous, heavy and unwieldy and also complex. This is particularly true when there is no transverse tension of the formwork element absorbing the bending forces within the slot, which is true for US Pat. No. 3,464,665.

There two different formwork elements are provided, namely a box-shaped formwork element with a corresponding thickness in the contact area on the diaphragm walls, which largely makes it impossible for the concrete to pass to the rear of the formwork element, and a narrow formwork element in the form of a plate, the inclined walls of which slant towards one another from the longitudinal edges project and end at a distance from each other to accommodate the joint tape. This formwork element, which is thin on its sides opposite the walls of the slot, has a trapezoidal cross section which corresponds to the toothed recess to be formed in the band section to be produced. Accordingly, the formwork element is less wide than the slot and only delimits the slot in a central area. Here, the freshly filled concrete can indeed laterally flow past the formwork element, without the latter is flexed more in the longitudinal direction, but the diaphragm wall portion made receive frontally no smooth finish as is to be required for a single _w andfreie slot wall without Erdei circuiting.

Accordingly, the invention has for its object to improve the above-mentioned method so that the risk of damage or displacement of the joint tape is largely eliminated from its intended sealing position, while a simple handy formwork element should be used at the same time.

This object is achieved in that the concrete introduced into the slot section for filling voids is also passed to the rear of the formwork element, that when or after the subsequent slot section is excavated, concrete adhering to the back of the formwork element is chiseled off and that the formwork element before it is lifted vertically from the manufactured wall section into the subsequent slot section into the side.

These measures according to the invention ensure a pressure compensation between the front and the back of the formwork element, so that it can be made compact and inexpensive, although it extends over the entire diaphragm wall thickness and thus ensures a clean connection to the adjacent wall section. The formwork element does not have to be pulled after a short time, but can be done, for example, 24 to 48 hours after concreting, which is also advantageous from an organizational point of view. The formwork element is still not lost and can be used again because on the one hand the back of the formwork element is chiseled free and therefore the adhesion to the concrete is limited to the front of the formwork element and on the other hand the formwork element is not pulled vertically but pushed off to the side, with the push-off force being targeted can be brought up to the height at which the formwork element has not yet detached. Existing concrete bridges also tear between the front and the back of the formwork element, which do not cause any problems due to the comparatively small thickness of the formwork element. The lateral pressing of the formwork element leads to a particularly short relative movement between the formwork element and the joint tape, so that the risk of tearing is low. Furthermore, the joint tape is fixed in its sealing position by the already largely set concrete, even with deep diaphragm walls over the entire length of the joint tape. The intended chiseling off of the concrete does not make the process much more difficult, since the access to the rear of the formwork element is provided in any case by lifting the subsequent slot section and since the adhering concrete can be chiseled off comparatively easily from the smooth back of the formwork element. For the rest, with a suitable soil condition, a chisel tool must also be used when excavating the subsequent slot section. Finally, it must also be taken into account that only limited amounts of concrete have to be chiseled off, since the formwork element is arranged at the end of the excavated slot and thus only outbreaks at the end face of the slot section are filled with concrete, into which the formwork element would otherwise be pressed with bending.

The concrete can be guided laterally around the formwork element to the rear, especially since breakouts can also be expected in the side walls of the excavated slot and a thin formwork element then offers no significant resistance to the flow around the concrete. However, in order to be able to use a formwork element which essentially closes off the diaphragm wall section and to be independent of any accidentalities caused by the respective geological formation, it makes sense to guide the concrete through the formwork element to the rear side thereof. In this way, connections can be made at predetermined longitudinal distances between the front and the back of the formwork element, the connection cross-sections being dimensioned such that the concrete bridges penetrating the formwork element tear when the formwork element is pushed away from the side with a predetermined amount of force.

The invention also relates to a formwork element for carrying out the method according to the invention, consisting of an elongate plate with a flat rear side and with two stiffening members provided on the front side of the plate and running essentially over the entire length of the plate, which have transverse outer surfaces inclined to one another and between them Form a receptacle for the part of the joint tape to be embedded in the adjoining wall section.

Such a formwork element is, as stated, already known (US Pat. No. 3,464,665), even if it is only of training a toothed recess in the diaphragm wall section and not to limit the diaphragm wall section over its entire thickness. Such a plate-shaped thin formwork element is particularly suitable for carrying out the method described above if its width is adapted to the diaphragm wall thickness.

According to the invention, this formwork element is designed such that the stiffening members also have outer surfaces which are inclined in the longitudinal direction. This measure is made possible by pressing the formwork element sideways before lifting it out. It not only leads to the fact that the adjoining wall sections are interlocked with one another in the vertical direction in addition to in the horizontal direction - which was previously only possible with concrete formwork elements remaining in the diaphragm wall (DE-OS 19 25 025) - in addition, in Interest in protecting the joint tape ensures that the formwork element must necessarily be pressed laterally to a predetermined extent, for example 20 cm, before it can be lifted vertically. A vertical pull in the usual way is thus excluded.

Further expedient designs of the formwork element result from the subclaims. The meaning of these measures already largely results from the above explanations. In addition to the push-off surfaces at the front end of the formwork element, reference is made to two different possibilities for pushing the formwork element sideways. Lifting cylinders which can be extended and retracted can be integrated into the formwork element with longitudinal distances of, for example, 3 to 4 m and can be extended to an extent of, for example, 20 cm required for lateral pressing. In the interest of a formwork element that is as simple as possible, it is also possible to work with a separate press cushion, which from above is between the Formwork element to be pushed in and the concrete wall section inserted and lowered to the uppermost adhesion point between the two parts and then, for example, pressurized to separate the formwork element from the wall section. The push-off surfaces on the formwork element are advantageous here.

The method according to the invention and two different embodiments of the formwork element according to the invention are explained in more detail below on the basis of a schematic drawing.

Figures 1 to 3 each show stages in the plan view (top) and in a vertical longitudinal section (bottom) with a shortened slot length in the manufacture of a subsequent slot wall section.

4 to 7 show the first embodiment of the formwork element in a front view and a side view, in each case a central region of the formwork element being omitted, and in the two sections VI-VI and VII-VII made clear in FIG. 4.

Fig. 8 shows a perspective view, also with the omission of the central area, the end face of the wall section produced, the partially broken joint tape including the molded shoulder in the area of the lower sole plate is also shown.

Fig. 9 shows a perspective view of the joint between two adjoining vand sections with the joint tape.

Figures 10 to 13 show the second embodiment of the formwork element, again in front view, side view and in two characteristic sections indicated in Fig. 10.

Figures 1 to 3 illustrate the operation in the manufacture of a diaphragm wall section. For this purpose, guide walls 1 and 2 are set in a known manner, which protrude, for example, approximately 1.5 m deep into the ground and determine the width of the slot to be excavated and thus the slot wall thickness. The arrangement of the upper edge 3 of the guide walls 1 and 2 in alignment with the surface 4 of the soil 5 can be seen from the figures.

Fig. 1 is based on a concrete wall section 6 with a not yet drawn or raised formwork element 7. First, on the back of the formwork element 7, which is the right side of the formwork element in FIGS. 1 to 3, a subsequent slot section 8 is excavated in a known manner. Then, as indicated in FIG. 1, the back of the formwork element is cleaned by lowering a tool 10 with chisels 11, which is already known for crushing the earth material to be excavated, into the slot section 8. This tool 10 has been equipped with toothed strips 12 which chisel off the concrete 13 adhering to the rear of the formwork element 7. The tool 10 is provided with an inclined run-up surface 14 which, in accordance with the force decomposition indicated by arrows, ensures that the toothed strips 12 are pressed against the smooth rear side of the formwork element 7.

After cleaning the back of the formwork element 7, this is pressed laterally into the slot section 8, as indicated in FIG. 2, which can be done in the manner described above and is not indicated in more detail. Here, the formwork element 7 detaches from the joint tape 15 previously received in it, which, as indicated, is approximately half embedded in the wall section 6 that has already been produced. After the lateral pressing, the formwork element 7 is lifted out of the slot section 8.

Thereupon, the mold member 7 is provided with a new joint tape 15 'and corresponding to FIG. 3 on the loading placed the _re its concrete wall portion 6 facing away from the end of the slit section 8. Then a reinforcement cage is arranged in the slot section 8 in a known manner, whereupon it is filled with concrete in the contractor process. This concrete penetrates through the formwork element 7 or past its narrow longitudinal edges into the cavities 16 indicated in FIG. 3 on the back of the formwork element, as a result of which the concrete 13 shown in FIG. 1 and later demolished is formed.

The subsequent slot section is then excavated and the process is repeated with the steps described above.

The formwork element according to Figures 4 to 7 consists of an elongated plate 21, from the front of which two stiffening rails 22 protrude, which extend parallel to one another, form a slot-shaped receptacle 23 for the joint tape 15 and have end faces 24 which are inclined in the longitudinal direction. 7, the stiffening rails 22 are designed as a hollow profile with an inner leg 25 running perpendicular to the plate 21 and an inclined outer leg 26. The parts 21, 24, 25 and 26 are welded together. The end faces 24 and the outer legs 26 lead to a shape of the stiffening rails 22 that is conical in both the longitudinal and transverse directions.

On the outside of the stiffening rails 22, openings 27 are provided in the plate 21 at regular intervals in the longitudinal direction, which taper from the front to the rear of the plate 21.

Furthermore, 22 projections 28 are arranged on the outside of each stiffening rail, which in the transverse direction have inclined outer surfaces 29 and additionally inclined outer surfaces 30 in the longitudinal direction, which are each formed by welded sheet metal pieces and delimit closed cavities. The projections 28 are arranged in pairs next to one another and distributed over the length of the plate 21. The projections 28 are each arranged in the middle between the openings 27, which are likewise provided in pairs.

FIG. 8 shows a finished wall section 32 made of concrete, which is also referred to as a lamella, and reveals the toothing recesses 33 which originate from the projections ₂ 8 of the formwork element. The stiffening rails 22 have also created a recess 34. Furthermore, the joint tape 15 can be seen, the freely projecting section 36 was received in the slot-shaped receptacle 23 of the formwork element. Also shown in the area of the not shown sole plate on the joint tape 15 is the projection 37, which seals against water penetrating in the vertical direction.

FIG. 9 shows the wall section 32 with the adjoining wall section 38 and reveals the transverse toothing between the two wall sections and the position of the joint sealing tape 15, which is provided with a transverse flange 35 projecting on both sides.

The second embodiment of the formwork element shown in FIGS. 10 to 13 has a plate 41 which has on its front side two stiffening members 42 and 43 which extend in the longitudinal direction and are designed and arranged symmetrically to the longitudinal center plane. The stiffening members 42 and 43 are releasably connected to the plate 41 by screws 44 (Figs. 12 & 12), so that the plate 41 can, if necessary, be exchanged for another plate of different widths.

The stiffening members 42 and 43 each consist of a double T-beam 45 or 46, one flange of which rests on the plate 41 and the other flange of which forms a pressing surface 47 or 48 parallel to the plate. Inner surfaces 51, 52 are welded to the mutually adjacent inner ends of the flanges of the carriers 45 and 46, which form a receptacle 53 for the joint tape between them. The outer flanges of the supports 45 and 46 are partially shortened with an alternating inclination with respect to the longitudinal direction and with an inclination in the cross-sectional profile and are connected to one another at their outer ends by welded-in outer surfaces 55 and 56. These outer surfaces accordingly run with an inclination both in the transverse direction and in the longitudinal direction, which leads to a toothing of the adjoining concrete wall sections both in the horizontal and in the vertical direction. The stiffening members 42 and 43 are also provided at their ends with longitudinally inclined end faces 58 and 59, so _that they form closed hollow profiles. Furthermore, pairs of openings 60 and 61 are provided on the outside of the stiffening members 42 and 43 in the area of their strongest constriction, which taper conically from the front to the rear of the plate 41.

The plates 21 and 41 are provided, in a manner not shown but known, with connecting means in order to connect two or more formwork elements to one another on the end face and thereby to obtain a length corresponding to the diaphragm wall height.

Claims (10)

1. A method for producing diaphragm walls, in which wall sections adjoining one another on the end face are concreted in succession and sealed by a vertically running joint tape, preferably provided with a horizontal shoulder in the area of the baseplate connection, for which purpose a slot section is excavated in the length of the wall section to be produced Formwork element extending over the diaphragm wall, partially receiving the joint tape, which on its front facing the slot section has projections for interlocking the individual wall sections, is arranged vertically at the end of the slot section, the slot section is provided with a reinforcement cage, concrete using the contractor method in the slot section is inserted, the subsequent slot section is excavated on the back of the formwork element and vertically formwork element after release of the partially concreted joint tape ikal is excavated, characterized in that the concrete introduced into the slot section for filling cavities is also passed to the back of the formwork element, that when or after the excavation of the subsequent slot section on the back of the formwork element adhering concrete is chiseled off and that the formwork element is in front its vertical lifting from the manufactured wall section into the subsequent slot section is laterally pushed off. 2. The method according to claim 1, characterized in that the concrete is passed through the formwork element on its back. _3rd Formwork element for carrying out the method according to claim 1, consisting of an elongate plate (21, 41) with a flat rear side and with two stiffening members (22, 28;) provided on the front side of the plate and running essentially over the entire length of the plate (21, 41). 42, 43) have the outer surfaces (26, 29; 55, 56) which are inclined towards one another in the transverse direction and form between them a receptacle (23; 53) for the part (36) of the joint tape (15) to be embedded in the subsequent wall section (38) , characterized in that the stiffening members (22, 28; 42, 43) also have outer surfaces (24, 30; 55, 56, 58, 59) which are inclined in the longitudinal direction. 4. Formwork element according to claim 3, characterized in that the stiffening members (22,28; 42,43) are arranged at a distance from the longitudinal edges of the plate (21; 41). 5. Formwork element according to claim 3 or 4, characterized in that each stiffening member (22,28; 42,43) is designed as a welded hollow profile with at least one longitudinally extending stiffening rail (22; 45,46). Formwork element according to claim 5, characterized in that the longitudinally and transversely inclined outer surfaces (24, 26, 29, 30; 55, 56, 58, 59) are formed by sheet metal pieces welded to the stiffening rails (22; 45, 46) are. 7. Formwork element according to one of claims 3 to 6, characterized in that the stiffening members (22,28; 42,43) to the plate (21; 41) perpendicular, spaced inner surfaces (25; 51,52) which limit the receptacle (23, 53) for the joint tape (15). 8. Formwork element according to one of claims 3 to 7, _d a-characterized in that the stiffening members (4 ₂ , 43) have at their front end facing away from the plate (41) to the plate (41) parallel pressing surfaces (47, 48). 9. Formwork element according to one of claims 3 to 8, characterized in that the plate (21; 41) outside the stiffening members (22,28; 42,43) distributed over their length edge incisions and / or openings (27; 60,61) for the passage of the concrete to the back of the slab. 10. Formwork element according to one of claims 3 to 9, characterized in that the plate (41) releasably connected to the stiffening members (42,43) and thereby is interchangeable with a plate of width adapted to the diaphragm wall thickness.

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