EP0414120B1 - Method for making an impervious wall and machine for realizing such a method - Google Patents

Abstract

To make an impervious wall in a trench (1) in the ground stabilised by means of a supporting liquid (2), a formwork element (3) is arranged in the trench (1), which formwork element (3) subdivides the trench (1) in the transverse direction and is displaceable therein in the longitudinal direction, and the material (10) forming the impervious wall is fed into the trench (1) from above directly behind the formwork element (3) while the latter is being displaced and in such a way as to fill the space becoming free in the process. The formwork element (3) consists of a box-shaped housing (4) which has lateral wings (12) on its rear side which form a U-shaped (as viewed in horizontal section) space for the impervious-wall material (10) to be fed in. Vibrators arranged in supporting tubes (18) serve to consolidate the material. Cylinder-piston units (19) which are supported on the front wall (5) of the housing (4) can bring about the advance of the entire element (3). <IMAGE>

Description

The invention relates to two methods for producing a sealing wall according to the preambles of claims 1 and 2 and two devices for performing these methods.

The production of sealing walls in the ground is becoming increasingly important, particularly when coating landfills, particularly contaminated sites. A high diffusion resistance must above all be striven for in the sealing materials to be used.

Sealing walls in the form of diaphragm walls made of concrete or reinforced concrete are usually manufactured in sections according to the classic diaphragm wall construction. After lifting out a diaphragm wall section, a formwork element is inserted into the slit section, with the support of the floor being supported by a supporting liquid as formwork for the joint surface delimiting this section in the direction of production. This formwork element usually has the shape of a joint pipe, which creates a concave recess for the manufacture of the subsequent sections. The concrete is then poured in from the bottom up, displacing the support liquid upwards. The consumption of support fluid is relatively large.

Even if the subsequent sections are each concreted against the concave joint surface of the previous sections, the construction joints between the sections are risks for the tightness of the diaphragm wall, since the concrete of a subsequent section can only seal tightly against a carefully cleaned end face of the previous section. Since the concrete is placed under water while displacing the supporting liquid, it is impossible to avoid missing parts.

Similarly, in the generic method for producing a sealing wall from mineral sealing materials, in particular clay minerals, such as e.g. Montmorillonite, worked (DE 37 17 885 A1). In order to achieve a high diffusion resistance, the materials forming the sealing wall are premixed dry and, as a dry mixture, progressively introduced into the slit from bottom to top in sections extending over the entire height of the wall; the moisture required for the effectiveness of the mixture as a sealing layer is supplied after installation. To delimit the individual sections of the support wall, a formwork element dividing the slot in the transverse direction is again used.

Due to the dry installation of the sealing materials, a significantly denser storage with smaller pore spaces is possible compared to the installation of clay minerals in a moist, corresponding to the extraction or prepared by adding water; this applies in particular if what is possible with dry materials is mixed according to grain size. However, the construction joints between the individual sections still remain.

It has also become known to produce a sealing wall made of concrete or reinforced concrete directly at the creation of a slot in the floor in a continuous process (US Pat. No. 3,893,302). For this purpose, a device for simultaneously pulling and filling the slot is used, with which reinforcement cages are set immediately after the slot has been produced while avoiding intermediate support of the side walls, and concrete is introduced into the slot as the final filling material. For this purpose, the device which can be moved longitudinally along the slot comprises a slot over its entire depth dividing formwork element, which on the side facing the sealing wall to be formed has a formwork wall running transversely to the slot, on which vibrating devices for compacting the concrete to be introduced can also be arranged.

The invention has for its object to provide an economical possibility for the production of a tight and thus secure sealing wall from mineral sealing materials, in particular to avoid construction joints in the manufacture of such a sealing wall in the floor.

According to the invention, this object is achieved by the features contained in the characterizing parts of claims 1 and 2.

Devices for carrying out the method specify claims 3 and 4.

The invention is based on the knowledge that when a mineral sealing material, in particular a clay mineral is installed as a dry, free-flowing mixture in the dry state, when the formwork element is pushed forward, a kind of basic fracture is generated in the dry mass behind it, as a result of which the top layer is fed Sealing material slips. A specific basic fracture figure can be achieved by a specific shape of the wing walls, a possible inclination of the formwork wall or by exerting a vertical pressure on the freshly introduced material.

This enables continuous operation, with the result that the open slot length need only be short because slot excavation and sealing wall production can follow one another in synchronism. This is only very small amounts of support fluid required. Only volume losses have to be compensated; there is no need to prepare a suspension. This reduces the costs of preparing the support fluid and avoids environmental pollution from the disposal of a possibly contaminated support fluid.

When dry material is introduced into a comparatively narrow space of great height, the internal friction of the material plays a major role; it can have the consequence that, from a certain depth, the limit value of the vertical pressure becomes smaller than the fluid pressure in the supporting fluid. In order to prevent zones of lower density from being formed locally by any penetration of support liquid into the dry sealing material, the angle of the internal friction is reduced in the material forming the sealing wall, for example by application of vibrations, as a result of which a denser bearing and also a larger one are achieved Pressure against the support fluid can be caused. However, the active application of vertical and horizontal pressure by means of a rotating screw extending into the depth of the sealing wall material to be installed appears to be particularly advantageous. Alternatively, the sealing wall material can also be subjected to a vertical force according to claim 2.

The dry preparation and introduction of the sealant create the preconditions for the individual components of the mixture to be classified according to grain size and type of substance and to be put together according to appropriate recipes. In this way, not only a particularly dense storage of the sealants, but also a composition of the same can be achieved both according to the grain size and according to the type, which are matched to a particular extent to any pollutants that occur can.

With regard to the installation of the sealing layer, reference can be made to the content of DE 37 17 885 A1, and for the structure of the dry mixture from a coarse and a fine grain fraction to that of the older, but not previously published DE 38 23 874 A1. Their basic idea is to dimension the structure of the coarse grain fraction in a mixture of two inherently stable components, namely a fine and a coarse grain fraction, so that the fine grain can penetrate into the free pore spaces as if it were a liquid with low compression energy. This is the case if the largest grain of the fine grain fraction is equal to or less than approximately one tenth of the smallest grain of the coarse grain fraction. As long as it is dry, the total mixture is unstable with regard to the fine grain fraction. This allows filling of all pores of the grain structure up to close to the theoretical degree of sealing regardless of the delivery condition of the dry mixture. This instability of the dry mix is the prerequisite for achieving great homogeneity and density in the final state; The mixture obtains its stability when moisture is added and the cohesion of the fine particles is awakened.

In principle, a large number of mixture compositions are conceivable that meet these conditions, as long as only the requirement is met that the coarse grain structure, which can consist of one or more grain fractions, has a sufficiently large permeability for the fine grain and the volume of the fine grain fraction is equal or slightly larger is the pore volume of the coarse grain fraction. The confluence of the two material components can also be improved by using materials in the fine grain fraction which have a particularly small internal angle of friction, such as Montmorillonite. It has been shown that with such a mixture structure it is technically possible to achieve a pore volume of less than 15%. This allows a pore volume of 25 to 20% to be achieved, taking into account the scatter in the final sealing layer.

In order to prevent the dry clay minerals from absorbing moisture from the supporting liquid, for example in the area of the formwork element, during the installation of the sealing material in the dry state, thereby becoming sticky and adhering to the formwork element, it can be advantageous to make the dry constituents of the mixture hydrophobic, i.e. to be water-repellent. As a hydrophobizing agent e.g. Stearic acid can be used. Such hydrophobizing agents are expediently mixed in during the preparation of the dry mixture. The components of the dry mix have a very high internal friction, so that the added hydrophobizing agents are distributed evenly during mixing and form a thin film on the surface of the individual grains. Hydrophobing agents are generally organic compounds that degrade relatively quickly in the soil, so that the clay minerals can then absorb the moisture required for the sealing layer to function.

The devices according to claims 3 and 4 are specially adapted to introduce a dry mixture of a mineral sealing material so that the horizontal pressure of this material is equal to or greater than the hydraulic pressure of the supporting fluid, so that no flow around the formwork wall can occur through it , which could lead to defects in the sealing wall to be produced.

For this purpose, the formwork wall forms with side Wing walls an approximately U-shaped space for the sealing material to be introduced, which is a kind of funnel with a direct connection to the sealing wall to be produced. Due to the fact that the vibrating devices are not arranged on the formwork wall itself, but rather are arranged on or into the sealing wall extending pipes, it is possible to compress the dry material located within this space on the one hand and on the other hand when advancing the formwork element if there is one behind it Basic fracture figure forms to connect the newly installed material with the one already in place so that a faultless sealing wall is created.

If a screw extending into the depth of the slot is used to generate the horizontal pressure, then a vertical pressure is exerted on the material located in the U-shaped space, which causes a horizontal pressure in the depth which is equal to or greater than that hydraulic pressure of the support fluid to counteract this.

Fig. 1 und 2

Horizontal- und Vertikalschnitt durch eine erste Ausführungsform der Erfindung, die

Fig. 3 und 4

Horizontal- und Vertikalschnitt durch eine andere Ausführungsform der Vorrichtung nach der Erfindung und die

Fig. 5 und 6

Horizontal- und Vertikalschnitt durch eine weitere Ausführungsform der Erfindung mit einer vertikalen Schnecke zur Verdichtung des Dichtmaterials.

The invention is explained below with reference to the drawing. They show

1 and 2

Horizontal and vertical section through a first embodiment of the invention, the

3 and 4

Horizontal and vertical section through another embodiment of the device according to the invention and the

5 and 6

Horizontal and vertical section through a further embodiment of the invention with a vertical screw for compressing the sealing material.

A first embodiment of the invention is shown in FIG. 1 in a horizontal section and in FIG. 2 in a vertical section through a slot in which there is a device for introducing dry mineral sealing wall material.

As is shown above all in FIG. 2, in a slot 1 previously produced in any manner and filled in the usual way with a supporting liquid 2 there is a shuttering element 3 dividing the slot 1 in the transverse direction and extending over its entire depth. The shuttering element 3 consists of a box-shaped Housing 4 made of steel with a front wall 5 facing the supporting liquid 2, a rear wall 6 and side walls 7. The cavity formed by these walls is closed at the bottom by a base plate 8. The base plate 8 continues forward in a runner 9. The cavity enclosed by this box-shaped housing 4 is accessible from above. The rear wall 6 of the housing 4 also serves as a partition or formwork wall for the sealing wall material 10, which fills the slot 1 behind the direction of advance indicated by an arrow 11.

To introduce the sealing wall material 10, the box-shaped housing 4 is provided on its rear side with side wing walls 12 which, together with the rear or formwork wall 6, form a space 13 which is approximately U-shaped in cross section (FIG. 1). The wing walls 12 have a backward and outward slope; they can also slope from top to bottom to facilitate sagging of the sealant. At the lower end, the space 13 formed by the wing walls 12 and the rear wall 6 is closed by a drag plate 14 which extends the base plate 8. At the rear free edge of the drag plate, an apron 15 can be provided, which creates the seal to the sole 16 of the slot 1 in the event of unevenness. At the upper end of the U-shaped space 13 there is a storage container 17 for the sealing wall material 10 in the form of a filling funnel.

In this embodiment, the compression of the sealing wall material 10 is achieved by means of vibration devices (not shown) which are accommodated in support tubes 18. The support tubes 18 pass through the rear wall 6 and are supported against the front wall 5 of the housing 4 by cylinder-piston units 19. In this way, the advance can be achieved by extending the cylinder-piston units 19 while supporting the tubes 18 with respect to the sealing material 10 that has already been introduced and compressed of the entire formwork element 3 are effected. The tubes 18 can also be telescoped or provided with special support devices.

3 and 4, another embodiment of a formwork element 3 'is shown in representations similar to those described above. Here, too, the formwork element 3 'consists of a housing 4' with a front wall 5 ', a rear wall 6' and side walls 7 'and a base plate 8'. Lateral wing walls 12 ', a lower drag plate 14' and a storage container 17 'are also provided, as are tubes 18' with vibration devices (not shown) arranged therein.

In this formwork element 3 'the feed takes place by means of cylinder-piston units 20 which are arranged between the rear wall 6' and a special formwork wall 21 which can be displaced in the U-shaped space 13 'between the side wing walls 12'. This formwork wall 21 thus forms an abutment on the sealing wall for the cylinder-piston units 20, so that by means of the cylinder-piston units 20 the housing 4 'can be moved in the direction of arrow 11.

In the further embodiment shown in FIGS. 5 and 6, the form of the formwork element 3 ″ and the housing 4 ″ follows the embodiment of FIGS. 3 and 4, in particular also with regard to the feed with between the rear wall 6 ″ and a cylinder wall / piston unit 20 arranged in a formwork wall 22.

To compress the sealing wall material 10 there is a helical compression screw 23 with a vertical axis of rotation 24 in the U-shaped space 13 ″ formed by the wing walls 12 ″ and the formwork wall 22 arranged. The worm 23 is driven by a drive indicated at 25 with a conveying direction directed in the depth. The compression screw 23 can be designed as a screw conveyor. However, a design of the screw 23 in the manner of a baroque spiral column with a circular cross section appears to be particularly expedient. Such a screw not only causes material to be conveyed in the direction of its longitudinal axis, but is also capable of exerting pressure on the material in the horizontal direction, so that the material moving in from above through the hopper 17 '' also usually moves sideways to press unavoidable unevenness into the slot walls. In order to avoid discontinuities, in particular also incorrect loading of the screw 23, care must be taken to ensure that the horizontal feed of the screw 23 and the housing 4 ″ take place synchronously.

Claims (13)

1. A method of constructing a sealing wall from mineral sealing materials, in particular clay minerals, for example montmorillonite, in a channel (1) in the ground stabilised by a supporting fluid, in which the material forming the sealing wall is premixed in a dry state and is introduced as a dry free-flowing mixture, while displacing the supporting fluid, into a channel section partitioned in a transverse direction by a shuttering element (3, 3', 3''), and the moisture required to render the mixture effective as a sealing wall is supplied after its introduction, characterised in that the shuttering element (3, 3', 3'') is shifted in the channel (1) in the longitudinal direction thereof and the material (10) forming the sealing wall is introduced into the channel from above during the shifting of the shuttering element (3, 3', 3'') immediately behind the latter, thus filling up the space left free during the shifting, and in that during the introduction of the material (10), in order to create a horizontal pressure which is equal to or greater than the hydraulic pressure of the supporting fluid, said material is acted upon, for example, by vibrations applied by vibrators or the like with a view to reducing the angle of the internal friction.
2. A method of constructing a sealing wall from mineral sealing materials, in particular clay minerals, for example montmorillonite, in a channel (1) in the ground stabilised by a supporting fluid, in which the material forming the sealing wall is premixed in a dry state and is introduced as a dry free-flowing mixture, while displacing the supporting fluid, into a channel section partitioned in a transverse direction by a shuttering element, and the moisture required to render the mixture effective as a sealing wall is supplied after its introduction, characterised in that the shuttering element (3, 3', 3'') is shifted in the channel (1) in the longitudinal direction thereof and the material (10) forming the sealing wall is introduced into the channel from above during the shifting of the shuttering element (3, 3', 3'') immediately behind the latter, thus filling up the space left free during the shifting, and in that during the introduction of the material (10), in order to create a horizontal pressure which is equal to or greater than the hydraulic pressure of the supporting fluid, it is acted upon by a vertical force, for example, by an applied load or by means of a screw extending into the depth of the channel.
3. An apparatus for carrying out the method according to Claim 1, with a shuttering element (3, 3') which partitions the channel (1) into sections over its entire height and which is provided with means for longitudinal shifting in the channel (1), wherein on the side nearest the sealing wall to be formed the shuttering element (3, 3') has a shuttering wall (6, 6') which extends substantially transversely to the channel (1) and on which vibrating appliances are mounted, characterised in that the shuttering wall (6, 6') is provided with lateral wing walls (12, 12') which, viewed in horizontal section, form with the shuttering wall an approximately U-shaped cavity (13, 13') for the sealing material (10) to be introduced, and in that the vibrating appliances, e.g. vibrators, mounted on the shuttering element (3, 3') are disposed on or in tubes (18, 18') extending horizontally into the sealing wall.
4. An apparatus for carrying out the method according to Claim 2, with a shuttering element (3'') which partitions the channel (1) into sections over its entire height and which is provided with means for longitudinal shifting in the channel (1), wherein on the side nearest the sealing wall to be formed the shuttering element (3'') has a shuttering wall (6'') which extends substantially transversely to the channel (1), characterised in that the shuttering wall (6'') is provided with lateral wing walls (12'') which, viewed in horizontal section, form with the shuttering wall an approximately U-shaped cavity (13'') for the sealing material (10) to be introduced, and in that a driven screw (23) is arranged in the U-shaped cavity (13''), with a direction of rotation directed into the depth of the channel (1).
5. An apparatus according to Claim 3 or 4, characterised in that the U-shaped cavity (13, 13', 13'') formed by the wing walls (12, 12, 12'') is closed at the lower end by a trailing plate (14, 14', 14'').
6. An apparatus according to Claim 5, characterised in that a skirt (15) sealing against the floor (16) of the channel (1) is provided on the free edge of the trailing plate (14, 14', 14'').
7. An apparatus according to any one of Claims 3 to 6, characterised in that the inner surfaces of the wing walls (12, 12, 12'') are inwardly inclined.
8. An apparatus according to any one of Claims 3 to 7, characterised in that the shuttering wall (6, 6', 6'') is inclined in a vertical direction.
9. An apparatus according to any one of Claims 3 to 8, characterised in that a reservoir (17, 17', 17'') for the sealing wall material (10) is disposed above the U-shaped cavity (13, 13', 13'') formed by the shuttering wall and the wing walls.
10. An apparatus according to any one of Claims 3 to 9, characterised in that cylinder-piston units (20) bearing against the sealing wall are provided for advancing the shuttering element (3, 3', 3'').
11. An apparatus according to Claim 10, characterised in that the cylinder-piston units (20) are connected so as to be locked in movement with the tubes (18, 18') which can bear against the sealing wall .
12. An apparatus according to Claim 11, characterised in that the tubes (18, 18') comprise sections which can be displaced telescopically relative to one another.
13. An apparatus according to Claim 12, characterised in that the shuttering wall (6',6'') is in the form of a double wall and the cylinder-piston units (20) are disposed between the wall portions (6, 6'' and 21, 22) with a movement direction extending in the longitudinal direction of the wall.

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