EP0414120A1 - 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 a method for producing a sealing wall from mineral sealing materials, in particular clay minerals, in a slot in the floor stabilized by means of a supporting liquid, and to a device for carrying out this method.

The production of sealing walls in the ground is becoming increasingly important, particularly when encasing landfills, particularly contaminated sites.

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 a method of the type specified at the outset 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.

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 procedurally in that the formwork element is displaced in the slot in its longitudinal direction and that the sealing wall forming dry material in the course of shifting the formwork element immediately behind it from above and filling the space that is freed during the shifting is installed under a horizontal pressure in the slot that is equal to or greater than the hydraulic pressure of the supporting fluid.

During the introduction of the material forming the sealing wall, this can be done in the sense of reducing the angle of the internal friction, e.g. with vibrations from vibrators or the like.

It is also possible for the material forming the sealing wall to be applied with vertical pressure, e.g. by load and / or horizontal pressure e.g. by a screw reaching into the depth of the slot.

The basic idea of the invention is to design a formwork element which divides the diaphragm wall in the transverse direction so as to be displaceable in the longitudinal direction of the diaphragm wall and to introduce the material forming the sealing wall in the course of advancing this formwork element. A cavity created directly behind this by pushing the formwork element is filled from above by refilling sealing 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. As a result, only very small amounts of support fluid are 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.

Since the sealing material is installed in a dry state as a dry, free-flowing mixture of mineral sealing materials, in particular clay minerals, when the formwork element is pushed forward, a kind of fracture is created in the dry mass behind it, as a result of which the sealing material supplied from above 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 and / or horizontal pressure on the freshly introduced material.

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, provision is made for the material forming the sealing wall to be installed with a horizontal pressure which is equal to or greater than the hydraulic pressure of the support liquid. If gravity, in particular the effect of a load, is not sufficient for this, it can be passive, e.g. by applying vibrations, the internal friction of the material is reduced, a denser bearing is achieved and a greater pressure against the supporting fluid is also brought about. 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.

The dry preparation and introduction of the sealant create the prerequisite for ensuring that the individual components of the mixture according to grain size and type of substance classified and can 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 that can be matched to a particular extent to any pollutants that may occur.

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 becomes stable when moisture is added and the cohesion of the fine particles is awakened.

In principle, a large number of mixture compositions are conceivable which satisfy 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 has the fine grain and the volume of the fine grain fraction is equal to or slightly larger than 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 invention further relates to a device for carrying out the method with a formwork element which divides the slot over its entire height and is provided with means for longitudinal displacement in the slot, that on the side facing the sealing wall to be formed has an essentially transverse to the slot shuttering wall with side wing walls, which, seen in horizontal section, form an approximately U-shaped space for the sealing material to be introduced with the shuttering wall.

In accordance with the two different procedures described for applying a horizontal pressure to the material to be installed, vibrating devices, e.g. Vibrator, arranged or a driven screw with a vertical axis of rotation and in the depth of the slot conveying direction can be arranged on the formwork element in the U-shaped space formed by the wing walls.

The U-shaped space formed by the wing walls can be closed off at the lower end by a drag plate. An apron sealing against the sole of the slot can be provided on the free edge of the drag plate.

The inner surfaces of the wing walls can be inclined inwards and the formwork wall in the vertical direction.

A storage container for the sealing wall material can be arranged above the U-shaped space formed by the formwork wall and the wing walls.

The vibration devices are expediently arranged on or in tubes extending into the sealing wall.

To advance the formwork element, cylinder-piston units supporting against the sealing wall can be provided, which are expediently connected to the pipes that can be supported against the sealing wall in a non-positive manner. The Pipes expediently consist of telescopically displaceable sections.

Finally, the formwork wall can be designed as a double wall and the cylinder-piston units can be arranged between the wall parts with a direction of movement extending in the longitudinal direction of the wall.

• 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
• 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 height. The shuttering element 3 consists of a box-shaped Housing 4 made of steel with a front wall 5 facing the supporting liquid 2, one 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 telescopic or provided with special support devices.

3 and 4 is shown in a similar representation as described above, another embodiment of a formwork element 3 '. 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.

The feed takes place in this formwork element 3 'by cylinder-piston units 20 which are arranged between the rear wall 6' and a special formwork wall 21 which is' 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.

5 and 6, the configuration 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 formwork wall 22 arranged cylinder-piston units 20th

To compress the sealing wall material 10, a helical compression screw 23 with a vertical axis of rotation 24 is here 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 able to exert pressure on the material in a horizontal direction, so that the material moving up through the hopper 17˝ from above does not usually move to the side unevenness to be pressed into the slot walls. In order to avoid discontinuities, in particular also incorrect loading of the screw 23, it must be ensured, however, that the horizontal feed of the screw 23 and the housing 4˝ take place synchronously.

Claims (15)

1. Method for producing a sealing wall from mineral sealing materials, in particular clay minerals, such as Montmorillonite, in a slot in the floor stabilized by a supporting liquid, in which the material forming the sealing wall is premixed dry and installed as a dry, free-flowing mixture, displacing the supporting liquid in a slot section divided by a formwork element in the transverse direction and which is necessary for the effectiveness of the mixture as a sealing wall Moisture is supplied after installation, characterized in that the formwork element (3, 3 ′, 3˝) is displaced in the slot (1) in its longitudinal direction and the dry material (10) forming the sealing wall in the course of the displacement of the formwork element (3 , 3 ', 3˝) immediately behind this from above and the space that becomes free when moving is installed under a horizontal pressure in the slot that is equal to or greater than the hydraulic pressure of the supporting fluid. 2. The method according to claim 1, characterized in that during the introduction of the material forming the sealing wall (10) on this in the sense of a reduction in the angle of the internal friction e.g. is vibrated by vibrators or the like. 3. The method according to claim 1, characterized in that the material forming the sealing wall (10) during the introduction with vertical pressure e.g. by load and / or horizontal pressure e.g. is acted upon by a screw extending into the depth of the slot. 4. Device for performing the method according to claim 2 with a the slot over its entire height dividing and provided with means for longitudinal displacement in the slot shuttering element, which on the side facing the sealing wall to be formed has a shuttering wall which runs essentially transversely to the slot and has side wing walls which, seen in horizontal section, has an approximately U-shaped space for the sealing material to be introduced with the shuttering wall form, characterized in that on the formwork element (4, 4 ') in the horizontal direction extending into the sealing wall vibrating devices, such as vibrators, are arranged. 5. Apparatus for carrying out the method according to claim 3 with a slot dividing the slot over its entire height and provided with means for longitudinal displacement in the slot shuttering element, which on the side facing the sealing wall to be formed has an essentially transverse shuttering wall with side wing walls , seen in horizontal section with the formwork wall form an approximately U-shaped space for the sealing material to be introduced, characterized in that on the formwork element (4˝) in the U-shaped space (13˝) formed by the wing walls (12˝) driven screw (23) with a vertical axis of rotation (24) and in the depth of the slot directed conveying direction. 6. Apparatus according to claim 4 or 5, characterized in that the U-shaped space (13, 13 ', 13˝) formed by the wing walls (12, 12', 12˝) at the lower end by a drag plate (14, 14th ', 14˝) is complete. 7. The device according to claim 6, characterized in that on the free edge of the drag plate (14, 14 ', 14˝) against the sole (16) of the slot (1) sealing apron (15) is provided. 8. Device according to one of claims 4 to 7, characterized in that the inner surfaces of the wing walls (12, 12 ', 12˝) are inclined inwards. 9. Device according to one of claims 4 to 8, characterized in that the formwork wall (6, 6 ', 6˝) is inclined in the vertical direction. 10. Device according to one of claims 4 to 9, characterized in that above the U-shaped space (13, 13 ', 13˝) formed by the formwork wall and the wing walls, a storage container (17, 17', 17˝) for that Diaphragm wall material (10) is arranged. 11. The device according to claim 3, characterized in that the vibration devices are arranged on or in the sealing wall extending tubes (18, 18 '). 12. Device according to one of claims 4 to 11, characterized in that for advancing the formwork element (3, 3 ', 3˝) against the sealing wall supporting cylinder-piston units (20) are provided. 13. The apparatus according to claim 12, characterized in that the cylinder-piston units (20) with the support against the sealing wall tubes (18, 18 ') are connected in a non-positive manner. 14. The apparatus according to claim 13, characterized in that the tubes (18, 18 ') consist of telescopically displaceable sections. 15. The apparatus according to claim 14, characterized in that the formwork wall (6 ', 6˝) formed as a double wall and the cylinder-piston units (20) with in Wall longitudinal direction of movement between the wall parts (6 ', 6˝ and 21, 22) are arranged.

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