DE9422291U1 - System for stabilizing the subsoil and for transferring building and traffic loads - Google Patents

Description

System for stabilizing the subsoil and for transferring structural and traffic loads

The present invention relates to a system for stabilizing existing fillings, dams, etc. and their often insufficiently load-bearing subsoil, as well as for transferring structural and traffic loads or service loads into the deeper, stable subsoil according to claim 1.

Areas dedicated to building or traffic must be designed in such a way that they can withstand the static and dynamic loads caused by the dead loads and traffic loads or the service loads of the building without causing damage, i.e. that these loads can be withstood without

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significant settlements, settlement differences and/or vibrations can be recorded.

In new buildings, this often requires stabilization of the insufficiently load-bearing subsoil as well as the load radiation areas and transfer of the loads to deeper, stable areas of the subsoil.

Existing fills, dams, etc., especially on subsoil that is not sufficiently stable, usually do not meet the above requirements. In these cases, it is necessary to stabilize the existing fills, dams, etc. and transfer the structural and service loads to the deeper, more stable subsoil.

According to the state of the art, various methods for improving the subsoil are known. In one group of methods, binding agent is introduced into a column-shaped area with or without replacing soil material, thereby solidifying this area. In another method, material such as gravel or similar is vibrated into the soil to be improved. These processes are repeated at spatial intervals so that a series of columns is created on which the road or structure is founded. One such method is disclosed, for example, in EP 0 170 503.

These methods require a large amount of binding agents or other materials for construction work, etc. However, these methods also have technical disadvantages for the traffic routes and structures that are to be built on them.

After approval for these methods, they are not suitable for subsoil with very soft ground.

In addition, constructive solutions are used, such as the installation of prefabricated piles or the production of piles or columns made of concrete or similar in insufficiently load-bearing subsoil with the help of drill pipes or similar.

Other methods involve the complete replacement of soil material, usually down to the solid subsoil. The soil that is not sufficiently stable is removed and replaced with sufficiently stable material, usually gravel sand or something similar.

According to DE 90 13 563.6, a series of tubular containers with a rectangular cross-section that are open at the top and bottom are used; the front container is driven into the ground, soil material is exchanged in the middle container, and the rear container is pulled out of the ground.

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DE 42 30 533 proposes another method for the continuous replacement of soil material, whereby a formwork arrangement consisting of two parallel, spaced vertical formwork walls is placed in the ground and the formwork walls are pushed forward horizontally in the working direction, after removing the soil in the front area between the formwork walls that does not have sufficient load-bearing capacity, whereby the rear area between the pushed-forward formwork walls is filled with new, particularly suitable soil material with intensive compaction. This method has particular advantages in terms of execution technology and economy, but large quantities of the soil that does not have sufficient load-bearing capacity must be excavated and removed and suitable soil must be transported and installed.

The object of the present invention is to create a system for stabilizing the subsoil of traffic routes and structures, in which a relatively small amount of soil material is exchanged and the structure and traffic loads are indirectly transferred to the load-bearing subsoil.

This object is solved by the features of claim 1. Advantageous embodiments are specified in the subclaims.

In the system for improving the subsoil and for transferring structural and traffic loads into the solid subsoil, according to the present invention, columns are produced at discrete locations, primarily in a grid-like manner, which consist of load-bearing material, such as gravel sand, rock or the like, and are coated with a tensile material, such as geotextile or the like, and are set down into the load-bearing subsoil.

The columns are constructed using temporary formwork, piping or similar in the subsoil. The soil that is not sufficiently stable is excavated from this formwork. This can be done by grabbing, drilling or spooling. The excavation takes place to a certain extent into the solid subsoil. Before the formwork is filled with stable material, such as gravel, sand, rock or similar, the formwork is lined with a tensile material that is introduced in the form of a ring or tube. By filling in the material, the casing is completely filled and stretched to a certain extent. As a result, the column fills the interior of the formwork almost completely. While the formwork or casing pipe is being pulled out, the filled, stable material is simultaneously compacted. Under the effect of this compaction and the weight of the filled material, an additional expansion is created.

of the column into the surrounding soil. This results in additional stretching of the casing.

In the surrounding soil, which does not have sufficient load-bearing capacity, a column of material with great rigidity is created, which is set into the load-bearing subsoil. The structural and traffic loads are transferred directly into the load-bearing subsoil. Due to their load-bearing capacity, the tensile-resistant columns are suitable for transferring loads into the load-bearing subsoil, even in soils with insufficient load-bearing capacity and a soft, even muddy consistency.

The columns with tensile strength casings can absorb vertical stresses in the installed material. The horizontal stresses are absorbed by the tensile strength of the casing. If the loads are increased during production, small vertical deformations occur, which result from the volume shift in the column as it becomes larger in circumference. As a result of the stretching of the casing, a greater tensile force builds up, which increases the load-bearing capacity of the column in a self-regulating manner.

When the columns are manufactured, the material is compacted in such a way that a sufficiently large horizontal tension is generated, which is maintained regardless of the existing load. The

The horizontal stress generated by the seal is always greater than that required to absorb the service loads. Therefore, there is no subsequent deformation or settlement under the service load.

During the manufacture of the column, the casing is only loaded and stretched to such an extent that, on the one hand, the required tension is achieved, but on the other hand, sufficient tensile force reserves are available, thus ensuring the permanent load-bearing effect.

By keeping the service loads, in particular the dynamic vibration effects, away from the poor, i.e. insufficiently load-bearing soil of the subsoil, which usually deteriorates as a result, an inherently stable, feedback-free support system is created.

The following can be considered for the flat material of the casing: reinforced or unreinforced geotextiles in single or multi-layer production, close-meshed wire mesh, prefabricated, impermeable or permeable pipes made of sheet steel, composite material made of metal and plastic, as well as a variety of combination materials made of geosynthetics and high-tensile tape and fiber material.

The load-bearing material of the filling is preferably a particularly hard, grain-graded material, such as gravel sand, rock, crushed grain, slag, waste material, recycled materials or the like, which may also be provided with a polymeric or hydraulically acting binding agent.

The compaction of the loaded load-bearing material can be achieved by shaking, vibrating or striking the formwork and/or the inner pipe as well as by tamping with a falling weight or ramming equipment or similar.

A further advantageous development of the idea is based on the possibility of integrating a drainage effect into the columns in order to enable pore water to drain from the subsoil that is not sufficiently load-bearing without fine particles of the soil migrating through the casing into the material of the columns. This can achieve long-term stabilization of the surrounding soil, which can then exert an additional supporting effect on the entire system.

The degree of stabilization of the subsoil can be determined by varying the column diameters, the spacing between the columns or the grid dimension and the choice of material.

The invention is explained below by way of example with reference to the accompanying drawings, in which:

Fig. 1 an area of the stabilized soil in a vertical section,

Fig. 2 a stabilized soil area in plan view and

Fig. 3 to 8 show the introduction of a stabilization column before setting the casing pipe (3), after excavating the insufficiently load-bearing soil material (4), after inserting the casing and filling it with load-bearing material (5), when pulling out the casing pipe (6), when pulling out the inner pipe and refilling the load-bearing material (7) and when completely pulling out the inner pipe (8) in a vertical section.

Fig. 1 shows a stabilized subsoil area with insufficiently load-bearing soil material 10 and a solid subsoil 12. In the soil area there are columns 14 made of load-bearing material, which have a casing in the form of a geotextile tube 16. The columns 14 are arranged in holes 18, which are in the non-

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sufficiently load-bearing soil material 10 and into the solid subsoil 12. The load-bearing material 14 is compacted so that the geotextile tube 16 is expanded into the adjacent soil area 10, 12 and is subjected to tensile stress. The columns 14 are approximately flush with the working subgrade 20 so that a load exerted from above is transferred by the columns 14 into the stable area 12 under tensile stress on the casing 16.

Fig. 2 shows a stabilized subsurface of a traffic route 22 between parallel side edges 24. The stabilization is achieved by means of three rows of evenly spaced cylindrical columns 26, each of which has load-bearing material 14 with a geotextile covering 16. The columns 26 are evenly distributed in a regular pattern across the width of the traffic route 22, so that overall a fraction of the total soil material under the traffic route surface is exchanged.

The creation of a column 26 is explained below using Fig. 3 to 8 as an example:

For this purpose, a jacket tube 30 and a slightly shorter and smaller diameter inner tube 3 2 are used.

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The inner tube 32 can, for example, be provided with a plurality of holes.

The method is carried out using an excavator as a carrier device for the vibration device, which is equipped with a leader 42. The leader 42 carries a gripping head 44 for gripping the pipes 30 and 32 and is equipped with a vibration vibrator 46.

Fig. 4 shows the end of a first work phase in which the excavator 40 has vibrated the casing pipe 30 into the soil material 10, which does not have sufficient load-bearing capacity, and into the solid subsoil 12 to a depth of about 1.5 m. Furthermore, the soil material contained in the casing pipe 30 has already been excavated, to a depth of 0.5 m into the solid subsoil. Depending on requirements, the casing pipe 30 is partially filled with water.

According to Fig. 5, in a second phase the excavator 40 has inserted the inner pipe 3 2 with a geotextile bag 16 pulled on it into the hole supported by the casing pipe 30. In addition, the inner pipe 3 2 is filled with gravel sand 14 or the like, whereby the sand can pass through the holes 34 into the intermediate space and fill the geotextile bag 16 and push it outwards.

Fig. 6 shows a third phase in which the excavator 40 pulls the casing pipe 30 while simultaneously vibrating. Due to the vibration effect, the gravel sand passes through the holes 34 of the inner pipe 32 into the surrounding annular space and stretches the geotextile 16. In the example, the geotextile is stretched by up to 5%.

In a fourth phase according to Fig. 7, the inner pipe 3 2 is pulled to a certain height at which gravel sand 14 is refilled.

Finally, Fig. 8 shows a fifth phase in which the excavator 40 completely pulls out the inner pipe 32 under vibration. The vibration effect of the perforated inner pipe 32 compacts the gravel sand 14 and the geotextile bag 16 expands into the surrounding soil areas 10, 12. Compaction can be controlled by changing the vibration frequency and the pulling speed.

After the inner tube 32 has been completely pulled out, the column 26 is completed in the ground.

Other possible processes for producing the columns include:

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a. Insert the geotextile bag/tube using a small diameter pipe. The backfill material is introduced through this pipe by slowly lifting the pipe while simultaneously adding more material from above. A vibrating or striking effect on the backfill pipe causes the material to flow continuously and compact it in the column to be created.

b. Inserting a prefabricated pipe with an external high-tensile banding into the cavity formed by the outer pipe. Pulling the outer pipe while the filled material below the base of the outer pipe is compacted so that the above-mentioned stress state is achieved in the interior.

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Claims (11)

1. System for stabilizing the subsoil and for transferring structural and traffic loads to stable areas, in particular the subsoil of traffic routes and structures or to the side thereof, with a plurality of columns inserted into the load-bearing subsoil at discrete locations, which are formed from a prefabricated tubular, hose or sack-shaped casing made of tensile but stretchable geotextile material and loaded with load-bearing grain-graded material, such as gravel sand, rock or the like, wherein the load-bearing material is compacted by expanding the casing. 2. System according to claim 1, characterized in that a prestress state is brought about in the column-shaped exchange region, which is not exceeded by the stresses of the use state. 3. System according to claim 1 or 2, characterized in that the tangential stresses caused by the expansion of the casing cause a permanent tension of the material in the column. 4. System according to claim 3, characterized in that the dynamic compaction achieves a prestress state in the soil body and the shell which is greater than the maximum stresses occurring under service load. 5. System according to one of claims 1 to 4, characterized in that the casing is made of flat material. 6. System according to claim 5, characterized in that a wire mesh is provided as the flat material. 7. Device for producing a system according to one of claims 1 to 6, characterized in that a casing pipe is provided as formwork. 8. Device according to claim 7, characterized in that an inner tube is provided for introducing the sheath into the jacket tube. 9. Device according to claim 7, characterized in that a longer core is provided for introducing the sheath into the jacket tube. 10. Device according to claim 9, characterized in that the core is designed as a support and filling tube. 11. Device according to claim 10, characterized in that the support and filling pipe has a plurality of holes.