WO1999011870A1 - Method and sheathing for producing a ground column to support building or travelling loads - Google Patents

Abstract

The invention relates to a method for producing ground columns (28, 86, 88) to support building or travelling loads, wherein a tubular encasing (10) is driven into the ground in a stationary zone, the ground material is removed from the tubular encasing (10), a sheathing (16) made of geotextile material is inserted into the tubular encasing (10) and filled with a load-bearing, granulated, loose material (24), the load-bearing material (24) is subsequently compacted and the tubular encasing (10) is removed. An individual jacket tube for each ground column (28, 86, 88) is driven into the ground, the jacket tube (10) is emptied by excavation, a sack-like sheathing (16) with a diameter that is larger than the diameter of the inner diameter of the tubular jacket (10) is introduced into the empty jacket tube (10) and the granulated material (24) progressively presses the sheathing (16) against the stationary supporting layer and the inner wall of the tubular jacket (10) during filling. The granulated material (24) is so compacted upon removal of the jacket tube (10) that the sheathing (16) extends beyond its original diameter until the opposing forces produced by the compacted ground around it are approximately balanced out. The material of the sheathing (16) is endowed with sufficient penetrability qualities so that no surrounding earth can penetrate into the column (28, 86, 88) thus formed.

Description

 Process and casing for the production of a soil column for the removal of building or traffic loads

The invention relates to a method for producing a floor pillar for the transfer of building and traffic loads according to the preamble of claim 1.

From DE 195 18 830 a method for stabilizing the subsoil and for removing structural and traffic loads has become known, in which a columnar area of insufficiently stable soil material is excavated at discrete points, into the excavated hole a sheathing made of elastic, relatively tensile, filter-like material is introduced. The sheathing is filled with granular material, which is then compacted by widening the sheathing in such a way that the surrounding soil absorbs the horizontal tension through part solidification. The covering consists of flat material, in particular reinforced or unreinforced geotextiles. The granular material is a hard grain-graded material, such as gravel sand, stone, crushed grain, slag, mining material, recycling materials or the like, to which polymeric or hydraulically acting binders may have been added. The filled material is compacted by shaking, vibrating or hitting the formwork, if necessary also with the aid of ramming devices or the like.

This creates a material column with great rigidity in the non-load-bearing soil, which is set down in the load-bearing subsoil. The building and Traffic loads are transmitted on the one hand to the load-bearing soil and, on the other hand, absorbed by the load radiation in the surrounding soil. The surrounding soil is compacted and partially consolidated in the process described and is therefore able to absorb horizontal forces.

For the manufacture of a column, the known method is such that a jacket tube is driven into the ground and then emptied inside. The covering is then inserted into the jacket tube on an inner tube with a smaller diameter. The granular material is fed into the inner tube, after which the jacket tube is then shaken out under compression and then also the inner tube. Such a method leads to satisfactory results, but is relatively complex.

It is therefore an object of the invention to provide a method for producing a floor pillar for the removal of building and traffic loads, which can be operated with less effort and leads to particularly favorable results.

This object is solved by the features of claims 1 and 2.

In the invention it was recognized that a single tube is sufficient for the creation of a floor column. In the solution according to claim 1, a single jacket tube is driven into the ground and emptied as usual by reaching out. A sack-like covering made of flexible material is then inserted into the empty jacket tube. The sack-like covering therefore hangs more or less deep into the casing tube and has an irregular moderate, in this case not yet expanded shape. By filling in the granular material, however, the sack-like covering can be advanced to the bottom of the casing tube, which is formed by the load-bearing layer. Further filling of the granular material leads to the sack-like covering gradually being completely in contact with the sole and the wall of the casing tube. If necessary, a certain tension must be constantly provided at the upper end of the sack-like covering, which protrudes from the upper end of the casing tube, so that unnecessary wrinkles do not occur. Despite the tension, however, a compliance must be ensured so that a full contact of the covering on the sole and on the wall of the casing tube is guaranteed. It is essential to the invention, however, that the casing has a larger diameter than the inside diameter of the casing tube. When the casing pipe is pulled out of the ground and the granular material in the casing is simultaneously compacted, the column is also expanded horizontally or radially, which already has a larger diameter than the inner diameter of the casing pipe if the material of the bag-like casing has not yet been expanded. The intensive compression of the filler material also leads to an expansion of the geotextile material, which results in an additional horizontal expansion of the column. The process described leads to a corresponding compaction of the surrounding, otherwise unsustainable material, until a balance is established between the horizontal forces exerted during compaction and the counter-forces generated in the surrounding soil, part of the stresses being generated by the compaction Material of the wrapping is collected. In this way, a pillar is created that guarantees an effective transfer of building and traffic loads even with very soft, unsustainable floors. In the method according to claim 2, a single tube is also used, but which is designed as a displacement tube. It is therefore provided with a closure during driving so that soil does not penetrate into the interior of the displacement pipe. It is understood that when using a jacket tube according to claim 1, its diameter can be larger than that of the displacement tube. Economically, displacement pipes can only be shaken into the ground up to a certain diameter.

Displacement pipes, the lower end of z. B. is closed by a flap, are known per se, for example from DE 296 11 427. Instead of a smooth displacement tube which can be closed at the bottom by a corresponding closure, a tube can also be used according to the so-called displacement drilling method. In this tube, a helix or the like is arranged on the outside, so that a feed into the ground is obtained by appropriate rotation. This method does not require the use of a vibrator. The tube is also pulled out after the casing has been filled by rotation.

In the method according to the invention according to claim 2, the sack-like covering is inserted into the displacement tube, the diameter of the sack-like covering approximately corresponding to the inside diameter of the displacement tube or also being larger than the inside diameter. The complete insertion of the casing or the lining of the displacement tube with the casing is carried out in the same manner as has already been described for claim 1. After the granular material has been poured in and the displacement pipe has been lined appropriately with the covering, it is then compacted and, if necessary, simultaneously ges shaking out the displacement tube, with the lower end now open. If two flaps forming a roof are used, this happens automatically. However, it can also be considered to provide a so-called lost tip that remains in the ground when the displacement tube is pulled.

The surrounding material is already partially compacted by driving in the displacement pipe. By compacting the granular material in the casing, especially when pulling the displacement tube, a further compacting step takes place to the extent that a balance is again established between the horizontal tension of the column towards the outside and the reaction forces in the surrounding soil. Here, too, an effective transfer of loads is obtained.

In both cases, the columns formed in this way are such that the column remains intact even when the column sections are deflected horizontally or the columns are spread apart.

Soil columns produced by the method according to the invention are also used on substrates with a high groundwater level. There is then a risk that the groundwater will penetrate the column under strong pressure and push the material up or flush it. In order to produce an intact soil column even under such conditions, one embodiment of the invention provides that a mixture of sand and bentonite is filled into the lower region of the casing over a certain height, for example with a volume fraction of 6 to 15% bentonite. Bentonite is known to have waterproof properties. When water enters the column, there is therefore a watertight plug in the lower area of the floor column, which prevents further water penetration.

It has already been mentioned that a displacement pipe using the drilling displacement method can also be used. As the displacement tube is unscrewed, there is a relative rotation between the tube and the filled casing. In order to protect it and not to weaken it, an embodiment of the invention provides that a protective cover is arranged between the displacement tube and the casing, which, for. B. can consist of a fleece. The fleece only has the task of protecting the casing from mechanical damage while unscrewing the displacement tube. Then it has no function.

Often, the poorly loadable floor, which is to be stabilized with the help of the floor columns, is below a load-bearing layer that either already exists or has been applied later. In the manufacture of the soil column, it is necessary to drive the pipe through this layer into the unsustainable soil into a lower, stable layer. On the other hand, it would be sufficient to have the soil column only extend over the soil layer that is unsustainable. However, if the casing is led to the upper end of the formwork tube, more geotextile material is required than is required for the floor column. Therefore, an embodiment of the invention provides that the sheath is pushed onto an inner tube and frictionally attached to the inner tube at a distance from the upper end such that the sheath slips on the outside when filling with the granular material and when the inner tube is pulled up. With this method it can be ensured that the covering has only a length which is really necessary for the soil column. It will therefore be a considerable amount of geotextile material saved, which is produced due to the required tensile strength with relatively high material and manufacturing costs. An inner tube has the further advantage that it can be provided with a funnel, through which the granular material can be filled more easily into the casing.

The driving of the tube in the method according to the invention preferably takes place with the aid of a vibrator which can be varied in amplitude and frequency and which also has the ability to optimize the driving in process. During the driving-in process, the propulsion per unit of time is determined and the amplitude and frequency at which an optimal result is achieved. Since the manufacture of floor columns u. a. depends on how quickly the pipes can be driven into the ground, it is also advantageous to apply a preload to the vibrator, which can be up to 20 to 25 t. It has been found that the drive-in process can be drastically reduced in time with the aid of such a preload.

The diameter of the floor columns naturally depends on the diameter of the pipes in question. When driving in open pipes at the lower end, a diameter of 1.2 to 1.5 m is possible. In the case of a displacement pipe, the upper limit is 1 m in diameter. Pipes with a diameter of 80 cm are preferably used for this. The diameter for the columns covered with geotextile is made from sand or similar rolled material. The strength of the improved floor can then also be determined from this, which results from the arrangement of the floor columns according to a predetermined grid. According to a further embodiment of the invention, it is advantageous if after the introduction of floor columns with a geotextile jacket, further floor columns are subsequently introduced according to the described method, which are each arranged between the floor columns already introduced. They consist only of sand and therefore have no covering made of geotextile material. The introduction is carried out in the same way as described above, using an open-ended or a displacement pipe, which is then filled with a suitable granular material, preferably sand, and in which the pipe is pulled out with simultaneous compression to form a compacted soil column made of sand. Sand has the advantage that its volume is hardly changed when it is compacted.

The method described is advantageous in that a certain soil strength is achieved with a minimum of soil columns with geotextile sheathing. The manufacturing and material costs are therefore drastically reduced.

When creating structures or traffic routes, such as. B. at a dam, it can happen that, for. B. with a widening also a noticeable horizontal force component occurs. The floor columns according to the invention can absorb horizontal loads, but only to a certain extent. Therefore, an embodiment of the invention provides that the floor columns are introduced at an angle to the vertical in the area of a significant horizontal component. Such inclined floor columns are therefore more suitable to counteract shear loads. It is understood that the inclination takes place in a direction that counteracts the horizontal component that occurs. According to one embodiment of the invention, the covering consists of a suitable geotextile material, namely a woven fabric or a grid, optionally in combination with a nonwoven fabric. It must be provided with a sufficiently high strength, which is between 20 to 500 kN / m for such coverings that have a seam. As is known, a seam is a weak point, so that the seam reduction factor is decisive for the design of the nominal strength. If, on the other hand, the covering is produced using the round process, a material with approximately half the required nominal strength can be used for a covering with a seam. A strength of at least 150 kN / m should preferably be provided for coverings with seams and about half of this for coverings produced using the round process.

Such wrappings are preferably produced in a round process, i. H. seamlessly made. Otherwise, it is easiest if the covering is formed from a wide web of the desired material, which is placed on top of one another and connected by a special seam at the open edge. The connection is made by weaving the ends or with appropriate suture material.

The load on the geotextile material cover varies in height. It may therefore be advantageous to adjust the strength of the load. According to the invention, one possibility is that the warp threads of the fabric run in the longitudinal direction of the covering and the weft threads run transversely thereto and zones of different strength are obtained by varying the spacing of the weft threads. If the weft threads are close together, the strength is known to be higher than if they are further apart. Another way is through the hose-like sheath to pull a sheath of limited length also from geotextile material, which then increases the strength in this area.

An embodiment of the method according to the invention is explained in more detail with reference to drawings.

1 to 4 show schematically different phases in the manufacture of a soil column using the method according to the invention.

Fig. 5 shows part of the fabric of an envelope for a soil column produced by the method according to the invention.

Fig. 6 shows schematically the introduction of a casing into a pipe located in the ground with the help of an inner pipe.

7 schematically shows a displacement pipe according to the drilling displacement method.

Fig. 8 shows schematically the shaking in of a pipe after the displacement process.

Fig. 9 shows schematically the arrangement of floor columns according to the invention.

Fig. 10 shows schematically the introduction of floor columns in a dam widening. In Fig. 1 it can be seen how a casing tube 10, which for example has a diameter of 1 m, is driven into a bottom layer 12 which consists of non-load-bearing material. The casing tube 10 is driven into a load-bearing layer 14 below the layer 12, for example 1.5 m. The jacket tube 10, however, extends to a certain extent above the layer 12. The jacket tube 10 is driven in in a known manner by appropriate vibrators. This will be discussed in more detail below.

W ^τ ie further in Fig. 1 can be seen, hangs a bag-like cover 16 in the pipe 10, which has been previously emptied by reaching out to the level 20, which is formed by the load-bearing layer 14. When the bag-like sheath 16 is fully stretched, its diameter is larger than the inside diameter of the casing tube 10, for example up to 10%. By simply lowering the casing 16, it hangs more or less unregulated inside the casing tube 10, the upper end 22 being placed around the edge of the casing tube 10 and held in place by suitable means, e.g. B. by a strap. Then granular material, such as. B. sand, as described in DE 195 18 830, filled. The filling of the first quantities leads to the casing 16 being placed under vertical tension so that it can sag to the level 20 by giving in at the edge. Further filling with granular material leads to the fact that the sheath 16 is gradually pressed against the bottom 20 and the wall of the casing tube 10, wherein by holding the upper edge 22 of the sheath 16 it is ensured that this is under more or less tension . The complete filling of the casing tube with simultaneous application of the sheath 16 is shown in Fig. 2. The level of the filled material 24 is slightly below that upper edge of the casing tube 10, in any case above the level of the layer 12.

3 shows how the casing tube 10 is pulled out in the direction of arrow 26. This takes place with compression of the filled material 24. The compression can be carried out either solely by the vibration of the pulled-out casing tube 10 and / or by using conventional compression techniques. Since the casing 16 has a larger diameter than the inner diameter of the casing tube 10, there is a corresponding widening of the column formed in this way, an additional widening occurring horizontally or radially in that the material of the casing 16 yields in accordance with its stress-strain characteristic . After the casing tube 10 has been completely pulled out and correspondingly compressed, a base column 28 results, as shown in FIG. 4, the upper end of which corresponds to the level of the layer 12. It is used to transfer building and traffic loads together with other floor columns, not shown, which are created according to a certain grid. It is understood that a stabilizing base layer of z. B. 1 to 1.5 m thickness can be applied, which is not shown here.

In Fig. 3 it can be seen that due to the compression of the material 24, a force is exerted on the surrounding material 12, indicated by arrow 30. The surrounding material 12 is in turn compressed and builds up a reaction force 32. After the final creation of the column 28, the forces 30, 32 are in equilibrium, and a part of the forces 30 can be absorbed by the tension of the covering 16. A similar procedure is used to create a floor column using the displacement method, but the tube is driven in using the displacement method, so that it is no longer necessary to empty the tube. In the displacement process, however, the tube has a slightly smaller outside diameter than in the process described above, for example only up to 0.8 m.

In the lower region of the material 24 it is indicated in FIGS. 2 to 4 that a type of stopper is formed with the aid of a mixture of granular material, e.g. B. sand and bentonite, the latter being added in a proportion of 6 to 15%. It has the property that swelling and compression occur when water penetrates, so that further penetration of water, for example groundwater, into the material of the column is avoided.

The covering for the column is preferably produced using the round method, so that seams, which are naturally weak points, are avoided. A suitable plastic material is used, which is able to absorb considerable loads up to 500 kN / m. Preferably, a lattice or fabric-like structure is used, which is designed so that on the one hand the entry of water is possible, but not the passage of material from the surrounding soil. The filter effect can be improved by using built-in fleece material. 5 shows a section 36 of such an envelope. The warp threads 38 run in the vertical direction, while the weft threads 40 run in the horizontal direction. As can be seen in FIG. 5, the spacing of the weft threads 40 in the vertical direction is different. This enables a zone of increased strength to be created in the casing. The material of the covering is chosen so that it can absorb a considerable tensile stress, but allows a certain amount of stretch to compact the surrounding soil in order to build up a reaction force to equilibrium. This process takes place relatively quickly. Later settlements hardly ever occur.

1 and 2, the sheath extends beyond the top of the tube. In many cases, however, there is already a base layer of sufficient or suitable quality above the soil layer to be stabilized. The formwork tube must therefore first be brought through this layer and then through the layer to be stabilized down to the load-bearing layer. On the other hand, however, the floor pillar only needs to extend over the height of the layer to be stabilized. The method described with reference to FIGS. 1 and 2 therefore requires a larger amount of geotextile material than is ultimately required for the soil column. FIG. 6 now shows how the pipe 10 according to FIGS. 1 and 2 has been driven through a support layer 42 placed on the layer 12 to be stabilized. The lower end of the tube 10 is not shown. As can also be seen, an inner tube 44 is provided, over which the sheath 16 is drawn, so that the sheath 16 with the inner tube 44 can be introduced into the tube 10. The special thing is that the upper end of the casing 16 is attached at a distance from the upper end of the inner tube 44 on its outer wall, for example with a tensioning strap 46 or the like. In the finally introduced state, the sheath 16 therefore only extends to the top of the layer 12 to be stabilized. The inner tube 44 has a funnel 48 at the upper end. through which granular material can be filled. With the Filling the inner tube 44 is pulled out, but the envelope 16 remains in place. The attachment 46 is only frictional and slides on the inner tube 44 when it is pulled out. After the casing 16 has been completely filled, as is illustrated with reference to FIGS. 2 to 4, the tube 10 can then be removed in the manner already described with the aid of a vibrator or the like.

In Fig. 7 a Bohrverdrängungsrohr 50 is indicated, which has a helical coil 52 on its outside for screwing into the ground. The tube 50 can in turn have a suitable closure at the lower end, which is closed when screwed into the ground, but opens when unscrewed. As can also be seen in FIG. 7, an envelope 54 is inserted, similar to that described with reference to FIG. 1. The casing can have an inner diameter which corresponds to the inner diameter of the tube 50 or can also be somewhat larger. Between the sheathing 54, which can be similar in structure to the sheathing 16, a nonwoven layer 56 is arranged between the sheathing 54 and the tube wall. The non-woven layer serves to protect the casing 54 filled with granular material when the pipe 50 is unscrewed from the ground.

8, a vibrator 60 is indicated schematically, which holds a bear 64 via a rope 62, to which a displacement tube 66 is attached. Furthermore, it can be seen that a deflection roller 68 is arranged in the lower region of the device, over which a rope 70 is guided, which acts on the bear 64 at the end. With the aid of the rope 70, a considerable tensile stress can be applied to the bear 64, by means of which the driving in of the displacement tube 66 is accelerated. The bear 64 is preferably of the Type that the frequency and the amplitude can be changed, preferably by an optimization program such that the frequency and amplitude is selected at which the greatest feed per unit of time is achieved.

In Fig. 9 it can be seen how floor columns of the z. B. are shown in Fig. 4 arranged in a square grid. The columns are marked there with 72. The grid is indicated by dashed lines 74. As can also be seen, further columns 76 are each arranged centrally between four columns 72. The corresponding grid is indicated by a dot-dash line at 78. The columns 76 are pure sand columns, i. H. they are buried using a displacement or other pipe, but without the use of a geotextile covering. The floor pillars made of sand do not have the strength of the pillars 72, but they also contribute to the stabilization, in particular if they are introduced after the pillars 72 after the floor has already stabilized. With the aid of such a principle, a particularly economical procedure can be made possible if the soil strength is desired.

In Fig. 10 a dam 80 is shown, which is located on a relatively poor load-bearing floor 82. The dam 80 is to be widened, as is shown by the section 84. Floor columns 86 are introduced to stabilize the floor and to support the section 84, as is shown, for example, with reference to FIGS. 1 to 4. It can be seen that further floor columns 88 are introduced at an angle to the vertical, specifically in the region of the dam in which horizontal components occur due to the expansion. With the help of the inclined arrangement of the columns 88, these forces can be absorbed particularly well.

Claims

Expectations 1. A method for the production of floor columns for the removal of building and traffic loads, in which a tubular formwork is driven into the ground into a stable area, the soil material is removed from the tubular formwork, a casing made of geotextile material is inserted into the tubular formwork and is filled with load-bearing, granular, rolly material, the load-bearing material is then compacted and the tubular formwork is removed, characterized in that for each floor column, a single casing pipe is driven into the ground, the casing pipe is emptied by reaching out, a sack-like wrapping in the empty jacket tube is introduced, the diameter of which is larger than the inside diameter of the jacket tube and the granular material progressively presses the casing against the remaining base layer and the inner wall of the jacket tube when filling, ver the granular material when pulling out the jacket tube so far it is sealed that the covering is stretched beyond its original diameter to approximately equilibrium with the opposing forces generated by the surrounding soil, which is also compacted, the permeability of the material of the covering being such that essentially no surrounding soil penetrates into the column formed. 2. A method for the production of floor columns for the removal of building and traffic loads, in which a tubular formwork is driven into the ground into a stable area, a covering of geotextile material is inserted into the tubular formwork and filled with load-bearing, granular, rolled material, the load-bearing material is then compacted and the formwork is removed, characterized in that a single displacement pipe closed at the lower end by an opening to be opened is driven into the ground , a sack-like covering is introduced into the displacement pipe with a diameter approximately equal to or larger than the inside diameter of the displacement pipe, the granular material progressively presses the covering against the remaining lower support layer and the inner wall of the displacement pipe while the extraction pipe is pulled out while the displacement pipe is open the material is compacted below the tube end, the casing is stretched beyond its original diameter to approximately equilibrium with the counterforce generated by the compacted surrounding soil, the material The permeability of the casing is such that essentially no surrounding soil penetrates into the column formed. 3. The method according to claim 1 or 2, characterized in that a mixture of sand and bentonite is filled in the lower region of the envelope over a certain height. 4. The method according to claim 3, characterized in that the volume fraction of bentonite is 6 to 15%, preferably 8 to 12%. 5. The method according to any one of claims 2 to 4, characterized in that a drilling displacement tube is used and between the casing and a protective cover is arranged on the tube wall, preferably made of fleece. 6. The method according to any one of claims 1 to 5, characterized in that the covering is pushed onto an inner tube and frictionally attached to the inner tube at a distance from the upper end such that the covering when filling with the granular material and pulling up the inner tube on it Outside slips. 7. The method according to any one of claims 1 to 6, characterized in that a self-optimizing in the amplitude and frequency variable vibrator is used for driving the tube. 8. The method according to claim 7, characterized in that the vibrator is biased relative to the tube in the driving direction, preferably 20 to 25 t. 9. The method according to any one of claims 1 to 8, characterized in that in a first step geotextile-covered floor columns are introduced in a predetermined grid in the ground and in a second step a second grid only consisting of granular material floor columns are introduced into the ground are, the second floor columns are each arranged between the first. 10. The method according to any one of claims 1 to 9, characterized in that in the area with a significant horizontal component caused by the load, the floor columns are introduced at an angle to the vertical. 11. Envelope for performing the method according to one of claims 1 to 10, characterized in that it consists of a fabric or grid, optionally in combination with nonwoven. 12. Covering according to claim 11, characterized in that its short-term strength is 20 to 500 kN / m when using seams or 20 to 250 kN / m when using a seamless cover. 13. Covering according to one of claims 11 or 12, characterized in that it is formed from a web section of the geotextile material which is connected to one another at two edges in a special seam process. H. Cover according to claim 13, characterized in that the width of the vicinity is at least 1/5 of the column circumference. 15. Cover according to one of claims 11 to 14, characterized in that the warp threads (38) of the fabric (36) in the longitudinal direction of the cover and the weft threads (40) extend transversely thereto and zones of different strength are formed by closer or further spacing of the weft threads are. 16. Cover according to claim 15, characterized in that the weft threads (40) in the higher loaded area of the cover are narrower than in the area above or below. 17. Wrapping according to one of claims 11 to 16, characterized in that a second wrapping of limited length is drawn over a portion of the wrapping.