NL1010001C2 - Method and casing for the production of a ground column for absorbing the pressure of construction and traffic works. - 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

VO 2267

Title: Method and casing for the production of a ground column for absorbing the pressure of building traffic works.

The invention relates to a method for manufacturing a soil column for absorbing the pressure of construction and traffic works according to the preamble of claim 1.

DE-195 18 830 discloses a method for stabilizing the subsurface and for absorbing the pressure of construction and traffic works, in which a soil column of insufficient load-bearing material is removed in certain places and a hole is obtained in the hole obtained. sheathing of a pull-out, relatively tensile, filtering material is introduced. The casing is filled with granular material, which is compacted thereon, while at the same time the casing is widened such that the surrounding soil absorbs the horizontally directed forces through direct fixed contact. The casing consists of flat material, in particular of an armed or unarmed geotechnical fabric. The granular material is a hard grain-sized material, such as gravel sand, stone, crushed gravel, slag, mine tailings, recycled materials, and the like, to which polymeric or hydraulic acting binders may be added. The compacting of the introduced material is effected by shaking, vibrating or striking the tubular body, optionally with the aid of a pile driver or the like.

In this way soil with insufficient load-bearing capacity results in a material column which is particularly strong and which is arranged on the substrate which has a load-bearing capacity. The pressure of construction and traffic works is transferred on the one hand to the subsurface that has sufficient load-bearing capacity and, on the other hand, by power transfer to the surrounding ground. The surrounding 1010001 2 soil is also compacted and reinforced in the described method and is therefore also able to absorb horizontal forces.

For the manufacture of columns, the known method is carried out in such a way that a tubular body or jacket pipe is driven into the bottom and is subsequently emptied. Then, the casing, applied to an inner tube smaller in diameter, is introduced into the casing tube. The granular material is introduced into the inner tube, after which the jacket tube is then vibrated out of the ground under a compacting action, and subsequently also the inner tube. Although such a method gives satisfactory results, it is relatively expensive.

The object of the invention is therefore to provide a method for manufacturing a ground column for absorbing the pressure of construction and traffic works, wherein 1 can be operated at a lower cost and yet very good results are obtained.

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

In the invention it has been recognized that for erecting a soil column only a single tube is sufficient.

! In the solution of claim 1, a single jacketed pipe is driven into the ground and emptied in the usual manner. A bag-shaped casing of an extensible material is then introduced into the empty casing. The bag-shaped casing therefore hangs more or less deeply in the casing tube and has an irregular, not yet expanded, shape in the present case. However, by filling with a granular material, the bag-shaped casing can be lowered to the bottoms of the casing, which is formed by the load-bearing bottom layer. A further filling with granular material '35 results in that the bag-shaped envelope gradually comes to lie completely against the bottom and the wall of the jacket pipe 1010001 3. Optionally, a certain tension must always be provided at the top end of the bag-shaped casing, which protrudes from the top end of the jacket pipe, so that unnecessary deformations do not occur. Despite this tension, a certain amount of elongation must remain, so that a complete position of the casing against the bottom and the wall is guaranteed. Essential to the invention is that the casing has a larger diameter than the inner diameter of the casing tube. When the casing tube is pulled upwards from the bottom and a simultaneous compaction of the granular material in the envelope, an expansion of the column in the horizontal or radial direction also takes place, which column with an envelope not yet stretched has a larger diameter than 15 the inner section of the casing. The intensive compaction of the filling material further leads to an extension of the geotechnical fabric, whereby an additional horizontal widening of the soil column is obtained.

The described method results in a corresponding compaction of the surrounding soil, which has insufficient load-bearing capacity, until a force equilibrium is established between the horizontal forces transferred during compaction and the reaction forces generated in the surrounding soil, whereby part of the stresses generated by compaction created by the material of the enclosure. In this way, a column is obtained which guarantees good pressure relief from construction and traffic works, even with very weak and no load-bearing soil.

The method according to claim 2 also uses a single tube, which however is formed by a soil displacement tube. It is therefore provided with a seal during driving into the ground so that no soil can enter the interior of the soil displacement tube. It will be clear that when the casing pipe in claim 1 is used, its cross-section can be larger than 1010001 4 than with a soil displacement pipe. From an economic standpoint, soil displacement pipes can only be vibrated into the ground to a certain diameter.

Soil displacement pipes, the bottom end of which is closed by, for example, a valve, are known per se, for example from DE 296 11 427. Instead of a smooth displacement pipe which can be closed at the bottom end by a suitable seal, a pipe for a so-called drilling displacement process can also are used. A screw winding or the like is present with such a tube, so that a movement in the ground is obtained by a rotary movement. In such a method, the use of a vibrating device is not necessary. Pulling up of the tube after filling the casing can also be done by rotation.

In the method according to claim 2, the bag-shaped casing is introduced into the displacement tube, wherein the diameter of the bag-shaped casing corresponds approximately to or is also larger than the inner diameter s of the displacement tube. The way in which the enclosure comes to rest completely against the displacement tube is! similar to that described for claim 1. After filling with the granular material, the casing; comes to lie against the displacement tube, it follows compaction and possibly simultaneously with the vibration of the displacement tube, with the bottom end of which is then opened. When two roof-shaped flaps are fitted, this is done automatically. However, it is also possible to provide a so-called loss point, which remains in the ground when the displacement tube is pulled upwards.

The surrounding material is already compacted by driving the displacement tube. By compacting the granular material in the envelope, in particular when the displacement tube is pulled upwards, a further compaction takes place, to the extent that a balance is again obtained between the horizontal pressure of the column and the reaction forces of the surrounding soil. In this case, too, an effective pressure relief is thus obtained. In both cases, the columns obtained in this way are such that in the event of a horizontal deviation of parts of a column or by a spread of columns relative to each other, the column remains intact.

The soil columns obtained according to the method according to the invention are also used for sub-layers with a high groundwater level. There is then a danger that the groundwater will penetrate the columns under strong pressure. According to the invention, in order to produce a good soil column under such conditions, a mixture of sand and bentonite is introduced over a certain height into the lower region of the casing, for example with a volume share of 6 to 15% bentonite. Bentonite, as is known, has waterproofing properties. When water penetrates into column 20, a watertight plug is formed therein in the bottom region of the soil column, preventing further water penetration.

It has already been stated that a displacement tube can also be used for a drilling displacement process. During the pulling up of the displacement tube, the tube is rotated relative to the filled casing. In a special embodiment, a protective sleeve is provided between the displacement tube and the casing to protect it and not to weaken it, which can for instance consist of a fleece. The purpose of the fleece is only to protect the enclosure against mechanical damage during the upward movement of the displacement tube. After that it has no function.

Often the soil having insufficient load-bearing capacity, which has to be stabilized by means of soil columns, is located under a layer with sufficient load-bearing capacity, which is already present or has been applied later. In the manufacture of a soil column it is necessary to drive the pipe through this layer into the layer with insufficient load-bearing capacity, and this into the bottom layer with sufficient load-bearing capacity. On the other hand, it is sufficient that the soil column extends only over the layer having insufficient bearing capacity. However, if the casing is placed up to the top of the casing tube 10, more geotechnical fabric is used than is needed for the soil column. Hence, according to the invention, the casing is slid onto an inner tube and is in frictional contact with the inner tube at a distance from the top end, such that the casing when filling with the granular material and when pulling the inner tube upwards along the outside slips. In this method it can be ensured that the casing has only a length that is actually needed for the soil column. A considerable amount of geotechnical fabric is thus saved, which, due to the required tensile strength, is made with relatively high material and manufacturing costs. An inner tube has the further advantage that it can be provided with a funnel, via which the granular material can be introduced more easily into the envelope.

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Driving the tube in the method according to the invention preferably takes place by means of an shaking device which can be changed in amplitude and frequency, which additionally has the property of optimizing the driving process. When driving, the displacement is determined per unit of time and determines at which amplitude or frequency at which an optimum result is obtained. Since the manufacture of soil columns depends, among other things, on the speed with which the tube can be driven into the soil I, it is further advantageous to apply a pre-tension in the order of 20 to 25 t on the 1010001 7 shaker. It has been found that under such a bias the driving process can be considerably limited in time.

5 The cross section of the ground columns is of course determined by the cross section of the pipes in question. When driving pipes that are open at the bottom, a diameter of 1.2 to 1.5 m is possible. With a soil displacement pipe, the upper limit is 1 m in 10 cross-section. Tubes with a diameter of 80 cm are preferably used for this. Corresponding to this is the cross-section of the column of sand or other usable granular material surrounded by the geotechnical tissue. This in turn determines the strength of the improved soil, as it is obtained by arranging soil columns according to a predetermined pattern. It is also advantageous according to the invention if, after the introduction of soil columns with a geotechnical fabric according to the method described above, further soil columns are placed between the columns already introduced. These last columns consist only of sand; they do not have a geotechnical fabric enclosure. The introduction is effected in the same manner as described above for a tube that is open at the bottom or for a displacement tube and which is subsequently filled with suitably chosen granular material, preferably sand, and the tube being simultaneously compressed. is pulled up to form a sand column. Sand has the advantage that its volume hardly changes when the compaction takes place.

The last method described is advantageous in that a soil strength is achieved with a minimum of 35 soil columns with geotechnical tissue. The 1010001 8 manufacturing and material costs are therefore considerably reduced.

When erecting structures or constructing traffic roads, such as, for example, at a dam, it may happen that, for example, a widening also occurs a noticeable horizontal force component. It is true that the ground columns can absorb horizontal forces, but only to a certain extent. Hence, in a special embodiment according to the invention, the base columns are arranged at an angle to the vertical in the region of a noteworthy horizontal component. Such sloping ground columns are therefore more suitable for absorbing shear stresses. The skew is therefore in the direction in which the horizontal component is counteracted.

According to a further embodiment according to the invention, the envelope consists of a suitable geotechnical textile material, namely a fabric or braid, optionally in combination with a non-woven material.

It must have sufficient strength; for casings with a seam between 20 and 500 kN / m. As is known, a seam is a weakened place, so that the seam reduction factor is decisive for the measurement of the nominal strength. If, on the other hand, a seamless casing 25 is made, a material which has about half the required nominal strength of that of a seamed casing suffices. Preferably, a strength of at least 150 kN / m can be used with seamed casings and about half of them with seamlessly manufactured casings.

Preferably such seamless casings are used. In the other case, it is simplest: when the casing is made of a wide strip of the desired material, which is folded in half, after which the open edge is sealed by a special seam. Sealing: 1010001 9 is effected by interweaving the two ends or by a suitable seam material.

The load on the enclosure of geotechnical fabric in the height direction is not equal. It may therefore be advantageous to adapt the strength to the load. According to the invention it is possible to have the warp threads of the fabric extend in the longitudinal direction of the wrapping and the weft threads transversely thereto, zones of different strength being formed by a shorter or greater distance from the weft threads. If the weft threads are close to each other, the strength is clearly greater than if they are further apart. Another possibility is to draw a further casing with a limited length and also of a geotechnical fabric over the casing already present, whereby the strength is increased in that range.

An exemplary embodiment of the method according to the invention will be further elucidated with reference to the appended drawing. Herein shows:

Fig. 1-4 schematically various stages in the manufacture of a soil column according to the method according to the invention;

Fig. 5 a part of the fabric of an envelope for a soil column manufactured according to the invention;

Fig. 6 schematically introducing a casing into a tube located in the ground using an inner tube;

Fig. 7 schematically a soil displacement tube 30 for a drilling displacement process;

Fig. 8 schematically shaking a tube for the soil displacement process;

Fig. 9 schematically shows an arrangement of ground columns according to the invention; FIG. 10 schematically introducing soil columns for a dam widening.

10 100 0 1 10

Fig. 1 shows how a grain counting tube 10, which for example has a diameter of 1 m, is driven into a base layer 12; this base layer 12 consists of a non-load bearing material. The jacket pipe 10 is driven into a load-bearing base layer 14, for example 1.5 m, under the base layer 12. The jacket pipe 10, however, extends to a certain distance above the layer 12.

As further shown in Fig. 1, a bag-shaped casing 16 hangs in the tube 10, which has been emptied therefor by excavation to the level 20 formed by the load-bearing layer 14. With a completely open bag-shaped envelope 16, the cross-section! 15 thereof larger than the inner diameter of the jacket pipe 10, for example up to 10%. By lowering the casing 16, it hangs more or less deformed in the interior of the casing 10, with the top end 22 folded around the edge of the casing 10 and held by suitable means, for example, by a tension strap. Granular material, for example sand, as described in DE 195 18 830, I is then introduced. Inserting the first amount of it! results in the casing 16 being placed under a vertical tension, so that it can drop to level 20 by passing over the edge. A further filling with granular material results in the casing being pressed more and more against the bottom 20 and the wall of the casing tube 10, whereby by holding the top edge 22 of the casing 16 it is ensured that it is under more or less tension. The full filling of the casing tube when the casing 16 comes into contact simultaneously is shown in Fig. 2. The level of the inserted material 24 is approximately just below the top of the casing. · - · Λ f j 11 jacket pipe 10, at least above the level of the layer 12.

Fig. 3 shows how the casing tube 10 is pulled up in the direction of the arrow 26. This takes place under compaction of the introduced material 24. This compaction can be done either exclusively by vibrating the drawn up casing tube and / or by applying known compaction techniques. Because the casing 16 has a larger cross-section than the inner cross-section of the casing 10, this results in a corresponding expansion of the column formed in this way, whereby a further expansion in horizontal or radial direction occurs and whereby the material in gives the envelope 16 a characteristic yield according to its stress strain 15. After the casing tube 10 has been completely pulled up with the accompanying compaction, a soil column 28 is obtained, the upper end of which corresponds to the level of the layer 12. This soil column, together with other, not shown, 20 soil columns, which according to a determined cartridge, to absorb the pressure of construction and traffic works. It will be clear that a comparable bearing layer, for instance 1 to 1.5 m thick, could be applied to the stabilized base layer, which is not shown here.

It can be seen from Fig. 3 that due to the compaction of the material 24, a force is exerted on the surrounding material 12, indicated by the arrow 30. The surrounding material 12 is also compacted and builds up a reaction force 32. After the base column 28 has finally been applied, the forces 30, 32 are in equilibrium, whereby part of the force 30 can be absorbed by the tension in the casing 16.

When applying a soil column according to the soil displacement process, the same procedure is followed, but the tube is driven into the displacement process 12 in such a way that emptying of the tube is no longer necessary. In the displacement process, however, the tube has a smaller diameter than in the above-described method, for instance only up to 0.8 m.

In the lower region of the material 24, in Figs. 2-4, a kind of seal is indicated, which is obtained by a mixture of granular material, for instance sand and bentonite, the latter being added in a proportion of 6 to 15%. . It has the property that when water penetrates a swelling and | a compaction occurs, so that a further penetration of water, for instance groundwater, into the material of the column is prevented.

The casing for the soil column is preferably manufactured in an all-round process, so that seams, which by nature can be regarded as a weak point, are avoided. Suitable plastic materials are used that can withstand considerable loads up to 500 kN / m.

Preferably, a braided or woven structure 20 is used, which is such that it allows the passage of water, but not the passage of material to the surrounding soil. The filtering effect can be further improved by using built-in nonwoven material. Fig. 5 shows part of such an envelope. The warp threads 38 extend in the vertical direction, while the weft threads 40 extend in the horizontal direction. As can be seen from Fig. 5, the distance between the weft threads 40 in the vertical direction is different. As a result, a zone of increased strength can be obtained in the envelope.

The material of the casing is chosen such that it can absorb a considerable tensile force, but allows a certain stretch to compact the surrounding soil in order to build up a reaction force up to the equilibrium value. This process takes place relatively quickly.

Subsequent settings hardly ever occur.

1010001 13

As can be seen from Figures 1 and 2, the casing extends over the top end of the tube. In many cases, however, there is already a carrier layer with the appropriate condition above the bottom layer to be stabilized.

The tubular body must therefore first be passed through this layer and subsequently through the layer to be stabilized to the layer having a load-bearing capacity. On the other hand, the soil column should only extend over a height of the layer to be stabilized. The method described with reference to Figures 1 and 2 therefore consumes a larger amount of geotechnical tissue than is necessary in the latter case. Fig. 6 now shows how the tube 10 according to Figs. 1 and 2 has been driven through a carrier layer 42 present on the layer 12 to be stabilized. The bottom end of the tube 10 is not shown. As further indicated, an inner tube 44 is provided, over which the casing 16 is drawn, so that the casing 16 can be introduced into the tube 10 with the inner tube 44. The special feature is that the top end of the casing 16 is arranged at a distance from the top end of the inner tube 44 on the outside, for instance with a tensioning strap 46 or the like. In the final state, the envelope therefore only extends to the top of the layer 12 to be stabilized. The inner tube 44 is provided at the top end with a funnel 48 through which the granular material can be introduced. At the same time as filling, the inner tube 44 is pulled up, but the casing 16 remains in place. The fastener 46 forms only a frictional contact and slides over the inner tube 44 as it is pulled out. After the casing 16 has been completely filled, as indicated in Figs. 2-4, the tube 10 can be removed in the manner already described and with the aid of shaking means or the like.

10) 0001 14

Fig. 7 shows a drill displacement tube 50, which has a kind of screw winding 52 on the outside for penetration into the ground. The pipe 50 can again have a suitable seal at the bottom end, which is closed when it is turned into the ground, but is opened when it is turned upwards. As will further be apparent from Fig. 7, a casing 54 has been introduced in a manner as already described with reference to Fig. 1. The casing can be | have an inner cross-section corresponding to or larger than the inner cross-section of the tube 50. Between the casing 54, which can be further constructed as the casing 16, and the wall of the tube, a non-woven layer 56 is provided. This fleece layer serves to protect the enclosure 54 filled with granular material when the tube 50 is rotated out of the ground.

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Fig. 8 schematically shows a shaking device 60, which, via a cable 62, carries a drop block 64 from which a displacement tube 66 is suspended. It is further indicated that in the lower region of the device there is a return pulley 68, over which a cable 70 is passed, which is connected at the end to the drop block 64. With the aid of the cable 70, a considerable tensile stress can thus be transmitted to the drop block 64, whereby the displacement of the displacement tube 66 is accelerated. The drop block 64 is preferably of the type in which the frequency and amplitude are changeable, for example, by an optimization program, such that that frequency and amplitude are selected with the greatest downward movement per unit time.

Fig. 9 shows how ground columns of, for example, the type shown in Fig. 4 are arranged in a square grid pattern. The columns are indicated by 72 therein. The grid is indicated by broken lines 74. As will further appear, the further columns 76 are each arranged centrally between four columns 72). The associated grid pattern is indicated by 78. Columns 76 are pure sand columns, ie they are placed in the ground by means of a displacement tube or other tube, without using a geotechnical fabric. While the sand base columns do not have the strength of the columns 72, they do contribute to stabilization, especially when introduced after some time after columns 72, after the soil has already undergone stabilization. Such a principle makes a particularly economical way of working possible for a desired soil strength.

In Fig. 10 a dam 80 is shown, which is located on ground with a relatively low load-bearing capacity. The dam 80 must be widened, as indicated by the section 84. Soil columns 86 are provided to stabilize the ground and to support the section 84, as explained with reference to Figs. 1-4. It can further be seen that ground columns 88 are arranged at an angle to the vertical at 20 in the region of the dam in which horizontal components occur as a result of the extension. With the aid of an inclination of the columns 88, they can thereby absorb these forces particularly well.

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Claims (17)

1. A method of manufacturing ground columns to absorb the pressure of construction and traffic works, in which a casing is driven into the ground to a distance where this pipe is fixed, then the ground material is removed from the casing , a casing of a geotechnical textile material is introduced into the jacket pipe, which is filled with a load-bearing, granular material, which is then compacted, after which the jacket pipe is removed, characterized in that for each column of soil a single jacket pipe in the ground is driven, a bag-shaped casing is introduced into the empty casing tube, the bag-shaped casing of which the diameter is greater than the inner diameter of the casing tube and the granular material, during filling, increasingly the casing against the remaining support shaft and the inner wall of the casing. jacket pipe, the granular material when removing the jacket Each tube is compacted to such an extent that the casing expands further beyond its original diameter 20 until a corresponding counterweight is created with the reaction forces generated by the likewise compacted soil, the material of the casing being so permeable that substantially no surrounding soil in the column formed penetrates. 2. A method of manufacturing ground columns to absorb the pressure of construction and traffic works, in which: a casing is driven into the ground to a distance at which it is fixed, a casing of a geotechnical textile material in the tubular body is filled with a load-bearing, granular material which is then compacted, after which the casing is removed, characterized in that a single displacement tube closed at the bottom end by a seal to be opened is driven into the ground as a casing 1010001 a bag-shaped casing is introduced into the displacement tube, the bag-shaped casing having a diameter equal to or greater than the inner diameter of the displacement tube, the granular material increasingly filling the casing against the retaining support shaft and the inner wall of the displacement tube, while leaving If the displacement tube is opened at an open lower tube end, the material is compacted, the envelope further expanding outside its original cross-section until a corresponding counterweight is created with the reaction forces generated by the likewise compacted soil, whereby the material of the envelope is so permeable. it is designed that substantially no surrounding soil penetrates into the formed column. Method according to claim 1 or 2, characterized in that a mixture of sand and bentonite is introduced over a certain height in the lower region of the envelope. 4. Process according to claim 3, characterized in that the volume proportion of bentonite is 6 to 15%, preferably 8 to 12%. Method according to any one of claims 2-4, characterized in that a drilling displacement tube is used and a protective sleeve, preferably made of fleece, is arranged between the casing and the wall of the tube. 6. A method according to any one of the preceding claims, characterized in that the casing is slid onto an inner tube and is in frictional contact with the inner tube at a distance from the top end, such that the casing when filled with the granular material and sliding up the inner tube along the outside. Method according to any one of the preceding claims, characterized in that a 1010001 self-optimizing amplitude and frequency-changeable shaker is used for driving the tube. 8. A method according to claim 7, characterized in that a bias is applied opposite the tube in the driving direction, preferably in the order of 20 to 25 t. 9. A method according to any one of the preceding claims, characterized in that in a first step soil columns surrounded by a geotechnical textile material are introduced into the ground according to a predetermined pattern and in a second step only soil columns consisting of granular material according to a second pattern in the i! ground, the second soil columns J each being arranged between the first. Method according to any one of the preceding claims, characterized in that in the region of a noteworthy horizontal force component caused by the load, the ground columns are introduced at an angle to the vertical. 11. Casing for carrying out the method according to any one of the preceding claims, characterized in that it consists of a fabric or braid, optionally together with a nonwoven material. J Enclosure according to claim 11, characterized in that: the nominal strength when using seams from 20 to 1! 500 kN / m or when using a seamless casing i from 20 to 250 kN / m. t 13. Casing according to claim 11 or 12, characterized in that it consists of a strip of geotechnical fabric which is joined together at two edges by a special seam connection. Casing according to claim 13, characterized in that the width of the seams is at least 1/5 of the column size. Casing according to any one of claims 11-14, characterized in that the warp threads (38) of the fabric (36) extend in the length of the casing and the weft threads (40) transversely thereto and zones of different strength are formed by a smaller or larger distance between the weft threads. Casing according to claim 15, characterized in that the weft threads (40) are closer together in a higher loaded area of the casing than in the area above and below. 17. Casing according to any one of claims 11-16, characterized in that a further casing with a limited length is pulled over a part of the casing already present. iC'K ·· .. ·;