EP1234916B1 - Method for making column members - Google Patents

Abstract

Process for producing columns in ground having at least one unstable ground layer comprises shaking a displacement device (17) from the ground surface (11) through a non-supporting ground layer up to a supported ground layer (13, 14), constructing a lower column section (20) supported by the supported ground layer, inserting a tubular sleeve (22) from the ground surface into the lower column section, and filling the sleeve with material to form an upper column section supported by the sleeve. Independent claims are also included for a column body and an improved/stabilized building ground in which column bodies are distributed. Preferred Features: The material used to fill the upper column section is made from sand, water, concrete, stone, ballast, or gravel. The sleeve is made from a steel sheet, composite material or plastic.

Description

The invention relates to a method for producing columns in soils with at least one non-load-bearing bottom layer for the purpose of ground improvement or stabilization. There are a variety of methods are known, according to which insufficiently sustainable ground is improved by the incorporation of columns arranged in a grid. Here are different mechanisms of action to advantage. On the one hand can be done by deep-reaching columnar body load transfer into deeper-lying viable layers; In addition, by incorporating the columnar body without prior excavation, a soil compaction between the column bodies can take place; Finally, when using dry binder in the column bodies soil water can be extracted from cohesive soils.

For cost and procedural reasons are favorable uncased columns, which can be constructed in a continuous operation on a pedestal in stuffing or vibrating by means of deep vibrators with lock tube. This manufacturing technique comes to its limits or fails in the presence of soft layers that can not build sufficient radial support forces to hold the column body when loaded by loading dimensionally stable, called in the following non-sustainable soil layers.

From DE 44 08 173 A1 and EP 0 900 883 A1 it is known to provide column bodies which extend into a load-bearing bottom layer, with an envelope made of a tube or a geotextile material, wherein first an excavation or a displacement of the soil takes place and then wrapping and filling material are introduced. For very low-lying, load-bearing layers, the process requiring temporary piping is too expensive.

On this basis, the invention has for its object to propose a method for the production of columns, which leads to time-consuming and cost advantages in the application of low-lying viable or at least supportive layers and non-sustainable surface layers or intermediate layers. The solution to this problem consists in a method for producing columns in soils with at least one non-load-bearing bottom layer for the purpose of ground improvement or stabilization, with the following method steps for producing one of the columns, a displacement device, in particular a deep vibrator with lock tube or a displacement tube with closure, is vibrated from the bottom surface through the at least one non-viable bottom layer into a viable or at least sustainable soil layer, a directly supported by an at least supportable bottom layers lower column section, in particular by means of the displacement device, from bottom to top of rolling material constructed, a tubular or tubular casing is from the bottom surface, at least one non-sustainable bottom layer passing through, built into the lower column section extends in sufficient depth, the envelope is zum Bildu ng of an upper supported by the sheath Column section filled with rolling material. This is compacted in the cladding.

In a favorable development, in particular in the presence of load-bearing soil layers, a thickened column foot of rolligem material, in particular by means of the displacement device, first installed in the load-bearing soil layer on which then the lower column section is constructed.

The main advantage of the method is therefore to use as far as possible in conventional stuffing or vibrating produced uncased column body, which can rest on a particular embedded in a stable or at least supportive layer thickened column base, and the stability of the column body by using a sheath exclusively to a depth from which there is sufficient continuous support capability down to the lower end of the column. The present stratification is to be determined by previous excavation drilling or other foundation exploration methods.

The columns according to the invention are characterized even with the use of binder-free material even with the expected loads thereby dimensionally stable, that the envelope in the unstable floor area is designed so that it absorbs the expected stress conditions with minimal radial deformation and thus the loads in the un-threatened lower column section and the pedestal can be registered without damage.

After a first process implementation, the envelope after a first shaking and pulling the displacer - after production of the lower column section - at the coaxially mounted on the lower end of this and drilled at a second shaking the displacement device to its intended depth. The process sequence is in this case initially the same as in the production of conventional vibrating or Stopfsäulen, which as already mentioned, when pulling the lower column section is made only zoom up to a first soft layer and the displacement device is then pulled to leave a displacement hole. In this case, the introduction of support liquid may be required. Thereafter, the envelope is mounted on the displacement device and drawn in a second additional shaking with this in the existing open Rüttelöffnung and partially introduced into the existing lower column section. Thereafter, the displacer can be drawn by immediately filling the casing and compacting the filler material (contractor method) or drawing it without introducing filler material, which can then be filled from the top end of the casing (from the bottom surface).

According to a second simplified procedure, the casing is mounted at a distance from the lower end of the displacer coaxially on this and already at a first shaking of the displacement device - made before the production of the lower column section - with this and separated while pulling from this. The latter separation can be done automatically, if in one direction effective entrainment means are used. Also, special coupling means separable from the ground surface may be provided. In this process, the enclosure is brought to the intended depth, so that it extends down to at least sustainable soil layers. When pulling the displacement device, the material of the column can be introduced in a single operation from bottom to top be carried out, wherein in the upper region, the radial support is carried out by the already installed sheath. Accelerated pulling of the displacement device in the region of the enclosure and filling of filling material in the upper column section from the bottom surface is here less sensible, but not excluded.

The use of binderless, mobile material - rock, gravel, gravel, sand - is appropriate in those cases where the columns are also said to have vertical drainage, i. when water permeability in the vertical direction is to be guaranteed, or in which the same is not disadvantageous.

In other cases, the use of binder-containing rolligem material - mortar, concrete - is preferable, especially when higher loads are to be removed and / or water exchange between different water-bearing layers is to be avoided.

When wrapping come substantially dimensionally stable tubular body, whether without breakthroughs, be it with breakthroughs, from the known materials such as steel, composite material or plastic into consideration. According to another approach, a geotextile tube, be it with nonwoven composite portion or without fleece portion, can be used as the sheathing. In this case, a necessary radial stress state in the column body arises only as a result of a significant radial expansion of the hose body. The tube sheaths used are usually designed as open-bottom tube. When using geotextiles, the use of closed-bottom hoses may be more convenient for easier downsizing.

The present invention finds application wherever the displacement or compaction of the soil during the introduction of stuffing or vibrating columns, the required support stress or reaction stress in upper soil layers - surface layers or intermediate layers - is not achieved and the soil for the functionality of the column required radial support can not build up or a horizontal running of the mortar or concrete during insertion before its hardening can not prevent.

In the lying directly above the lower end of the column soil layers in which there is sufficient radial support throughout, the column is prepared according to known techniques without additional coating.

In the area of the load application over the lower column section, a sufficiently load-bearing or at least supportable layer must be present, in which initially a pedestal can be stuffed out of roll-like material. Usually gravel, gravel, sand, mortar or concrete, d. H. case-hardened material with or without addition of binder is used.

By using binder-containing material, a vertical flow can be reduced or prevented, so that a connection between different groundwater floors remains suppressed.

In upper soil layers - surface layers or intermediate layers - in which a sufficient radial support of the column is not guaranteed, the column is according to the invention with a covering made of tubes or geotextile tubes.

The upper pillar portion (with wrapper) can be filled and stuffed with coarse material with or without binder additive, usually gravel, crushed stone, sand, mortar or concrete, regardless of the embodiment of the lower pillar portion (without wrapper).

If an envelope is used made of a material that undergoes significant elongation during load application, so in particular in a geotextile envelope, it is advantageous to compress the filler in the envelope immediately during column production, so that no significant additional strains occur during load application and only construction-compatible settlements are to be accepted later.

In soil layers in which for uncased columns, z. B. Schottersäulen, mortared Stopfsäulen, Fertigmörtelstopfsäulen, Betonrüttelsäulen, required support voltages can not be permanently generated by displacement and compression of the surrounding soil, d. H. in which the soil contributes only slightly to the radial support stress, it must therefore be applied to a substantial extent by the circumferential expansion of the envelope during introduction of the filling material.

The wrapper may additionally serve to prevent or substantially prevent a change or chemical reaction of the column material with the soil, the soil moisture, the groundwater, for example, to reduce or completely avoid a change in the pH in the surrounding soil by the introduction of binder.

With the method according to the invention viable columns can be prepared, which can be charged immediately or after hardening of the binder optionally used. Due to their method of manufacture, only small settlements are expected when applying loads.

Figur 1

zeigt ein erstes, zweistufiges erfindungsgemäßes Verfahren zur Herstellung von Säulen unter Verwendung einer Rohrumhüllung;

Figur 2

zeigt ein zweites, zweistufiges erfindungsgemäßes verfahren unter Verwendung einer Geotextilumhüllung;

Figur 3

zeigt ein drittes, einstufiges erfindungsgemäßes Verfahren unter Verwendung einer Rohrumhüllung;

Figur 4

zeigt ein viertes, einstufiges erfindungsgemäßes Verfahrend unter Verwendung einer Geotextilumhüllung.

Before the construction of the ground to be improved, a detailed soil excavation is required; In particular, to determine the required length of the enclosures are preferably carried out in a narrow grid pressure probes with which the transition from non-sustainable soil layers to supportive or sustainable soil layers is determined. The lower boundary layer of the lowest unsupportable soil layer determines the depth of the sheath, the supporting and load-bearing soil layers need not be distinguished substantially. The method is readily applicable if only non-sustainable soil layers contain soil layers that are well-supported. However, it is mutatis mutandis applicable if under the non-sustainable soil layers only at least sustainable soil layers are located and the columns in this area are sufficiently deep to cause a load transfer mainly on skin friction.

FIG. 1

shows a first, two-step process according to the invention for the production of columns using a pipe jacket;

FIG. 2

shows a second, two-stage process according to the invention using a geotextile sheath;

FIG. 3

shows a third, one-step process according to the invention using a pipe jacket;

FIG. 4

shows a fourth, one-step process according to the invention using a geotextile wrapper.

FIG. 1 shows in four phases a) to d) the preparation of a column according to the invention. A vertically cut ground with the surface 11 has a non-load-bearing and unsupportable upper soil layer 12 (soft layer), including an at least supportable soil layer 13 and finally including a well-soil layer 14th

In the representation a) a brought on the surface 11 in position caterpillar 15 is shown in the erected leader 16, a vibrator 17 is guided, which passes through a feed hopper 18 for material introduction. The Rüttlerspitze is shaken to the viable soil layer 14. Dashed lines show a thickened column foot 19, which can optionally be produced in a first step by vibratory compaction or stuffing compaction of a rolling material, with or without binder aggregate.

In the representation b) the vibrator 17 is already fully drawn, wherein - on the optionally existing column foot 19 - in vibrating or stuffing a lower column section 20 is made of rolligem material that extends into the viable bottom layer 14 and radially directly from the bottom of supportive soil layer 13 is supported. This lower column section 20 protrudes slightly into the unsupportable upper bottom layer 12, while otherwise the displacement hole 21 can be seen in this bottom layer. On the lower end of the vibrator 17, a tube 22 is coaxial mounted, which has inner driver 24 at the lower end, which can be taken by driving pin 23 at the bottom of the vibrator.

In illustration c) it is shown that the vibrator 17 and with it the sheath tube 22 in a second Einrüttelvorgang into the upper end of the lower column section 20, d. H. in particular are introduced into reaching into the at least sustainable bottom layer 13. The lower column section 20 has thereby obtained an upper thickening 25.

In the illustration d) it is shown that in the final pulling of the vibrator 17, the sheath tube 22 has been filled via the vibrator with rolling material, which may be compacted to a suitable extent, whereby an upper column portion 26 is formed with the radial support by the sheath tube 22 , Instead of the downwardly open sheath tube 22 used here, a tube closed at the bottom by a lid could also be set in the lower column section 20.

In Figure 2, the same details as in Figure 1 are given the same reference numerals, the process sequence of the column production is largely similar to that shown in Figure 1 in single steps. On the local description reference is made in this regard.

Deviating, however, according to representation b) not a downwardly open casing tube, but a closed bottom tube 27 made of geotextile in the second Einrüttelvorgang by vibrator 17 is fed into the Rüttelloch 21.

The result of this Einrüttelvorganges can be seen in representation c), in which case the envelope 27 has penetrated into the lower column section 20 and has caused a broadening 25 on the head.

As shown in illustration d), the geotextile tube 27 is filled with rolling material to form an upper column section 28, whereby the tube 27 can build up supporting forces by radial expansion and delimits the filling material essentially against the pending floor.

In FIG. 3, substantially the same device situation and the same bottom layering as in FIGS. 1 and 2 are shown in three phases. The same details are provided with the same reference numerals. On the local description reference is made in this regard. In this case, however, a fixed wrapping tube 22 'already during the first Einrüttelvorgang the vibrator 17 as shown a) with distance from the Rüttlerspitze coaxially pushed onto the vibrator and drilled in the ground. The corresponding entrainment means 23, 24 are in this case at a corresponding distance from the Rüttlerspitze. Again, a thickened column foot 19 is shown with dashed lines, which may optionally be constructed in the load-bearing bottom layer 14. The wrapping tube 22 'has already reached its intended position, which penetrates the non-sustainable bottom layer 12 and projects into the at least supportable bottom layer 13.

In illustration b), the vibrator 17 is already retracted into the interior of the casing tube 22 ', after it has produced a lower column section 20 in the region of the at least supportable bottom layer 13, which is supported radially directly from the bottom.

In the illustration c), the vibrator 17 is completely pulled out of the casing tube 22 'upwards, wherein the casing tube 22' is filled with rolling material to form an upper column portion 28, which here differs from the material of the lower column portion 20.

FIG. 4 shows essentially the same terrain and device situation and the same sequence of processes as in FIG. The same details are provided with the same reference numerals. Reference is made to the description of FIG. 3 in this respect. Instead of a rigid cladding tube here is a less visible geotextile below open geotextile 27 'pulled over the central portion of the vibrator 17 and taken down so far that it penetrates the non-sustainable bottom layer 12 and protrudes with the lower end in the at least supportable bottom layer 13. The column foot 19 is already completed in the area of the load-bearing bottom layer 14.

According to illustration b), when the vibrator 17 is pulled, the lower column section 20, which here consists of the same material as the pedestal 19, is produced, which is radially supported directly in the lower bottom layer 13.

According to illustration c), after complete pulling of the vibrator 17, an upper column section 28 which builds up on the lower column section 20 is formed by filling in the geotextile tube 27 'again with the same material. The radial supporting forces for the filling material are generated as a result of a radial widening of the sheath tube 27 '.

In the representations, the common principle can be seen that takes place to cheapen and reduce the material consumption an additional envelope for the column material only in the area not at least supportive upper soil layers. This reduces the need for supporting bodies by length meters as well as the consumption of filling material in the area of non-sustainable layers. The load transfer takes place over the entire column body in the lower soil layers inside, where in the region of the lower column section load transfer on skin friction in addition to the support load of the column foot or as an exclusive force into the ground is possible.

Claims (17)

1. A process of producing columns in soils with at least one non-load-bearing soil layer, for the purpose of improving the soil and, respectively, stabilising the soil, comprising the following process stages of producing one of the columns:

   a displacement implement (17), more particularly a depth vibrator with a bottom feed pipe or

   a displacement pipe with a closure, is vibrated from the soil surface (11) through the at least one non-load-bearing soil layer as far as and into a soil layer (13, 14) which is capable of bearing loads or at least capable of providing support;

   a lower column portion (20) supported directly by a soil layer (13, 14) which is at least capable of providing support is built up from below to the top from granular material, more particularly by means of the displacement implement (17);

   a pipe- or hose-shaped envelope (22, 27) is built in from the soil surface (11), passing through at least one non-load-bearing soil layer, until it reaches the lower column portion (20);

   for the purpose of forming an upper column portion (26, 28) supported by the envelope (22, 27), the envelope (22, 27) is filled with an granular material.
2. A process according to claim 1,
   characterised in
   that first a thickened column base (19) consisting of an granular material is built into the soil layer (13, 14) which is capable of bearing loads or is at least capable of providing support, on which column base (19) the lower column portion (20) is then built up.
3. A process according to any one of claims 1 or 2,
   characterised in
   that after a first vibrating-in operation and after the displacement implement (17) has been lifted following the production of the lower column portion, the envelope (22, 27) is coaxially fixed to the lower end of said displacement implement (17) and when the displacement implement (17) is vibrated-in for the second time, said envelope is lowered to its predetermined depth.
4. A process according to any one of claims 1 or 2,
   characterised in
   that the envelope (22, 27), at a distance from the lower end of the displacement implement (17), is coaxially fixed to same and when the displacement implement (17) is vibrated-in for the first time in advance of the production of the lower column portion, said envelope is lowered and, during the lifting operation, separates therefrom or is separated therefrom.
5. A process according to any one of claims 1 to 4,
   characterised in
   that use is made of a bonding-agent-free granular material - rock, broken stone, gravel, sand.
6. A process according to any one of claims 1 to 4,
   characterised in
   that use is made of a bonding-agent containing granular material such as mortar, concrete.
7. A process according to any one of claims 1 to 6,
   characterised in
   that the envelope is provided in the form of a tubular member (22) - without apertures, with apertures; consisting of steel plate, of a composite material, of plastics.
8. A process according to any one of claims 1 to 7,
   characterised in
   that the envelope is provided in the form of a geo-textile hose (27) - with a percentage of non-woven fabric; without a percentage of non-woven fabric.
9. A process according to any one of claims 7 or 8,
   characterised in
   that use is made of an envelope (22, 27) which is closed at its bottom end.
10. A column member in the soil for improving and, respectively, stabilising soils, produced in accordance with a process according to any one of claims 1 to 9, comprising
    an uncased lower column portion (20) which is built into soil layers (13, 14) which are capable of bearing loads or at least capable of providing radial support;
    an upper column portion (26, 28) which is provided with an envelope (22, 27), which passes through at least one non-supporting soil layer (12) and, by means of its envelope (22, 27), extends into the lower column portion (20).
11. A column member according to claim 10,
    characterised by
    a column base (19) which is embedded in a soil layer (13, 14) which is capable of bearing loads or which is at least capable of providing support and on which the lower column portion (20) is built up.
12. A column member according to any one of claims 10 or 11,
    characterised in
    that use is made of a bonding-agent - free granular material - rock, broken stone, gravel, sand.
13. A column member according to any one of claims 10 or 11,
    characterised in
    that use is made of a bonding-agent-containing granular material - mortar, concrete.
14. A column member according to any one of claims 10 to 13,
    characterised in
    that the envelope is used in the form of a tubular member (22) - without apertures, with apertures; consisting of steel plate, of composite material, of plastics.
15. A column member according to any one of claims 10 to 13,
    characterised in
    that the envelope is provided in the form of a geo-textile hose (27) - with a non-woven fabric filling, without a non-woven fabric percentage.
16. A column member according to any one of claims 10 to 15,
    characterised in
    that use is made of an envelope (22, 27) which is closed at its bottom end.
17. An improved and, respectively, stabilised soil in which column members according to any one of claims 10 to 16 are arranged so as to be distributed in accordance with a surface grid.

Images