EP1688543B1 - Soil improvement using hybrid piles - Google Patents

Description

The invention relates to a method for ground improvement for the construction of foundations by placing columns in the ground, which are distributed over the surface according to a grid and each a lower set tied column section of settable material such as mortar or concrete and a respective upper compacted column section of rolligem Have material like gravel.

Columns of this type are described, for example, in Sondermann, Wolfgang, Jebe, Walter: Ground improvement methods for the construction and upgrading of railway lines on high-speed lines, ground floor meeting 1996, Berl in. Here, the lower column sections are executed with sluice vibrators as Rüttelsäulen or compaction columns. As a rule, a gravel base is first produced in which the column is adjusted.

From the DE 101 08 602 A1 a method for the production of soil columns for ground improvement is known, in which different phases of the process are to be distinguished, which lead to at least two, possibly to three mutually distinguishable column sections. The bottom pillars may optionally have a thickened pillar base made of a rolled material with or without added binder. As essential components, the bottom columns comprise a lower column section, which is optionally supported on the pedestal and which is produced free in the growing ground from bottom to top of rolligem material, and an upper column section, the first of the completion of the lower column section introduced from enclosure a tubular body or a Geotextilschlauch, which is filled from bottom to top with rolling material, wherein the envelope extends into the lower column section. The rolling material of the soil column can be used with or without binder additive.

From the GB 515 120 is a generic method for producing piles in the ground by means of sinker known in which a concrete pile receives a head of moist compacted sand. The sand serves exclusively as a transfer medium in mechanically compacting the concrete within an upper soil layer with low shear resistance.

From the WO 02 077 136 A2 For example, there is known a foundation improvement method for building foundations in which pillars of resilient concrete are produced in a layer of low bearing capacity, which at the top freely terminate approximately centrally in a bulk material load-bearing layer of cellular material. On this load transfer layer, a foundation plate or individual foundations is constructed at a distance from the pile heads.

The present invention has for its object to provide a method for ground improvement of the type mentioned for the construction of foundations, with the fast and inexpensive the desired improvements can be brought about, the method should be easy to carry out. The solution of claim 1 for this is that for the preparation of the lower column section introduced a hollow tool displacing the soil and the abbindbare material is introduced when pulling the hollow tool out of this in the borehole, directly on the heads of the columns single or Streifenfundamente or a foundation plate to be built. In this case, the settable material, ie mortar or concrete, in particular discharged substantially without pressure when pulling the hollow tool into the borehole.

Thus, the lower column section consists of a Vollverdrängerersäule, in the production of no grown soil is excavated or rinsed, while the upper column section is produced as Rüttelsäule of rolligem, in particular binder-free material. Here, the diameter of the upper column section preferably considerably larger than the diameter of the lower column section. The upper column section can be led to the lower edge of the foundation of a building to be built. The main advantage of these hybrid floor columns is that the upper, relatively short column section can reduce stresses in the foundation plate and thus allows a reduced reinforcement of the same.

According to a first preferred method, the use of a rotary drilling tool with a load is provided for producing the lower column section. According to a second preferred method, the production of the lower column section is provided using a Senkrohres with a Aufsatzrüttler. With both methods, the tool can be lowered quickly, even in unfavorable soil conditions, which is superior to the relatively lower shaking speed of deep vibrators. The drill pipe or the sinker can already be filled in advance with the curable material, so that the borehole is filled for the lower column section without further preparation measures when pulling the tube. Due to the mere displacement during the production of the borehole, an initial ground improvement by soil compaction is already being created. The lower column sections allow the structural loads to be removed into load-bearing layers, while the upper column sections can absorb the shear forces without damage. Between the lower pillar portion and the upper pillar portion, a covering or bonding area is formed when the rolling material of the upper pillar portion partially penetrates into the not yet set material of the lower pillar portion. The coverage area may be on the order of 0.5 m.

Suitable diameters for the hollow tools corresponding to the diameters for the borehole of the lower column section are approximately between 200 and 600 mm.

For producing the upper column section, as is known per se, a deep vibrator is shaken up into the head region of the lower column section and then drawn with the application of rolled material. Here, by stepwise pulling and stopping the rolling material of the upper column section to the column head be compacted. It should be used gravel or gravel.

According to a first embodiment, it is provided that individual or strip foundations are produced directly on the column heads, wherein spaces between individual foundations are filled by a Fudamentplatte.

According to a second embodiment, it is provided that between the heads of individual columns, first a compacted leveling layer is produced, on which then a foundation plate is produced. The said leveling layer can also be produced in advance before the beginning of the column production, with the column heads then being pulled to the upper edge of the leveling layer. The underlying foundation plate thus rests on the column heads and the intermediate leveling layer. The grid, by which the columns are distributed over the surface of the ground, can be chosen according to the extent of the required ground improvement, for example, grid dimensions of 2, 3 or 4 m represent realistic sizes. The depth of the individual columns can be up to about 20 m, the upper column section being relatively short in comparison with the lower column section.

Essential for the described method is the production of the holes by pure displacement, with a hollow drill pipe or a countersink with Aufsatzrüttler is used for fast operation. The columns, which are made in two sections, do without a special pedestal (gravel foot), but with their lower column section they are founding directly in load-bearing soil layers. The columns can be stabilized by individual foundations on the column heads or by an intermediate layer between the column heads with each other, d. H. vaulted be expanded.

The lower column sections are not reinforced and thus fast and easy to produce.

• Figur 1 zeigt einen erfindungsgemäß verbesserten Baugrund mit einem Streifenfundament im Vertikalschnitt durch zwei Säulen;
• Figur 2 zeigt einen erfindungsgemäß verbesserten Baugrund mit einer Fundamentplatte im Vertikalschnitt durch zwei Säulen;
• Figur 3 zeigt ein erfindungsgemäßes Verfahren zur Herstellung einer Säule
  1. a) die Herstellungsphase 1 des unteren Säulenabschnitts
     1. 1. Aufbau des Geräts
     2. 2. Niederbringen eines Bohrrohres
     3. 3. Ziehen des Bohrrohres unter Ausfließen von Mörtel
  2. b) die Herstellungsphase 2 zur Herstellung des oberen Säulenabschnitts
     • 4. Einrütteln eines Tiefenrüttlers
     • 5. Fertigstellen des oberen Säulenabschnitts aus Schotter
  3. c) das Bohrrohr nach Phase 1 als vergrößerte Einzelheit;
• Figur 4 zeigt ein erfindungsgemäßes Verfahren zur Herstellung einer Säule
  1. a) die Herstellungsphase 1 des unteren Säulenabschnitts
     1. 1. Aufbau des Geräts
     2. 2. Niederrütteln eines Senkrohres
     3. 3. Ziehen des Senkrohres unter Ausfließen von Mörtel
  2. b) die Herstellungsphase 2 zur Herstellung des oberen Säulenabschnitts
     • 4. Einrütteln eines Tiefenrüttlers
     • 5. Fertigstellen des oberen Säulenabschnitts aus Schotter
  3. c) das Senkrohr nach Phase 1 als vergrößerte Einzelheit;

Preferred embodiments of the invention are illustrated in the drawings and described below.

• FIG. 1 shows an improved ground according to the invention with a strip foundation in vertical section through two columns;
• FIG. 2 shows an improved ground according to the invention with a foundation plate in vertical section through two columns;
• FIG. 3 shows a process according to the invention for the preparation of a column
  1. a) the production phase 1 of the lower column section
     1. 1. Structure of the device
     2. 2. Lowering a drill pipe
     3. 3. Pull the drill pipe with mortar
  2. b) the manufacturing phase 2 for the preparation of the upper column section
     • 4. Start shaking a deep vibrator
     • 5. Completion of the upper column section of ballast
  3. c) the drill pipe after phase 1 as an enlarged detail;
• FIG. 4 shows a process according to the invention for the preparation of a column
  1. a) the production phase 1 of the lower column section
     1. 1. Structure of the device
     2. 2. Lowering a sinker
     3. 3. Pull the Senkrohres under flow of mortar
  2. b) the manufacturing phase 2 for the preparation of the upper column section
     • 4. Start shaking a deep vibrator
     • 5. Completion of the upper column section of ballast
  3. c) the Senkrohr after phase 1 as an enlarged detail;

In FIG. 1 For example, in a vertical bottom section, two similar columns 11 are shown, each comprising a lower column section 12 of cured settable material such as mortar or concrete and an upper column section 13 of compacted ballast. Between the two is a transition section 14, which is formed by the fact that gravel is shaken into the not yet set material of the column 12. On the column heads 15 is a single foundation or strip foundation 16, which protrudes from the processed planum 17. The planum 17 is covered with a foundation plate 18, which fills the spaces between individual foundations 16. The individual foundation 16 forms a vault structure with two columns 11 or with two rows of columns.

In FIG. 2 a vertical bottom section is shown in which in turn two vertical columns 11 are cut. These also each consist of a hardened lower column section 12 of abbindbarem material, an upper column section 13 of compacted ballast and a transition section 14, which is formed by gravel is shaken into the not yet set material of the column 12. In this case, the subgrade 17, on which a continuous foundation plate 18 rests, is formed by an equalization layer 19, which fills up the spaces between the column heads 15. In the area of the columns 11, the foundation plate 18 rests directly on the column heads 15. In this case, a vault is formed by two pillars 11 or two rows of columns and the compensation layer 19.

The same graphic representations for the material do not necessarily correspond to the same materials used in the two FIGS. 1 and 2 ,

In FIG. 3 in representation a) the production phase 1 for the production of a lower column section, in illustration b) the production phase 2 for the production of an upper column section and in figure c) a schematic diagram of a tool for the first production phase are shown. In the first phase there are three steps (1 to 3), in the second phase two steps (4, 5) are distinguished.

In the first step, it is shown how a working scaffold 22 for a screwdriver 23 is provided on a supporting bead 21. The upper end of the auger 23 is connected via a hose 24 to a concrete pump 25. If necessary, concrete or fresh mortar from a vehicle 26 is filled in the concrete pump.

In the second step it is shown how the drilling tool 23 under pure displacement, i. is screwed into the ground waiving lifting a core or ejecting an annulus.

In the third step, it is shown how the drilling tool 23 is pulled while flowing out of the concrete or mortar, wherein substantially no soil is to be excavated further. The concrete or mortar flows substantially without pressure from the interior of the drilling tool 23 in the resulting by displacement borehole 27 a.

In illustration b) is shown in the fourth step, as the tool has been changed on the support crawler 21, wherein now on the working scaffold 22, a known deep vibrator 28 is attached to a feed hopper 29. The deep vibrator is already shaken into the area of the lower column section. By a vehicle 30 ballast is filled into the hopper 29.

In the fifth step, it is shown how the deep vibrator 28 has been pulled, whereby now a lower pillar portion 12 of set material and an upper pillar portion 13 of compacted ballast have been formed.

In illustration c), the lower end of a drilling tool 23 with a screw tube 32 is shown, on which symbolically an externally seated screw 31 for drilling can be seen.

FIG. 4 in representation a) the production phase 1 for the production of a lower column section, in illustration b) the production phase 2 for the production of an upper column section and in figure c) a schematic diagram of a tool for the first production phase are shown. In the first phase are three steps (1 to 3), in the second phase two steps (4, 5).

In the first step, it is shown how a working scaffold 22 for a lowering tube 33 and a topping vibrator 35 is provided on a supporting bead 21. The upper end of the Senkrohres 33 is connected via a hose 24 with a concrete pump 25. If necessary, concrete or fresh mortar from a vehicle 26 is filled in the concrete pump.

In the second step, it is shown how the countersink tube 33 under pure displacement, i. shaking without lifting a core or ejecting an annulus into the ground.

In the third step, it is shown how the lowering tube 33 is pulled while flowing out of the concrete or mortar, wherein substantially no soil is to be excavated further. The concrete or mortar flows substantially without pressure from the interior of the Senkrohres in the resulting by displacement borehole 27 a.

In illustration b) is shown in the fourth step, as the tool has been changed on the support crawler 21, wherein now on the working scaffold 22, a known deep vibrator 28 is attached to a feed hopper 29. The deep vibrator is already shaken into the area of the lower column section. By a vehicle 30 ballast is filled into the hopper 29.

In the fifth step, it is shown how the deep vibrator 28 has been pulled, whereby now a lower pillar portion 12 of set material and an upper pillar portion 13 of compacted ballast have been formed.

In illustration c), the lowering tube 33 is shown, on which a feed hopper 34 and the Aufsatzrüttler 35 can be seen. Furthermore, a controllable flap 36 is shown at the lower end of the lowering tube 33. Instead of the controllable flap, a lid can also be used. Between the Aufsatzrüttler 35 and the hopper 34 is a coupling 37th

LIST OF REFERENCE NUMBERS

11

pillar

12

lower column section

13

upper column section

14

Coverage section

15

column head

16

Single, strip foundation

17

Planum

18

foundation plate

19

leveling layer

20 21

supporting bead

22

work scaffolding

23

drilling

24

tube

25

concrete pump

26

Fresh concrete vehicle

27

well

28

deep vibrator

29

hopper

30

loader vehicle

31

snail's pace

32

check pipe

33

down tube

34

hopper

35

Vibratory

36

flap

37

clutch

Claims (11)

1. A method of foundation ground improvement by introducing piles (11) into the soil, which piles (11) are distributed in the form of a grid over the surface and which each comprise a lower bound pile portion (12) out of a bindable material such as mortar or concrete and an upper compacted pile portion (13) comprising an non-cohesive material such as crushed stones, wherein, for producing the lower pile portion (12) a hollow tool is sunk thereby displacing the soil and, while the hollow tool is being lifted, the bindable material is moved out of same and introduced into the borehole (27),
   characterised in
   that individual or strip foundations (16) or a foundation plate (18) are built up directly on to the heads (15) of the piles (11) .
2. A method according to claim 1,
   characterised in
   that, while the hollow tool is being lifted, the bindable material flows out in an uncompacted condition.
3. A method according to any one of claims 1 or 2,
   characterised in
   that, for producing the lower pile portion, a rotating drilling tool (23) with a surface load is being used.
4. A method according to any one of claims 1 or 2,
   characterised in
   that, for producing the lower pile portion, a vertical pipe (33) with a vibratory hammer (35) is being used.
5. A method according to any one of claims 1 to 4,
   characterised in
   that, for producing the upper pipe portion (13), a depth vibrator (28) is vibrated into the open borehole (27) and, while the depth vibrator (28) is being lifted, the non-cohesive material is moved out of same and introduced into the borehole (27).
6. A method according to claim 5,
   characterised in
   that, for producing a transition region (14) between the two pile portions (12, 13), the depth vibrator (28) is vibrated into the lower pile portion (12) prior to the bindable material having set, in particular by approximately 0.5 m.
7. A method according to any one of claims 1 to 6,
   characterised in
   that, by means of the hollow tool, a borehole (27) with approximately 200 to 600 mm diameter is produced by displacement only.
8. A method according to any one claims 1 to 7,
   characterised in
   that the borehole (27) is produced down to a depth of approximately 20 m.
9. A method according to any one of claims 1 to 8,
   characterised in
   that a compacted compensating layer (19) is produced between the heads (15) of the piles (11), on which the foundation plate (18) is produced.
10. A method according to claim 9,
    characterised in
    that the compensating layer (19), on which subsequently there is produced the foundation plate (18), is produced prior to the production of the piles (11) whose heads (15) reach as far as and into the compensating layer (19).
11. A method according to claim 1 to 10,
    characterised in
    that a grid with a grid dimension of approximately 4 m is used for arranging the piles (11).

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