GB2398812A

GB2398812A - Method and device for ground stabilization

Info

Publication number: GB2398812A
Application number: GB0408472A
Authority: GB
Inventors: Hans-Joachim Bayer
Original assignee: Tracto Technik GmbH and Co KG
Current assignee: Tracto Technik GmbH and Co KG
Priority date: 2001-10-12
Filing date: 2002-10-14
Publication date: 2004-09-01
Anticipated expiration: 2022-10-14
Also published as: WO2003033825A1; DE10150278A1; GB0408472D0; DE10150278B4; GB2398812B

Abstract

The invention concerns a method for ground stabilization which consists in incorporating, by mixing, a consolidating agent. The invention is characterized in that it consists in drilling a pilot borehole in the ground to be consolidated with a tool arranged at the end of a tie rod provided with a forward rotational driving system, replacing the tool with a mixing member introducing the consolidating agent. withdrawing the mixing member through the pilot borehole. The mixing member has a larger diameter than the pilot borehole and incorporates, by mixing, the consolidating agent in the underground surrounding the pilot borehole.

Description

"Method and device for ground stabilization" The invention relates to a

method and a device using which a consolidating agent used for ground stabilization can be mixed into the soil, for example at a building site.

Methods for the in-situ consolidation of layers of soil close to the surface are known; they are used, for example, to increase the loadbearing capacity or to bind or render inert pollutants in the soil, so that no further hazard can originate from them. For this purpose, these methods make use of various means. In addition to mechanical consolidation, for example by means of compaction and vibration, the introduction of a binding agent for improving the cohesion of the soil has proven to be particularly useful. For example, the load-bearing capacity of a non-cohesive soil can be improved permanently by means of the introduction of a

cement/water mixture. The introduction of the

consolidating material at greater soil depths can be done with a screw conveyor, which is guided through a funnel-like storage container and initially creates a bore in the course of displacing soil. As soon as the final depth of the bore has been reached, the screw conveyor is pulled back while rotating, the stabilizing or consolidating agent in the storage container being conveyed downwards into the bore and permitting a braced column to be produced in the soil, depending on the pulling speed and delivery capacity. Depending on the soil composition, a large number of columns are required, whose spacing is 0.2 to 1.5 m.

The method is very time-consuming and costly; it is therefore not suitable for large-area ground stabilization, in particular when the composition of the soil requires a small column spacing. In addition, the column diameter can never be larger than the diameter of the screw conveyor used as a drilling tool. - 2

This disadvantage also results in the case of a method in which a powdery or granular consolidating agent, for example cement or lime, is introduced pneumatically into a vertical bore and is mixed with the soil by a mixing tool being moved towards the surface of the ground with the aid of a drilling linkage. Mixing blades of the tool ensure thorough mixing of the ground and the consolidating agent.

The invention is based on the problem of creating an economic alternative for the stabilization of soils with the aid of vertical columns.

The invention achieves this object by means of a method in which first of all a substantially horizontal pilot bore is introduced into the ground to be stabilized and then a mixing element discharging a consolidating agent is moved, for example pulled, through the pilot bore.

The mixing element can be supplied with the consolidating agent in the direction of movement and/or opposite to the direction of movement, for example via a hose or a linkage.

Particularly good mixing of the ground surrounding the pilot bore and the consolidating agent results if the mixing element moves, for sample rotates, has a larger or considerably larger diameter than the pilot bore and/or rotates during its forward movement.

In order to loosen the ground and/or for the purpose of better mixing, cutting elements can be arranged in front of or on the mixing element in the forward drive direction.

The pilot bore is preferably produced with the aid of a boring tool which is arranged on a driven linkage and which is replaced by a mixing element following the finishing of the pilot bore. The mixing element is then pulled through the pilot bore with the aid of the linkage and, in the process, mixes the consolidating agent into the ground. The diameter of the mixing element in this case determines the region of the ground surrounding the pilot bore which is mixed with the consolidating agent.

The consolidating agent can be introduced into the ground dry, for example pneumatically, or else injected in.

The mixing element can comprise a nozzle ring joined to a connecting piece via struts or a hub with protruding blades. The blades can be provided with slot-like and/or circular outlet openings for the consolidating agent; they can be arranged in such a way that the overall result is a star-like mixing element. However, the mixing element can also substantially comprise fins, for example wedge-like fins, arranged at angles to one another or else nozzle arms connected to one another via a distributor.

The mixing element is preferably arranged on a linkage which is connected to a rotary drive and can consist of two concentric pipes arranged at a distance from each other, and then offers the possibility of delivering two media separately from each other through the inner pipe and the annular space between the two pipes.

The nozzles or outlet openings for the consolidating agent are preferably funnel-like or, in cross section, wedge-like, widening outwards, in order to avoid blockages resulting from the, for example powdery, consolidating agent.

The mixing element can also have individual eccentricities for better mixing of the ground and the consolidating agent, but overall should be composed in such a way that the result is a substantially - 4 rectilinear movement through the soil to be consolidated. In order to ensure this, the linkage should be sufficiently rigid in order at the same time also to avoid blockages at linkage bends.

The invention permits ground stabilization to be carried out without detriment to the surface of the ground, for example under buildings, roads and railway embankments. This can also be done in a plurality of layers above one another and/or beside one another.

The invention will be explained in more detail in the following text using exemplary embodiments illustrated in the drawing, in which: Fig. 1 shows a device for mixing in consolidating agents with consolidating agent supply on one side, Fig. 2 shows the device according to Fig. 1 but with consolidating agent supply on two sides, Fig. 3 shows a cage-like mixing element, Fig. 4 shows a star-like mixing element, Fig. 5 shows a mixing element with radial fins and Fig. 6 shows a mixing element with a plurality of nozzle arms.

The device for ground stabilization substantially comprises a mount 3 which is provided with a chassis 1, can be pivoted by a lifting cylinder 2 and has a rotary drive 4 arranged on a carriage for a linkage 5 comprising individual pipe sections. The linkage 5 is supplied via a line 9 with a fluid consolidating agent from a storage container or else mixer 8 arranged on a trailer 6 belonging to a plant vehicle 7.

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At the end of the linkage 5 there is a mixing element 10, which is pulled through a pilot bore 11 by the rotating linkage 5. The mixing element 10 has a larger diameter than the pilot bore 11 and therefore mixes the consolidating agent supplied via the linkage 5 into the ground surrounding the pilot bore. In this way, a strand 12 of consolidated material is produced in the direction of movement behind the mixing element.

The pilot bore 11 can be produced by tried and tested methods with the aid of a tool arranged at the free end of the linkage 5. As soon as the tool has reached the surface of the ground at the exit point 13, it is replaced by a mixing element 10 which is then pulled back in the direction opposite to the boring direction with the aid of the linkage 5 as far as the starting position 14 while rotating. Alternatively or else additionally, as illustrated in Fig. 2, the mixing element can be supplied with consolidating agent via a consolidating agent line 15 from a mixer 16 with a silo 17.

The mixing element can have a very variable composition; it is critical that thorough mixing of the ground and of the consolidating agent is ensured and that it follows as accurately as possible the line predefined by the pilot bore 11 and the linkage 5.

In detail, the mixing element can comprise a nozzle ring 18 in the manner of a cage with outlet openings 19 for the consolidating agent. The nozzle ring 18 is joined via hollow struts 20 to a connecting piece 21 which is formed as a distributor for the consolidating agent and, for example, is screwed to the linkage 5 (Fig. 3).

In the exemplary embodiment of Fig. 4, a hub 22 serving as distributor is provided with radially protruding blades 23 and screwed to the linkage 5. The edges of the blades 23 pointing rearwards, as based on the direction of movement, have funnel-like outlet openings 24 for the consolidating agent. The outlet openings can also be slot-like, but should widen outwards as far as possible in order to avoid a blockage.

As can be seen from Fig. 5, the blades can also be formed as wedge-like fins 25 and, at their edges 26 pointing rearwards, can be provided with teeth 27 loosening the ground.

Finally, individual nozzle arms 28 can also protrude from the hub 22, of which the ends with outlet openings 24 are used for the consolidating agent. A mixing element of this type acts like a stirrer in the ground.

The ground stabilization does not need to start from the surface of the ground, as illustrated in Figs 1 and 2, and then follow a curve-like line. It is also possible to create a straight consolidating strand, for example between a starting excavation and a target excavation.

Claims

Patent claims: Method for ground stabilization by mixing in a

consolidating agent, characterized in that first of all a pilot bore (11) is introduced into the soil and a mixing element (10) discharging a consolidating agent is then moved through the pilot bore.
2. Method according to Claim 1, characterized in that the mixing element (10) is supplied with consolidating agent in the direction opposite to its direction of movement.
3. Method according to Claim 1 or 2, characterized in that the mixing element (10) is supplied with consolidating agent in the pulling direction.
4. Method according to one of Claims 1 to 3, characterized in that the mixing element (10) rotates during the mixing.
5. Method according to one of Claims 1 to 4, characterized in that the pilot bore (11) is produced with the aid of a boring tool which is arranged on a driven linkage (5), the boring tool is then replaced by the mixing element (10), the mixing element is pulled through the pilot bore with the aid of the linkage and, in the process, a consolidating agent is mixed into the ground surrounding the pilot bore.
6. Method according to one of Claims 1 to 5, characterized in that the consolidating agent is injected into the ground.
7. Device for ground stabilization by mixing in a consolidating agent, characterized by a mixing element (10) arranged on a pulling means (5). 8
8. Device according to Claim 7, characterized by a nozzle ring (18) joined to a connecting piece (21) by struts (20).
9. Device according to Claim 7, characterized by a hub (22) with radially projecting blades (23, 25).
10. Device according to Claim 7, characterized by nozzle arms (28) connected to one another via a distributor (22).
11. Device according to one of Claims 7 to 10, characterized by funnellike outlet openings (24).
12. Device according to one of Claims 7 to 11, characterized by slot-like outlet openings (24).
13. Device according to one of Claims 7 to 12, characterized in that the mixing element (10) is arranged on a linkage (5) connected to a rotary drive (4).
14. Device according to Claim 13, characterized by a linkage (5) comprising two pipes arranged at a distance from each other.
15. Device according to one of Claims 7 to 14, characterized by additional cutting blades in front of or on the mixing element.