EP1995407A2 - Method for consolidating and/or sealing loose geological formations in the process of geotechnical construction - Google Patents

Abstract

The method involves making a tunnel wall and/or a slotted wall, for example, essentially by feeding a supporting medium consisting of a clay mineral suspension and a pore filler to a working region (6) involves adding a swellable soluble clay mineral granulate to the clay mineral suspension as a pore filler. An independent claim is also included for a supporting medium, especially for stabilization and/or sealing of loose geological formations.

Description

The invention relates to a method for solidifying or stabilizing and / or sealing looser geological formations in the course of geotechnical construction measures, in particular for the production of a tunnel and / or diaphragm wall, preferably for use in liquid-supported machinellen tunneling and trench wall method, which essentially consists of a clay mineral suspension and a pore filler existing support medium is supplied to a work area or a respective slot.

Such methods are well known in the art and are used, for example, in automated liquid-assisted tunneling, both for vertical and horizontal wells. In addition, such methods are used in the introduction of slot walls, as used for example in the production of sealing wall masses. Reference is made in this context to the DE 198 43 092 C2 which deals with a sealant mass producible by placing and milling a particular bentonite in a microporous state and then mixed with cement in a one-shot process or predispersed in a two-step process with water and then stirring said cement or Portland cement ..

In addition one knows by the EP 0 696 558 A2 a very fine cement binder mixture which is used for producing a cement suspension for filling and / or pressing, for example, pore spaces in loose rocks. - A generic method describes the WO 87/05925 A1 , Here comes a plastic material as pore filler used.

The dissertation of Dr. Anja Heinz "Modified bentonite suspensions for geotechnical construction methods in soils of high permeability" presented at the Institute of Geotechnical Engineering at ETH Zurich in 2006 , Because at this point again different pore fillers are examined and addressed, such as sand, vermiculite, mica, sawdust or cement. Also paper undergoes a treatment and appreciation as a pore filler. In addition, pure bentonite suspensions are detected experimentally.

The state of the art can not completely satisfy. Thus, when using the described geotechnical construction measures, that is, in particular in the case of liquid-supported mechanical tunneling, in the slot wall technology and possibly the drilling technique in loose geological formations or coarse-grained soils, the clay mineral suspension is subject to high losses as a result of its high water permeability. This is economically hardly feasible, because, for example, when tunneling constantly clay mineral suspension must be supplied. Incidentally, the introduction of the clay mineral suspension in the soil causes the supporting effect may no longer be sufficient, so that there are security problems.

In order to minimize the penetration of the suspension, their rheological properties are of great relevance, in other words their flow behavior. The penetration depth of the clay mineral suspension essentially depends on the pore space, the pore size of the geological formation and on the yield point of the clay mineral suspension. If the corresponding formation is very permeable, it either has large pores or a high number of pores, or both come together.

In the case of small pores, the penetration can be limited by the yield strength of the suspension; with large pores, this is no longer technically possible. Because For this, the suspension would have to be pasty, and consequently can no longer be pumped off, reprocessed and recirculated, as is generally the case in tunnel boring machines (cf. DE 198 59 821 A1 ). For this reason, one has worked in the prior art with various pore fillers, wherein in practice pore fillers such as sand, vermiculite, sawdust or shredded paper are added to the clay mineral suspension.

Here, however, there is the problem that the pore fillers in the reprocessing of the support medium, so the mixture of the clay mineral suspension and the pore filler, must be discharged together with any soil components. This can be done by, for example, screening and / or filtering. In this regeneration of the pore filler is lost and must be transported together with the soil components or the excavated soil and disposed of.

This not only leads to increased costs for removal and disposal, but also requires a constant supply of consuming pore filler. Quite apart from regeneration plants can be clogged by, for example, sawdust or shredded paper, so are possibly impaired in their function. Especially with large diameter tunneling, the latter aspect can lead to significant problems because the performance of an associated regeneration plant limits propulsion performance. - Here the invention aims to provide a total remedy.

The invention is based on the technical problem of further developing such a method so that the reliability increases, the regeneration of the support medium is facilitated and overall the costs are reduced.

To solve this technical problem, the invention proposes in a generic method for solidification or stabilization and / or sealing looser geological formations in the course of geotechnical construction measures that the clay mineral suspension is added to a swellable soluble clay mineral granules as Porenfüllstoff.

The invention thus relies on a special pore filler, namely a swellable clay mineral granules, which is also soluble in the associated suspension liquid. That is, in the suspension liquid are not only the very fine solid clay mineral particles forming the suspension, but also the clay mineral granules. All three of the aforementioned ingredients (suspension liquid, fine clay mineral powder or fine solid clay mineral particles and clay mineral granules) form a total of the support medium which is supplied to the work area. This work area is usually, and not limited to, the so-called working face in liquid mechanical tunneling.

Since the clay mineral granules are soluble in the suspension liquid, measures must be taken that the clay mineral granules in the work area nevertheless fulfills its primary function, namely to clog pores in the loose or stabilizing loose geological formation. This is preferably achieved by the invention in that the clay mineral granules are added to the clay mineral suspension at a predetermined (short) time before reaching the working area. In this case, the time in question is so dimensioned that the clay mineral granules of the suspension liquid has not or almost not been dissolved. As a consequence of this, the clay mineral granules are available in the working area with the grain size predetermined at the time of admixture with the clay mineral suspension.

In fact, the invention recommends at this point a grain of Tonmineralgranulates with particle sizes or diameters of more than half a millimeter up to about 20 millimeters. Usually, a particle size range between 1 millimeter and 16 millimeters is covered, depending on how the loose geological formation to be consolidated or sealed is designed or depending on the observed or measured pore size in the working area.

The pore size of the relevant geological formation is either known or can be determined prior to introduction of the support medium. Depending on the pore size of the loose geological formation to be consolidated or sealed, the clay mineral granules are then selected with regard to their grain size. The grain size of the clay mineral granules is usually adjusted so that at least 70%, usually more than 80% and preferably at least 90% of the pores of the loose geological formation of the clay mineral granules or its grains are clogged. At the same time it is important not to choose the particle size of the clay mineral granules too large, so as not to hinder the reprocessing. Here, 20 millimeters in diameter have proven to be the upper limit for the grain size.

In fact, the support medium is in fact preferably reprocessed by discharging any soil constituents and / or individual grains of the clay mineral granules which have not or not completely dissolved in the course of the processing of the support medium. At the same time, the reprocessing provides that suspension medium and / or the clay mineral granules and / or the clay mineral are added as a clay mineral powder as needed to the support medium. The invention is therefore based on the fact that the clay mineral granules dissolve advantageously during its processing in the work area and / or the return transport wholly or partially in the clay mineral suspension, thus no problems in the reprocessing or in a regeneration plant leads. That is, any existing sieves there can not clog, overflow and it does not come to foam.

Incidentally, the grain size can be varied by changing the timing of adding the clay mineral granules to the clay mineral suspension. If this time is well before the work area is reached, it is to be expected that the original grain size has been changed (reduced) by, for example, swelling or dissolving. On the other hand, if the addition is made shortly before reaching the working range, practically no change in the grain size is observed. Depending on the solubility of Tonmineralgranualtes in the suspension liquid, the time of addition of Tonmineralgranulates the clay mineral suspension can be changed to that undergoes a predictable reduction in diameter during transport to the work area, the grain size.

It is possible that the clay mineral granules after its processing and the return transport for the reprocessing of the support medium has a grain size which is in the range of fine clay mineral particles of the clay mineral suspension. As a result, for example, start a liquid-based tunneling with a conventional amount of fresh clay mineral suspension and can be maintained only by adding clay granules and suspension liquid. That is, the addition of the clay mineral granules and the suspension liquid compensates for losses incurred, while maintaining the rheologically necessary properties at the same time.

This advantageously contributes to the fact that both the clay mineral suspension and the clay mineral granules can be produced from a respective matching clay mineral. As a result, the rheological properties on the one hand the clay mineral suspension and on the other hand, the mixture of the Adjust the suspension liquid and the clay mineral granules to each other. If consistent clay minerals are used, the rheological properties are virtually identical. - Of course, the invention does not exclude that the support medium to optimize its stability and the rheological properties of other mineral or organic additives are added.

A supporting medium is always provided within the scope of the invention, which is preferably used for producing a tunnel and / or trench wall or in the course of a mechanical tunneling or in the slot wall technique and in the working area or slot the existing pores in the geological formation or Clogged reliably in a soil. For this purpose, the pore size of the soil is first determined and, depending thereon, the grain size of the clay mineral granules is selected and added to the clay mineral suspension. In addition, the time of adding the clay mineral granules to the clay mineral suspension can be specified, if this time can be changed.

Unused and dissolved soil granules are transported away together with the clay mineral suspension and any soil components or a Bodenaushub for regeneration of the work area. In this case, the clay mineral granules dissolves completely or almost completely by the mechanical stress in the work area and during transport and is not separated out of the support medium in the subsequent regeneration of the mixture of the support medium and the soil components or the excavated soil.

Because the clay mineral granules dissolved in the suspension liquid have approximately the same rheological properties as the clay mineral suspension, the clay mineral granules dissolved in the suspension liquid ensure that the already used and reprocessed clay mineral suspension is supported in its stability and its reological quality. Thus, the support medium is not overly thickened by any enrichment with the clay mineral granules and impaired in its flowability, the recycled support medium can be added depending on its viscosity additionally suspension liquid for dilution and impaired in its flowability, the re-prepared support medium depending on his Viscosity in addition to be added suspension liquid for dilution. This suspension liquid is usually water.

Depending on the addition amount of the clay mineral granules to the clay mineral suspension to form the support medium, the addition of fresh clay mineral suspension may be partially or completely omitted. Any problems occurring in the prior art when regenerating the supporting medium in connection with the soil constituents or the soil excavation do not occur. Here are the main benefits.

Fig. 1

eine Tunnelvortriebsmaschine schematisch und

Fig. 2

den Tunnelvortrieb im Bereich seiner Ortsbrust.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment; show it:

Fig. 1

a tunnel boring machine schematically and

Fig. 2

tunneling in the area of its face.

In the Fig. 1 is a tunnel boring machine shown in its basic structure, with the help of a first slot 1 according to the Fig. 2 is generated along the planned tunnel circumference. For this purpose, the tunnel boring machine has a Schlitzgrabvorrichtung 2, which generates the aforementioned slot 1 and produces a support layer 3. In the embodiment the Schlitzgrabvorrichtung 2 is formed mehrgliedrig to adapt to different radii.

In the Fig. 1 can be seen on the front of a tool 4 for the removal of material, which may be one or more cutting wheels. These cutting wheels rotate about an axis A and solve the lying before them rock or soil out of the composite.

Via a supply line 5, a support medium is supplied to in the in Fig. 2 shown working area 6 and the working face 6 to produce the support layer 3. According to the invention, the support medium is a mixture of a clay mineral suspension and a pore filler in which a swellable, soluble clay mineral granulate is used. The support medium is pumped via several openings on the tool 4 and the associated cutting wheels directly into or to the working face 6.

The supply line 5 opens into a chamber 7, in which the support medium with dissolved out material, in this case loose soil or rock, mixed. Via a discharge line 8, this mixture is then removed from the support medium and any soil components and fed to a merely indicated regeneration plant 9. To the chamber 7, a removal device 10 is still connected, by means of which the material removed from the tool 4 can be removed from the area of the tool 4. Overall, however, the removal device 10 represents only one option.

In the rear part of the chamber 7, an air chamber may be provided. In this case, an air bubble forms in the chamber 7, which is kept at a certain overpressure. This overpressure propagates via the support medium located in the chamber 7 to the geological formation to be processed.

With the help of the regeneration system 9, the mixture of the support medium and the soil components is reprocessed in such a way that the soil components are usually sieved out and the remaining support medium is conveyed again via the supply line 5 into the chamber 7.

Advantageously, the support medium has as pore filler on a swellable and soluble clay mineral granules, which has a grain size of more than 0.5 millimeters. So that the mixture of the soil components and the support medium remains unchanged flowable and can still be supplied to the regeneration plant 9, the grain size of the clay mineral granules is limited to 20 millimeters usually. The clay mineral granules are metered into the supply line 5 just before the chamber 7 at a time T and taken by the guided here Tonmineralsuspension in the chamber 7.

In this case, the time T of this admixture or addition of the clay mineral granules to the clay mineral suspension is fixed or predetermined and corresponds to a time until the support medium in question has reached the working area or the working face 6. This period of time or the time T of admixture of the clay mineral granules is so dimensioned that the clay mineral granules in the suspension liquid has not been or almost not dissolved. Basically, the time T can also vary. Then, the individual grains of the clay mineral granules can be selectively dissolved to provide a certain desired grain size spectrum available and / or replace part of the clay mineral suspension by the loosened clay mineral granules or add to the clay mineral suspension to achieve certain rheological properties.

If the clay mineral granules in the suspension liquid has not been or almost not dissolved, it is ensured that the clay mineral granules in Achieving the working area or the working face 6 has virtually the same grain as at the time T of admixture to the clay mineral suspension in the supply line 5. The grain size of the clay mineral granules is determined depending on the pore size of the loose geological formation to be solidified or sealed. For example, the design may be such that the grains of the clay mineral granules are formed greater than 90% of the pores of the geological formation in question. This can ensure that the vast majority of the pores in question are clogged by the clay mineral granules in the support medium. Of course, an upper limit of 80% or even 70% of the pore size can be thought of and is encompassed by the invention.

At the same time, the maximum grain size to be processed, which is ultimately determined by the regeneration system 9, must be taken into account. Because if one or more of the clay mineral granules are not or not completely dissolved in the working area 6 or during their return through the discharge line 8 to the regeneration system 9, it should nevertheless be ensured that any screens or filters in the regeneration system 9 are not blocked. This is usually achieved when the grain size of the clay mineral granules does not exceed 20 millimeters, and preferably 16 millimeters.

Incidentally, the rheology of the support medium, that is, its flow behavior, particularly advantageous in the case influenced that the clay mineral suspension and the clay mineral granules each have a matching clay mineral or have been prepared from a matching clay mineral or a respective matching clay mineral mixture. As a clay mineral, the invention recommends recourse to a three-layer mineral or the mixture of several three-layer minerals, each with intracrystalline swelling capacity. In particular, smectites and here preferably bentonites are used. These have the desired swelling capability to to solidify and / or seal the loose geological formation and are at the same time soluble in the suspension liquid, preferably water.

The particularly advantageously used bentonites for the clay mineral suspension and / or the pore filler is preferably a soda-activated calcium bentonite. Because of its agregated structure, such a bentonite forms a high yield point even at low concentrations in suspensions. At the same time, its viscosity is lower and the tiksotropic behavior more favorable than with natural sodium bentonite. Consequently, the described soda-activated calcium bentonite is particularly suitable for the described application.

In any case, a dense filter cake forms rapidly and prevents further penetration of the suspension. In this respect, the high yield strength observed with soda-activated calcium bentonite also has a positive effect because it limits the penetration of the suspension into the geological formation to be consolidated or stabilized, after which the filter cake has formed.

Finally, it should be emphasized that the time T of admixture of the clay mineral granules to the clay mineral suspension can be varied. This is achieved by the invention, for example, in that 5 different openings for introducing the Tonmineralgranulates be provided in the longitudinal direction of the supply line. The addition of suspension liquid or water can also be changed in order to dissolve or dissolve the clay mineral granules. With the aid of existing in the lines 5, 8 and / or the chamber 7 and / or in the regeneration system 9 sensors, the various parameters such as grain size of Tonmineralgranulates, fluidity of Tonmineralsuspension, content of suspension liquid, etc. can be detected and fed to a control unit for processing , The control unit then regulates the supply of clay mineral granules, its grain size, the time T of admixture, the addition of suspension liquid, etc.

Claims (10)

Method for solidifying and / or sealing looser geological formations in the course of geotechnical construction measures, in particular for producing a tunnel wall and / or diaphragm wall, according to which a support medium consisting essentially of a clay mineral suspension and a pore filler is fed to a working area (6), characterized that the Tonmineralsuspension a swellable soluble Tonmineralgranulat is added as Porenfüllstoff. A method according to claim 1, characterized in that the clay mineral granules at a predetermined time (T) before reaching the working area (6) of the clay mineral suspension is added, the time (T) is such that the clay mineral granules upon reaching the working area (6) from a suspension liquid of the clay mineral suspension has not or almost not been dissolved. A method according to claim 1 or 2, characterized in that the grain size of the clay mineral granules is adjusted in accordance with measured pore sizes in the working area (6). Method according to one of claims 1 to 3, characterized in that the time (T) of admixture of the clay mineral granules is varied to the clay mineral suspension in order to specifically dissolve the clay mineral granules. Method according to one of claims 1 to 4, characterized in that the clay mineral granules dissolves during its processing in the working area (6) and / or the return transport wholly or partly in the clay mineral suspension. Method according to one of claims 1 to 5, characterized in that the support medium is recycled by discharging any soil components and the suspension liquid and / or the clay mineral granules and / or the clay mineral suspension are added if necessary. Supporting medium, in particular for use in the solidification and / or sealing of loose geological formations in the course of geotechnical construction measures, preferably for use in tunnel and / or diaphragm wall construction, consisting essentially of a clay mineral suspension and a pore filler, characterized in that a swellable as a pore filler soluble clay mineral granules is used. Supporting medium according to claim 7, characterized in that the clay mineral granules have a particle size of more than 0.5 millimeters up to about 20 millimeters, in particular between 1 millimeter and 16 millimeters. Supporting medium according to claim 7 or 8, characterized in that the clay mineral suspension and the clay mineral granules are produced from a matching clay mineral. Supporting medium according to one of claims 7 to 9, characterized in that as a clay mineral for the clay mineral suspension and / or the clay mineral granules, a three-layer mineral with intracrystalline swelling capacity, in particular a smectite, preferably bentonite, is used.

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