The method comprises a first step of forming borings into the soil under protection of gap-slush and developing narrow slots therebetween by blowing the cutting edge secured to the bottom of foil boards, and a second step of connecting the connecting elements of foil boards recessed into the borings by means of compensating joint-pins and repeating the latter operation up to the last boring. In a preferred embodiment of the invention, might be set an armouring into the borings, then injected concrete in the place of the gap-slush.

The present invention enables to effectively build a cutoff, without the need of trenching, such cutoff will have a creep-line increasing behaviour depending on its distance to the confining bed, and also having any load-bearing characteristic, because of its facet-like arrangement.

Background Art The presently known methods of cutoff building have been appeared and started to become diffused in the early fifties-in the mid-sixties in Hungary-, since their application for basement, sheeting and bracing of a building pit, building of underground structures, as well as for water seal objects is more advantageous than the different conventional technologies.

The body of the method of the present invention involves making a gap or cutting -under protection of mud or gap-slush protecting the stability of the wall-having a vertically arranged wall going ahead downwardly from the surface, then constructing the structure getting out the gap-slush simultaneously or posteriorly from the gap.

The cutoff building technology is determined by the behaviour of the applied machines. Every machine being able to build a continuous, load-bearing and/or water seal wall by building-in of suitable materials in a depth beneath its moving plane, will be applicable to build a cutoff.

Altogether, the cutting action-but always in case of large cuttings-involves two basic steps: excavating the soil and filling the gap.

It is possible to draw a distinction between the applicable technologies according to the method of how the soil structure being in the place of the material of the wall volume becomes got out (carried away, respectively). Accordingly, two primary method is known: The ditcher applying technology has two essential characteristic, namely -the soil mellowed by the cutting tool might be excavated from the gap to the surface by the vertical movement of the tool of the ditcher controlled from the ditcher, -during the excavation, the slush filling the gap might be mixed due only to the upward and downward movements of the tool.

Applying the drilling methods, only mellowing and braying of the soil are made by the cutting tool (borer, cutter, cutterhead).

The mellowed solid material admixed to the slush being in circulation is got out to the surface in form of slurry. (After backing and cleaning of the slurry the slush is fed back into the gap) The slush acts in this technology as an agent enhancing the stability of the gap and also excavating the solid material. This method for build a cutoff had

been developed from the so-called'left-flushing' (back-flushing) drilling technology and the appearance of bentonite suspensions having tixothrope characteristics-as a drilling slush or cutting sludge-had had a role of vital concernment.

The aforementioned methods working with soil excavation are applicable to form wide gaps, but a narrower cutoff can be formed by compaction to the side wall of the gap, ergo without excavation of the soil. Among this methods there is the ETF method and its developed variants having a practical relevance.

This method-in substance-comprises of a first step of longitudinally attaching injecting tubes to a high-webbed double-tee beam (or to a cutting tool having any kind of other profile), then hammering it down by machine to a depth according to the cutoff being to build, and a further second step of grouting contemporaneously of the beginning of cutter-flitting an afterhardening bonding material passing through the tube (tubes) into the gap, and after the solidification of the bonding material a cutoff block will be formed. Patent description HU P 94 03 231 relates to a preferred implementing of the injection and a composition of injected material (s).

The continuous cutoff consists of cutoff blocks being formed one after another, the continuity of which is established with a so called'cutting back'action. Applying two cutting tool at the same time the second one remains in the soil as long as the gap of the first one becomes fully injected. This technology can be advantageously achieved also by a cutting tool disclosed in the granted patent HU 167 865.

Disadvantages of this known method are the laboursome and slow building process, and that fact, that the complete cutoff (membrane wall) has a diminished water sealing or bleeding decreasing only, not to be loaded and it can be built into a shallow depth only.

Structural embodiment of the cutoff-structures realised in the wide cuttings depends on the scope of the cutoff (whether it should be bleeding decreasing and/or load bearing too).

Some case the slush enabling the stability of the cutoff should act the part of the final structure. Such a cutoff and gap filling material (cement, water, bentonite and retarding agent) are known from the patent description HU 181284.

HU 169 315 discloses a method in which prefabricated wall members are sunk into the gap sustained by thin-liquid slurry, then the gap will be formed between the wall members and the walls of the gap shall be filled with afterhardening binder material injected into the bottom of the cutting.

In the case of concrete walls prepared in wide gaps the continuous cutoff is typically built from sections. Such a method can be known from the patent description HU P 84 4727, this method involves a step of building a concrete wall in any section of the cutting, and a second step of locating a recoverable spacing member between this section and the cutting sustained provisionally by thin-liquid slurry, and the continuous water sealing contact is provided by a resilient, permanently located water-proof strip.

The structure and building method of a boarded-panel type cutoff comprising bearing board and sealing board is known from the patent EP 0 333 639, in which the place of the bearing boards (tubes made from steel) filled and surrounded by concrete, is made by drilling technology.

The cutoff described in the patent US 4.304.507 is able to bear considerable loadings. The building of this cutoff takes place by means of making borings being in predetermined distances from each to another, then steel beam of H shaped profile are located in the borings, and then excavate the place of cutoff boards by means of pressurised water beam.

In the case of greater impermeability (or bleeding decreasing) to obtain, secondary sealing devices are applicable in the tixothrope or afterhardening (hardening) material filling the wide cutting.

The provisional publication DE OS 3436 735 discloses a solution, in which a plane type barrier layer interlaced with connecting elements and embedded into a wide cutting filled with suspension and having barrier element consisting HDPE, is formed.

The patent description EP O 298 283 discloses a method, in which a barrier wall made of glass panels embedded into the slush being in the gap is provided, the inner cavities of connecting links of the wall are filled by the slush.

From the Hungarian patent HU 42 591 89 is known a method, in which the foil sheets provided with connecting links at the edges thereof are sunk into the gap by the force exerted to the bottom part of the foil sheet (to ensure the closure of the connecting members), and thereafter a fusible material should be filled between the foil and the walls of the gap.

In the provisional publication DE OS 34 44 682 an other solution is suggested, in which the wide gap is filled with a hardening sealing compound, then a narrow gap should be formed mechanically or by means of compressed water beam, and the barrier foil is placed therein.

According to a developed solution of the latter disclosed in the patent disclosure DE 38 23 784 borings are provided in the mass filling the wide gap and posts of a slitting cutter device are guided in the borings so forming (feeding supporting liquid contemporaneously) the narrow gaps connecting the borings, then secondary sealing foil interconnected with connecting elements shall be placed into the cuttings.

In this case the scope of forming of the borings is to create a narrow gap being exactly in the longitudinal midline of the wide gap to obtain a perfectly water-proof sealing.

It can be seen from the aforementioned solutions, that each of these known methods require a time consuming and expensive soil excavation.

The methods applicable without excavation of the soil have a serious depth- confinement due to the enormous friction force acting between the cutting tool and the wall of the gap, and the injected cutoff created this way is a lesser water-proof one (and barely loadable).

Disclosure of the Invention It is an object of the present invention to provide a curtain-wall, which could be built almost up to the depth measure of known cutoffs, the cutoff according to the present invention could have a good water-proof characteristic, low production costs and a short production time compared to the known solutions.

We have found that fact, that the trenchless grouting technologies combining with drilling methods are able to sink into the soil the plane type sealing elements and open the narrow gap contemporaneously so that the cutoffs in progress intersect the inner space of the borings filled with slush and already prepared. In this case, the side friction acting to the side walls of the sealing element will be decreased due to the slush flowing from the borings into the opening gap and withal this will afford an opportunity to contact the sealing element in a stress-free and water-proof way and to create a continuous cutoff.

According to this fact, the present invention relates to a method to build a continuous cutoff, in which borings having predetermined distances therebetween and foil boards will be formed in the soil, according to the length of the cutoff and under protection of gap-slush, and a cutting edge protruding over the edges of the foil boards will be secured onto the bottom of the foil boards provided with connecting members well known in itself in the art, and then the foil board will be hammered down into the

soil up to the desired depth by means of beetle-rods driven by adjacent borings and placed onto each two end of the cutting edge of the foil board, and after the hammering down of the following foil board, the edges of the foil boards will be connected in the space of the intermediate boring by means of a compensating joint-pin, and further repeating these operations along the full length of the cutoff.

In a preferred embodiment of the method accordig to the invention, above the surface of the soil, the two beetle-rods working in the same stroke will be rigidly connected each to other and hammered down together.

Advantageously, in the method according to the invention, the foil boards consist of HDPE material.

The compensating joint-pins connecting the foil boards are foil strips advantageously made of the same material, and having connecting members creating a form-fitting pair at their edges connecting to the connecting members of the foil boards.

In a more preferred embodiment of the method according to the invention, an armouring well known in itself in the art will be placed into the borings, and the compensating joint-pins consist of bridles provided with connecting members, and a volume of concrete displacing the gap-slush will be injected into the bottom of the armoured borings.

Advantageously, the applied beetle-rods consist facets and cross-ribs each arranged inside of the two opposite quadrants of the beetle-rod, and having a face formed by ends of the facets converged to the centreline of the beetle-rod.

In a preferred embodiment of the Method according to the invention, the beetle- rod consists a number of sections detachable jointed each to other, and the facets of the beetle-rod consist of hollowed sheets incurvated to arc at their edges.

The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figures 1. a-1. e show the successive main steps of the method according to the invention, Figures 2. a-2. b show an armoured concrete facet and bentonite type embodiment of the created cutoff according to the invention, Figure 3. show schematically the process of building of the object, and Figure 4. shows the theoretical embodiment of the driving post applied to effectuate the method according to the present invention.

Figure 1. a shows the steps of the method according to the invention. The first step consists of forming borings 2,, 22,23,... 2nazi in predetermined distances to the soil 1.

The forming of borings takes place in a known way, under protection of tixothrope slush filling the borings 21,22,23,... 2n+i.

The following step is the trenchless completion of a narrow gap intersecting the inner space of the adjacent borings 2r, 22.

During the method the foil board 4i being in the narrow gap 31 will be placed under protection of slush flowing from the boring 2r, 22 to the narrow gap 3,, and the opening of the cutting 3i also takes place at the same time.

Mention must be made of the need to refill of the slush leaking off during the creation of the cutoff board.

In the Figure 1. b connecting memberss 5a, 5b attached to the edges of the foil board 4i are shown. These connecting members 5a, 5b are equally shaped, bar-like elements, in this case.

Figure 1. c shows the following step of the method of the invention, in which a narrow gap 31 receiving a foil board 4r is provided.

As can be seen in the Figure 1. d, the foil boards 41,42 hammered down into the soil 1 are connected inside of the boring 21 by means of compensating joint-pins 61 and connecting members 7a, 5b thereof. The compensating joint-pins 61 comprises a foil strip having hollowed connecting members 7a, 7b-like the 5a, 5b connecting members -adjacent to its edges.

It does not find any difficulty in driving the compensating joint-pin 61 into the boring 21, because the operations can be easily accomplished in the material having a tixothrope characteristic as well as there is no danger of becoming stuck, since the dimensional deviation arising from the biased boring 2n,... 2nazi or from the untruth of alignment of the edges of the foil boards41... 4n, by means of the compensating joint-pin 61 having greater wideness than the distance of the edges of adequately flexible foil boards 41... 4n, could be easily corrected.

Figure 1. e shows the following step of the method according to the invention, namely the hammering down the successive foil board 41--4n Figure 2. a shows a top view of a section of the complete facet 13 and bentonite type curtain-wall.

Figure 2. b shows a further embodiment of the present invention, in which the facet 13 comprises an armoured concrete member.

In the case according to this embodiment, after completion of narrow gaps <BR> <BR> <BR> <BR> <BR> provided with foil boards 41... 4n, an armouring mounted previously on the surface will be placed into the borings 2n,... 2nazi filled with tixothrope (bentonite) slush. In addition to the longitudinal armourings well known and conventionally used in the art and the transversal bridles 10 connecting the armourings as mentioned previously, contain concrete steel bridles 10 having connecting members 7a', 7b' on its opposite ends, and the bridles 10 attached to the connecting members 5a, 5b being at the edges of each foil

board 41 4n by means of connecting members 7a', 7b', form the compensating joint- pins 61', 62',... 6 (n-i)) <'.

The insertion of armouring followed by filling concrete into the borings 21, 22,23,... 2n+1 by means of injection displacing the slush, can be executable in the tixothrope material without any difficulty.

The advantage of the solution is that, that this operation (armouring and concreting) shall be executable, after completion of the cutoff, in a moment arbitrarily chosen, since the removing of the emplaced compensating joint-pins 61', 62',... 6 (n-) k' containing foil strips and changing to an armouring thereof, shall be allowed by the tixothrope material.

Figure 3. shows an axial section of the structural arrangement of the 13 type <BR> <BR> <BR> <BR> <BR> curtain-wall completed according to method of the invention, when a foil board 4n-1 is being hammered down between the borings 2n, 2n, by means of cutting edge 8 attached to the bottom thereof, intersecting the inner space of the borings 21,2n+,, and forming the narrow gap 3n-1.

Force lines 9 indicated in the Figure 3. are symbolising the applied beetle-rods 12 exerting a force onto the ends 8a, 8b of the cutting edge 8. In the Figure 3. there is shown only a theoretical arrangement, the practically applied cutting edges 8 have some striking plates having a gradually increasing cross-section advantageously to obtain the minimal resistance and to eliminate the dowel effect.

The ends 8a, 8b of the cutting edges 8 remaining in the soil 1 are formed to seat <BR> <BR> <BR> <BR> <BR> and fit together with the adjacent ends 8a, 8b of cutting edge 8 of foil boards 41... 4n hammered down into the same depth.

The theoretical arrangement of the Figure 3. is drawn to scale compared to the <BR> <BR> <BR> <BR> <BR> practically completed cutoff. Applying foil boards 41,... 4n having a few mm of thickness, the distance of borings 21,2nazi lies of the order of meter, while the order of diameter of

borings 21,2nazi must be chosen depending on the depth of the cutoff to obtain a buckling less than the permissible value.

Figure 4. shows the theoretical arrangement of the beetle-rod 12 applied to realise the method according to the invention.

In this case the facets 13 of the beetle-rod 12 are formed by steel sheets radially extending into the centreline and forming an angle a between them, the cross-ribs 14 of the beetle-rod 12 are also steel sheets incurvated to follow the shape of borings 21,22,23,... 2n, and connecting two facets 13 forming an angle a therebetween.

The bottom end of the facets 13 comprise an adequately large face 15 being adjacent the centreline of the beetle-rod 12 to seat reliably to the end 8a, 8b of the cutting edge 8 and to transmit the force.

Summarising the described method in a few words, the advantages of the solution of the present invention inhere in that, that the compaction of the side wall of the gap and the hammering down the water-proof curtain-wall take place at the same time (contemporaneously) to obtain a narrow cutoff formed by means of driving technology and without soil 1 excavation, and so that the longitudinally acting friction force shall be negligibly small compared to the sliding resistance of the cutting edge 8. in this way 20-30 m deep, water-proof cutoffs may be built.

Compensating joint-pins 61,... 6n1 placed into borings 21,... 2nazi (into facets 15) filled with tixothrope slush-bentonite suspension-go by the occasional bias of the curtain walls, and accommodate also the dimensional deviations due to the bias of the borings 21,... 2n+1.

This factors allow to create an excellent water-proof, load-bearing and economically advantageous cutoff.