DE7021646U - REINFORCEMENT BASKET FOR AN UNDERGROUND BARRIER WALL MADE OF REINFORCED CONCRETE FOR CIVIL ENGINEERING. - Google Patents

Description

Q 70 216 46.5
ICOS-Veder Grundbau

/ C reinforcement cage for an underground
Reinforced concrete barrier wall for civil engineering

The innovation concerns a wall slot excavated in the existing subsoil and forming the formwork Reinforcement cage that can be lowered and set in concrete for an underground bulkhead reinforced concrete for underground structures, for example for building pit enclosure or for underpasses, subway tunnels, underground garages or the like.

In the case of various types of underground structures, before excavation of the excavation pit, barrier walls - so-called * Schiitzwand * - are drawn in, which are attached to the excavation pit that is created later - subway tunnels or the like. - should support the B ^ ean on the side and prevent underground groundwater flows and also serve as a foundation.

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When creating such underground barrier walls, a trench of the desired depth and width is first made in the generally excavated in the presence of bentonite suspension and then filled with concrete «asphalt concrete or other hardening building material, with the natural side walls of the trench serve directly as formwork. In such barrier walls the occurring loads are now duroh - such as above all by earth pressure, water pressure and also also caused by the load - considerable tensions, so that the barrier walls are often made of reinforced concrete to achieve the required strength, the netall reinforcement being designed as a rigid reinforcement cage - be it made of normal structural steel or from those with increased adhesive strength. The earth pressure acting on the diaphragm wall forms naturally only at the point in time when the relevant construction pit, tunnel or the like, which is to be supported by the diaphragm wall, is excavated.

The dimensioning of the diaphragm walls - especially their thickness - depends on the required strength, however, the limits of internal stress permissible for concrete must be adhered to; in the presence of high earth pressures, the span of the diaphragm wall can can be reduced in size by pegging or anchoring. Furthermore, the diaphragm walls can also be designed with special cross-sectional shapes with a high moment of inertia, e.g. in sections with a T-shaped, H-shaped or also with an arched cross-section; in this way Cylindrical slotted walls with a circular or elliptical plan can also be constructed, whereby a particularly favorable interaction of the individual wall elements results. However, in civil engineering works the underground barrier walls are in many cases not built according to the above schemes, in which

the strength parameters fully meet the static requirements, - be it due to lack of space «for manufacturing or also for economic reasons.

According to the innovation, underground barrier walls of the type described at the beginning are now used for civil engineering works the disadvantages mentioned are effectively avoided by "that the reinforcement cage has lower transverse webs" which tension wires or cables are attached, which are attached at their free other end to adjustable supports are. So on a prepared, stiff, metal reinforcement cage steel wires or ropes arranged at a distance from one another essentially vertically and in a predetermined transverse position, preferably deflected towards the side of the intended excavation, lying loose individually or in groups, which steel wires or ropes - after inserting the reinforcement cage equipped in this way into the excavation for the diaphragm wall - with their lower end are attached to the slot sole. Furthermore, the steel wires or ropes are done after Setting of the poured concrete according to the known prestressed concrete principle from above under tension until the finished diaphragm wall has assumed a predetermined, permanent prebending towards the side of the existing soil, which means that in the existing soil even before the excavation on its other side is excavated a counter pressure is awakened.

The in this way inserted into the wall excavation, metal reinforcement cages .., on which the tensioning wires or ropes rest, can now be relatively simple and also very easy in a well-known manner be assembled. On these reinforcement cages - if necessary on special supports - the when the

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Trench wall to be braced vertically steel wires or ropes generally against the side of the later excavation after a predetermined - preferably in essentially similar to a sinus line curved - lines laid out, which from the in the diaphragm wall im special case caused bending conditions and in the different load phases of the Diaphragm wall should correspond to the restraint conditions occurring in the individual levels. In the simplest case, after lowering the reinforcement cage In the wall excavation, the tensioning wires or ropes lying loosely on this carrier with their lower end on the Base of excavated wall attached - preferably afterwards poured concrete itself over a certain distance, which on the one hand for the secure anchoring of the span iui Concrete is sufficient and, on the other hand, the main part of the steel wires or ropes after the concrete has set The head end of the diaphragm wall can be subjected to tensile stress with the desired effect; for fixing Of course, any suitable mechanical elements can also be used to attach the tensioning wires to the slot sole, which there for example were previously fixed by means of separate cement injections. These tensioning wires or ropes, which are firmly anchored to the bottom of the slot, naturally remain cast in the hardened, pre-tensioned concrete wall and are thus lost.

To explain the resulting with the innovation The method of manufacturing underground diaphragm walls is based on the following surprising findings The internal stresses occurring in the concrete are during the artificially applied prestressing of the tilitz wall

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lower than those, vr *, leh6, according to purely theoretical considerations, would correspond to the Ängewandt-ai: bending forces: in the case of such seated walls, in which the soil directly forms the formwork and is located there. "vn the side surface of the diaphragm wall clings particularly closely, this behavior of the concrete results from the soil reaction, which counteracts the pre-laying that occurs in the diaphragm wall at the moment of its formation; the horizontal pressure generated by the pre-bending of the diaphragm wall, directed against the existing subsoil therefore arouses in the ground immediately a substantially equal but opposite counter-pressure, through which the concrete training considerably reduced internal stresses and possibly even prevented Welch ¹ of the diaphragm wall the latter is after the formation of Vorverbiegung just by the algebraic sum of the artificial The state created in the concrete of the diaphragm wall by this vertical prestressing can thus be defined in such a way that in the concrete in the phase of the horizontal pre-bending in the various Internal stresses are stored deep in the diaphragm wall, which are then gradually released in the subsequent phase of excavation of the construction pit with the occurrence of the actual earth pressure, with the entire earth-side surface of the concrete wall permanently under compressive stress. Because the trench wall is still completely enclosed on both sides in the ground during the construction of the horizontal prebending, the prebending itself can also be designed in such a way that a corresponding soil reaction occurs on both surfaces of the trench wall; as a result, internal stresses can be dosed in different depths of the diaphragm wall at each individual point in such a way that βie by adding the during the excavation of the construction pit

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resulting, active, external _x-d pressure of any, Can assume certain values, which of course are within the safety limits of the concrete must lie; During the individual, successive construction phases, the concrete wall stands along its entire length Area always under pressure and therefore reacts as a whole.

A preferred embodiment of this underground barrier wall is designed such that on the one hand the prepared Excavation for the diaphragm wall on the side of the later excavation is profiled in sections in a T-shape or there vertical bulges are attached and that on the other hand the reinforcement cage with in these bulges engaging transverse webs is provided, on which the tensioning wires or ropes rest.

Furthermore, according to the innovation, the tensioning device intended for the production of such underground barrier walls is constructed in such a way that the tensioning wires or ropes resting on the reinforcement cage are loosely drawn into tubular guide sleeves and anchored to the base of the excavated wall at mechanical brackets, for example on ζ threads, hooks, claws or the like. are attached - preferably

wise detachable, so that after completion of the prestressed diaphragm wall, the tensioning wires or ropes from the concreted in Guide tubes can be pulled out again. These guide tubes with the loosely drawn-in tensioning wires or ropes can be designed as single-core. As tension wires or ropes - so which ones after Fulfill their task, namely the achievement of a stationary pre-bending of the diaphragm wall can be recovered can - thus steels of high quality with particularly good strength properties can be used, such as

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for example steel columns or other equivalent types of steel.

In an advantageous variant, the guide tubes are with the loosely drawn-in tensioning threads or ropes designed as loops connected at the bottom, on the one hand each Rohrsc.i _elf e with its lower end on the Base of the wall excavation - be it on a crossbar of the reinforcement cage itself, be it on a separate, stationary one anchored holding member - is attached and, on the other hand, the tension wire or the rope with both, from the Trench wall above protruding, free ends is connected to a pulling unit. With this two-lane arrangement are preferably the guide tubes resting on the reinforcement cage at two adjacent bracing points connected with the loosely drawn-in tensioning wires or ropes to form a pipe loop. In this training the Clamping device with guide tubes laid in two lanes and connected with a lower loop can be used in particularly in a simple way, the drawn-in tensioning wires or ropes after fulfilling their tensioning function to a new one Use to be recovered.

In this embodiment of the tensioning device with tensioning wires or ropes drawn into guide tubes For example, the adjusted cables are placed on the reinforcement cage before it is used in the excavated wall - that is the guide tubes with the drawn-in tensioning wires or ropes - are placed or fastened. But it can also expediently only the empty single-core or loop-shaped guide tubes attached to the reinforcement cage for the time being and only after the concrete has set, the tensioning wires or ropes are inserted into the concreted-in guide tubes become, which * the latter if arranged one on top of the other

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be releasably attached with their lower end to the bottom of the diaphragm wall. In this second case - with a single-core arrangement - the lower ends of the steel wires or ropes can either be fixedly anchored to the slot sole by means of cement injections or else be detachably connected to suitable mechanical fastening members.

In the case of the devices described here for underground barrier walls made in prestressed concrete structures can reduce the tension in the barrier wall χ Steel wires or ropes are carried out in a more efficient manner, that at the head end of the trench wall the above protruding ends of several adjacent tensioning wires or - Ropes each attached to a common 'x'rSger and are attached by means of the same to a -preferably operated hydraulic bell - pulling unit. The special one [The training and arrangement of the pulling units will, of course, depend on the existing building conditions in each individual case and working conditions adapted. In addition, on the underground reinforced concrete wall in the various Phases of excavation of the excavation or un * ~ er tent-related load conditions in the diaphragm wall used steel wires or ropes by resumption) of the tension of the same, also repeatedly or temporarily get abandoned. Finally, after completion of the underground barrier wall - i.e. when the concrete structure to absorb the intended normal loads -the steel wires inserted into the guide sleeves or - Ropes made of high-quality steel are permanently connected to the concrete mass - by inserting steel wires between the guide tubes and the drawn-in steel wires Cement injections - thereby ensuring the constant maintenance of the desired pre-connection of the diaphragm wall

j is guaranteed.

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When building the newly equipped, underground barrier walls, both those in the modern Civil engineering technology made high demands In more satisfactory We also achieved numerous, significant advantages · »namely the excavated wall slot can be narrower and thus the resisting cross-section smaller; the one used in the concrete wall Steel reinforcement is dimensioned lighter and can be largely reduced; those in the diaphragm wall at easier Tensions that occur in reinforced concrete are significantly reduced or even eliminated - in particular the tensile stresses, which is particularly important in the case of sealing walls which are exposed to aggressive water; compared to conventional reinforced concrete walls, there is a much more rational construction method and a considerable reduction the construction costs achieved; in addition, the possibility of using such underground barrier walls can also be extended to structures that have previously been technically very difficult or uneconomical or else could practically not be realized at all.

In the drawing are to explain the innovation according to Method for the production of underground barrier walls of civil engineering works three embodiments of illustrated by the same constructed diaphragm walls. It show: Pig »1 already has such a diaphragm wall excavated construction pit 5 - in vertical cross-section, wherein a single-core tensioning rope and a two-lane arrangement of the same with a lower connecting loop in Coverage are drawn on top of each other;

2a and 2b each have a horizontal cross-section through a simple seat wall or through one with T-shaped profiling of the excavated wall from sections

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as well as the reinforcement cage; and finally

3a * 3b and 3c different diagrams for explanation the stress curve in the concrete wall during the individual phases of its stress.

In the case of the in Flg. 1 and 2, the arrangement shown in both main sections, a barrier wall 1 made of reinforced concrete is drawn into a continuous wall slot excavated in the grown soil Q, which is intended to support the soil on the side wall of the excavation pit 5 that is later excavated or to absorb the earth pressure T occurring there and also serves to prevent groundwater from flowing in. The reinforcement used in this diaphragm wall 1 is made """" a rigid basket 2 from structural steel, in which at the side of the pit 5 is a group of vertical steel wires or cables 3 in approximately equal intervals - in a predetermined, against the excavation In the embodiment shown here, these prestressing steels 3 are now loosely drawn into a guide tube 4 which, in turn, can be attached to the support points of the reinforcement cage 2 in the specified curvature position and, after the concrete has set, the underneath vertical tension-tension standing steel wires 3 allows a sliding movement in the longitudinal direction.

In the simplest case there are now the individual tension wires or ropes 3 with their lower end on the base of the wall excavation in holding members 5 of conventional design anchored there - for example in threaded parts, hooks, Claws or the like. - fixed, be it fixed or detachable; further are the vertical prestressing steels 3 on the Crown of the diaphragm wall 1 in adjustable holders or trays

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like 6 attached, by means of which the prestressing steels are held under tension after the cast concrete has set; Due to this longitudinal tensioning of the prestressing steels 3, a predetermined permanent pre-bending against the soil Q is achieved in the further course in the fully hardened concrete wall 1 and a corresponding counter pressure T is awakened by the resulting horizontal pressure P there. The clamping steels 3 can now, this train-Kraf c either permanently or tureh are subjected temporarily "ie until sufficient hardening of the concrete or until after completion of load-bearing of the blocking wall 1 by covering the excavated pit 5> for example, a subway tunnel; During the various construction phases, these tensile stresses imposed on the prestressing steels 3 can of course also be changed in adaptation to the respective pressure and loading conditions. Stationary fastening of the prestressing steel 3 at its lower end can also be carried out by concreting in the bottom of the slot - for example by additional cement injections introduced into the wall slot after the reinforcement cage 2 has been lowered. In the case of tensioning steels 3 drawn into guide tubes 4 - as already mentioned - a detachable fastening of the same to the slot base can also be considered, so that high-quality steels with optimal strength properties can also be used for this purpose, which after completion of the pre-tensioned diaphragm wall 1 with the Concrete guide tubes can be pulled out and thus recovered for further transformations.

Fig. 1 also shows a particularly advantageous embodiment of the bracing system in which the Guide tubes 4 with the loosely drawn-in prestressing steel 3

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are designed as loops connected at the bottom and Each such two-lane guide tube 4-4 with its lower tube loop 4 '"as indicated by a knitted pattern, at the Sciile des yand-Aushutjes is feefestist - be it either on a fixedly anchored holding member 5 or on a transverse web of the reinforcement cage 2 itself; Preferably, two vertical pipes 4, each resting on adjacent bracing points of the reinforcement cage 2, are connected to form a U-shaped pipe loop; With this arrangement, the pipes in the guide tubes 4 The existing prestressing steels 5 can be pulled out again in a particularly simple manner after the clamping has been completed.

In Flg. 2b shows a variant of the diaphragm wall in horizontal cross-section, in which, on the one hand, the wall excavation on the side of the later construction pit 5 is profiled in sections in a T-shape and, on the other hand, the reinforcement cage 2 is provided with transverse webs 2 * engaging in these bulges 1 * which the vertical prestressing steels y, preferably in groups, abut; With this special design, the vertical prestressing steels 3 can be laid out in a further arc and thus a greater internal leverage effect can be achieved for the steels under tension.

In Fig. 3a a barrier wall produced in conventional reinforced concrete construction is illustrated in horizontal cross section on the left - and the associated stress diagram is shown on the right, which shows the course of the stresses occurring in the barrier wall after the excavation of the subsequent excavation has taken place; In this concrete wall, the pressure zone β *, which adjoins the pending soil, is separated by the neutral line 7 from the - actually wider - tensile zone d, in which * the latter therefore only the metal reinforcement 8 acts.

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In the two pigs, b, b, and 3c, the stress conditions occurring therein are illustrated for a wall which is provided according to the innovation and which is provided with a lateral pre-bend directed towards the ground; Pig. 3b shows for such a diaphragm wall - which is subjected to the forces exerted by the tensioned steel wires 3 after the concrete has set - in the left diagram M the stress curve over the thickness of the diaphragm wall; in the middle diagram H * the course of those stresses is given which are caused in the diaphragm wall by the counterpressure caused by its lateral pre-bending in the soil; by superimposing or adding the two stress values M ₀ + M ¹ at each point of the cross-section, the stress diagram M _{1 is created} , according to which, as can be seen, only compressive forces occur over the entire cross-section of the diaphragm wall; finally shows Pig. 3c shows the stress curve occurring in the barrier wall during the excavation phase of the subsequent excavation: based on the one in PIg. 3b specified sum diagram M ₁ - consistently with

Compressive stresses S _n - when the excavation of the excavation begins, the full earth pressure gradually appears, which now generates the stresses indicated in the middle diagram M * 'over the thickness of the diaphragm wall; the superimposition of these two stresses M ₁ + M ¹¹ results in diagram M ₂ * which, compared to the initial diagram M ₁ , has the opposite course over the wall thickness, but there are again overall compressive stresses & . The combination of the two in Pig. ^{The middle diagrams M 1} and M ¹ 'shown in FIGS. 3b and 3c give the total effect of the earth pressure occurring in the soil.

Compared to underground barriers from the usual

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Reinforced concrete will be * »/ on according to the innovation produced barrier walls with lateral pre-bending achieves the following significant advantages: with constant Wall thickness, the section modulus can be increased to more than twice the value; further can next to one Wall of comparable thickness a considerably deeper excavation pit - up to over 50 # deeper - can be dug Diaphragm walls with special profiles of their cross-section can have these two values - section modulus or construction depth - can be increased even further; on the other hand, if the depth of the excavation remains the same, path

/ ", in the case of internal support or anchoring, considerable

created better working conditions. In each case, the number of to be attached to the diaphragm wall Supports, logging, etc. considerably reduced. Because in the concrete wall over the entire thickness exclusively Compressive stresses and tensile stresses no longer occur, the formation of cracks is excluded and thus the impermeability of the concrete wall to aggressive water ensures,. ', Finally, is also through use the more flexible and lighter prestressing steels make the installation of the reinforcement much easier and easier; before Above all, even with very deep diaphragm walls, the continuous flexible tensioning

* 'Steels, wires or ropes from supply rolls continu

This can also be done in low-ceilinged rooms - for example in basements or other objects with limited height - work can be carried out unhindered.

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Claims (3)

1. In a wall slot raised in the pending subsurface, which forms the formwork, can be lowered and concreted in Reinforcement cage for an underground barrier wall made of reinforced concrete for 'civil engineering works, for example for building pit closure or for UnterHihrungen, underground tunnels, underground garages Or the like., characterized in that the reinforcement cage (2) has lower transverse webs (5), to which tension wires or ropes (3) are attached, which are attached at their free other end to adjustable supports (6) are. "Reinforcement cage according to claim 1, characterized in that that the tension wires or cables are surrounded by tubular guide sleeves (4). 3. Reinforcement cage according to claim 2, characterized in that the guide sleeves (k) and the tensioning wires or cables (3) surrounded by them are single-core H. Reinforcement cage according to claim 2, characterized 702164630.12.71 shows that the guide sleeves (k) and the tensioning wires or ropes (3) they surround form a loop at the lower end, which is attached to the lower crossbars (5) of the reinforcement cage (2) » 70216A630.12.71