GB1559102A

GB1559102A - Reinforced concrete tubbing and sealing tape and combination

Info

Publication number: GB1559102A
Application number: GB39221/76A
Authority: GB
Original assignee: Ruhrkohle AG
Current assignee: RAG AG
Priority date: 1975-09-26
Filing date: 1976-09-22
Publication date: 1980-01-16
Also published as: DE2542912B2; DE2542912A1; DE2542912C3; ZA763214B; ATA700376A; AT356168B; CH610971A5

Abstract

The waterbar (6) for sealing structural parts is arranged in a groove of one structural part (2) and has a concave underside (8) which is directed towards the base surface (5) of the groove. The thickness of the waterbar is smallest at the centre. In this arrangement, the waterbar constitutes a flexural resilient element, thus making it easier to compress the waterbar when screwing structural parts together while, at the same time, achieving a very good sealing effect. <IMAGE>

Description

(54) REINFORCED CONCRETE TUBBING AND SEALING TAPE COMBINATION (71) We, RUHRKOHLE AETIENGESELL- SCHAFT, a Germany Company, of Rellinghauser Strasse 1, D-4300 Essen, Germany, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to the sealing of joints between adjoining tubbings of reinforced concrete which have, on their mutually opposite end surfaces, at least one groove which receives a sealing tape and which when initially fitted projects from the groove. The invention provides a combination of a reinforced concrete tubbing and a sealing ring of novel shape.

The invention is particularly, but not exclusively, applicable to tubbingtsealing tape combinations which employ tapes of thermoplastics material having partially elastomeric properties: that is to say, tapes which after having been compressed, for example to 10% of their original thickness, resiliently recover the original thickness, all but a few per cent, at the latest after several days have elapsed. Such behaviour of the material is also called visco-elasticity and is in contrast to plastics which exhibit cold flow and do not resiliently return to their initial state after such extreme deformation.

In particular, visco-elastic behaviour of this kind is exhibited by bituminous sealing material which contains an ethylene copolymer and comprises, to the extent of about 45 - 50% by weight, a mixture which has a stress cracking value of about 6,000 hours and consists of ethylene copolymer and a small proportion of bitumen, and to the extent of about 40% by weight, anthracite dust which, if appropriate, contains 30% by weight of ash (based on the proportion of anthracite dust) and, if appropriate, has a particle size of 30y, the remainder being made up of high-pressure polyethylene (German Offenlegungsschrift No. 2,156,782).

Tubbings of reinforced concrete which are bolted to one another, represent the preferred field of application of the invention. If tubbings of this type are sealed with a visco-elastic material of approximately the above composition, the sealing tape tends, due to its high resilience, to follow movements of the strata and to reseal the joint again. However, care must be taken that, on the one hand, the compressions which arise at the edges of the groove in the compressed state of the sealing tape remain large enough, after the creep process has ended, to provide a seal which is still adequately reliable against a precalculated water pressure on the tubbings and that, on the other hand, the edge faces of the groove, which are weak from the point of view of reinforced concrete technology, are not unduly stressed when the restoring forces are activated.The compression forces are provided by the bolts of the tubbings. These forces must be sufficiently high that they are able to provide the necessary restoring forces, taking into account their diminution due to creep of the sealing tape material.

Moreover, reinforced concrete tubbings are also superior to steel tubbings in that they permit an exact calculation of the restoring forces of the joint tape. One of the reasons for this is that, negleeting the effect of operating temperatures, the creep of steels is in some cases higher than that of sealing tapes, in particular when the latter consist of the material described above, and that, according to experience, the creep of steels has still not reached a state of equilibrium after approximately 25 years, whilst in the case of visco-elastic materials of the type above described, creep has already finished after seven years.

Sealing tapes, of the general shape initially described, for sealing tubbings of rein forced concrete are known. The underside, which engages the pIane base surface of the groove, of the sealing tape has parallel groove-type recesses so that, in the region of this surface of the sealing tape, the contour line of the cross-section of the sealing tape has a toothed appearance. These teeth are meant to increase the restoring forces in the sealing tape. Furthermore, the sealing tape consists of an elastomeric material.

The lateral side surfaces of the known sealing tape run parallel to the lateral surfaces of the joint. The edge zones of the top side of the sealing tape are tapered so that the thickness of the sealing tape decreases towards the edges. Finally, the sealing tape has a projection so that the top side of the sealing tape can support the adjacent sealing tape of the adjoining tubbing.

It has been found that very considerable forces must be applied by the said bolts of the tubbings in order to generate the requisite restoring forces in the sealing tape.

In fact, linear pressures of 5 - 10 tonneslm are used here in order to ensure the requisite long-term safety. The application of forces of such magnitude is difficult and expensive. Furthermore, it proves to be a disadvantage that the pressure is particularly high on the lateral surfaces of the joint. Finally, when the tubbings are pressed together, concrete or cement slurry sometimes gets between the teeth of the profile of the joint tape and in parts defeats their intended action.

The invention is based on the discovery that these disadvantages including those related to the particularly high linear pressures, are in the main a problem resulting from the incorrect design of the shape of the sealing tape and are only in part a problem of unsuitable materials. Accordingly, it is the object of the invention to achieve a reduction of the linear pressures by means of a novel shape of the sealing tape and, in a further development, to achieve a reduction of the stress on the side walls of the groove.

According to the invention there is provided the combination of a tubbing of reinforced concrete and a sealing tape of resilient material adapted to be received within an end surface groove of the tubbing for the purpose of sealing the latter with respect to an opposite end of an adjacent tubbing, which groove is delimited by substantially flat side and base surfaces, wherein the sealing tape is so dimensioned that when seated in the groove in an uncompressed state it projects from the groove and has a concave inner surface for engagement with the base surface of the groove, which inner surface is of curved form such that the thickness of the tape increases from the centre thereof to the edges of the inner surface and the free space between the inner tape surface and the base surface of the groove measured at the centre of the tape is substantially the same as the projection of the tape from the groove.

When shaped in this manner, the sealing tape represents a flexible resilient body.

As the inner surface of the sealing tape forms a cavity before the tape is compressed, the tape when in the uncompressed state is linearly seated in the groove only by its inner edges. Appropriate mathematical comparisons show that as generatrix for the curved inner tape surface 4th order parabolas are most advantageous. The distance between the inner surface of the sealing tape and the base surface of the groove, measured at the centre of the tape when seated in the groove and in the uncompressed state, then preferably exactly equals the dimension of the projection of the tape from the proove. The thickness of the tape profile then continuously increases towards the edges of the sealing tape from the centre.

When such a sealing tape has been inserted into the groove, the initial effect of the joint compression force applied, for example the tightening forces of the joint bolts, is to press the sealing tape profile down on to the base of the groove with the introduction of bending stresses. Only after this has occurred does the continuing application of the joint compression force result in compression of the sealing tape by means of contact pressure. It can be shown that, with the selected shape of the sealing tape according to the invention, the applied compressive force (generating the compressive stress cr,) amounts to only about 2.8 times the initial force which is necessary to press the sealing tape down on to the base of the groove. The total force to be applied by the joint bolts is composed of the sum of these two forces.In a practical illustrative embodiment of the invention this total force is approximately 6.4 kp/m, the proportion of the compressive force amounting to approximately 4.7 kplm.

Preferably the shape of the sealing tape is further improved by providing, in each of the lateral side surfaces of the tape, a recess which extends from the corresponding inner side edge over substantially two thirds of the thickness of the tape, this recess being of uniform profile along the length of tape. Preferably the transition from the recess into the outer third of the corresponding side surface is rounded.

After insertion of the sealing tape into the groove there is at first an open gap between the sealing tape and the lateral surfaces of the groove, as a result of the recesses, which have been described, in the inner two thirds of the sides of the tape.

The width of the two gaps corresponds to the depth of the recesses. This is selected so that the gap prevents a transmission of forces and is of a sufficient size to take up the extensions resulting from the transverse contraction of the joint tape. On the other hand, there is full contact between the joint tape and the groove in the outer region of the lateral surfaces of the groove, where the compressions are also sufficient to ensure a seal against water pressures which may occur. The advantage of this design of the joint tape is that the edge zones of the groove, which are weak from the point of view of reinforced concrete technology, are relieved of load.

It is, however, possible yet further to reduce the total compression, for example the tensile force of the bolts, without having to reduce the modulus of elasticity of the material of the sealing tape. Since the force, which is required to compress the flexing resilient body, cannot be reduced the problem is to lower the proportion of compressive force in the total applied force.

This problem can be solved by reducing the size of the surfaces which carry the load.

For this purpose, a further embodiment of the invention provides that the top outer side of the surface of the sealing tape while being symmetrical, about a longitudinal centre line has two parallel longitudinal grooves which separate a centre strip, and two edge strips located one on each side of the centre strip, each of the three strips presenting a surface area which is flat and normal to the lateral side surfaces of the tape. Preferably each of these grooves has an inclined base surface rising towards the centre strip.

It can be shown that, in the above-mentioned numerical example, the compressive force can once again be reduced by about 2.5 kplm.

The details, features and advantages of the invention will be clearly seen from the following description of illustrative embodiments given, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a cross-section of a tubbing groove and sealing tape according to one embodiment of the invention, with the tape inserted into the groove; Figure 2 shows, in a representation corresponding to Figure 1, the tubbingitape combination shown therein, after the resilient tape has been compressed; and Figure 3 shows, in a representation corresponding to Figure 1, a modified embodiment of the invention.

A groove is present in the end surface 1 of a tubbing 2 of reinforced concrete. The groove has substantially flat lateral surfaces 3 and 4 and a base suface 5 which is likewise substantially flat. The surface 1 is one of four end surfaces of the tubbing, all of which are provided with the groove shown and are in a position opposite to the correspondingly shaped end surfaces of adjacent tubbings. According to the illustrative embodiment these tubbings are bolted to one another. However, the bolts are not shown. The tensile forces applied in the bolts can be expressed as a total force applied per unit of length.

A sealing tape 6 is located in the groove.

It has a solid uniform cross-section, as can be seen in profile from the representations in the figures.

The sealing tape consists of the viscoelastic material which has been described initially and which has a modulus of elasticity of compression of Ed = 120 kplcm2 and a transverse contraction coefficient of ii = 0.47. A material of this type is to be regarded as particularly suitable for realising the invention in practice.

According to the illustrative embodiment in Figures 1 and 2, the sealing tape has a flat top side or outer surface 7. The latter projects from the groove beyond the end surface 1 to the extent of a projection represented at to. The underside 8 of the tape presents an inner surface for engagement with the base surface 5 of the groove.

The symmetrical inner surface 8 is of hollow curved form. As can be seen from Figures 1 and 3, the thickness of the sealing tape increases from the centre-on the central axis of symmetry which may be referred to as the profile axis 9-towards the edges of the inner tape surface or lateral side surfaces of the tape. In the initial uncompressed state, the edges 10 and 11 of the sealing tape 6 thus rest on the base surface 5 of the groove. Identical recesses 12 and 13 are present in the two lateral side surfaces of the sealing tape 6. Each of these recesses has a height given by the dimension h. This height amounts to approximately two thirds of the total height or thickness of the tape which is given as H.

Consequently a gap, designated as s, remains in the lower or inner two thirds of the side wall 3 of the groove between this side wall and the side wall 15 of the recess 12. The transition 16 from the recess 12 into the upper or outer third of the lateral side surface 17 of the tape is rounded. Only the lateral surface 17 outwardly of the recess 12 is in contact with the lateral surface 3 of the groove.

After the compression of the tape, a gap s' still remains between the inner limit or side wall 15 of each recess 12 or 13 and the corresponding facing surface of the side wall 3 of the groove. Consequently, no forces are transmitted here. On the other hand, the underside or inner surface 8 which faces the base surface 5 of the groove is pressed into face-to-face engagement with this base surface. The distance a which, in the uncompressed state of the sealing tape 6, is maintained between the underside 8 of the tape and the base surface 5 of the groove, measured at the centre of the tape, i.e. on the axis 9, is substantially the same as the projection to and has been taken up on compression of the tape in Figure 2.

The generatrix of the underside inner surface 8 is a 4th order parabola so that the thickness of the joint tape continuously increases from the centre, defined by the profile axis 9, towards the edges of the tape.

The following text gives a numerical example which makes it possible to appreciate the magnitude of the forces arising when the initially described material is used for the sealing tape.

In order to prevent the compressive forces from becoming excessive and nevertheless to obtain a reasonable size of projection, the latter amounts in this illustrative embodiment, with a depth of the groove of 1.2 cm, to one fifth of this value, that is to say to = 0.24 cm. and a then also is 0.24 cm. Along the lateral surfaces 3,4 of the groove, it is intended that the total compression applying thereon be kept small, and the width of the gap here is s = 0.2 cm at each of the lateral side surfaces 3A of the groove. This gap is sufficiently large to prevent a transmission of forces over the corresponding depth of the tape, as shown in Figure 2, and to take up the extensions resulting from the transverse contraction.

The width b of the groove is 5.2 cm.

The above indicated tensile forces in the bolts can be calculated from these values and the known characteristics of the tape material.

In the illustrative embodiment according to Figure 3, the same reference numerals are used for identical parts. The sealing tape 6 represented in Figure 3 merely differs in that its top outer side is "toothed".

A centre strip 20 of the outer tape surface has a flat top side 21 and is subdivided into two equal halves by the profile axis 9, the outer surface being symmetrical about a longitudinal centre line. Its surface 21 runs perpendicularly or normal to the lateral side surfaces 22 or 23 of the sealing tape 6.

An edge strip 24 or 25 is located on each side of the centre strip 20, Each of the two edge strips also has a top side 26 or 27 which runs perpendicularly to the lateral side surface 22 or 23, is in turn flat and is flush with the top side 21 of the centre strip 20. Furthermore, each edge strip 24 or 25 is separated from the centre strip 20 by a corresponding longitudinal groove or recess 28 or 29 which has an inclined base surface 30 or 31 rising towards the centre strip 20.

WHAT WE CLAIM IS: 1. The combination of a tubbing of reinforced concrete and a sealing tape of resilient material adapted to be received within an end surface groove of the tubbing for the purpose of sealing the latter with respect to an opposite end of an adjacent tubbing, which groove is delimited by substantially flat side and base surfaces, wherein the sealing tape is so dimensioned that when seated in the groove in an uncompressed state it projects from the groove and has a concave inner surface for engagement with the base surface of the groove, which inner surface is of curved form such that the thickness of the tape increases from the centre thereof to the edges of the inner surface and the free space between the inner tape surface and the base surface of the groove measured at the centre of the tape is substantially the same as the projection of the tape from the groove.

2. A combination as claimed in claim 1, wherein the generatrix of said curved inner surface of the tape is a 4th order parabola and the thickness of the tape continuously increases from the centre to the edges of that surface.

3. A combination according to claim 1 or 2, wherein said projection and free space are substantially equal to one fifth of the depth of the groove.

4. A combination according to any one of the preceding claims, wherein the tape has side recesses which extend from the inner side edges of the tape over substantially two thirds of the thickness thereof, these recesses being of uniform profile along the length of the tape.

5. A combination according to claim 4, wherein there is a rounded transition from each side recess into the outer third of the corresponding side surface.

6. A combination according to ony one of the preceding claims, wherein the outer surface of the tape opposite to said inner surface thereof is flat.

7. A combination according to any one of claims 1 to 5, wherein the outer surface of the tape opposite to said inner surface thereof is symmetrical about a longitudinal centre line and has two parallel longitudinal grooves which separate a centre strip and two edge strips, each of these three strips presenting a surface area which is flat and normal to lateral side surfaces of the tape.

8. A combination according to claim 7, wherein the grooves in the outer surface of the tape have inclined base surfaces which rise towards the centre strip.

9. A combination according to any one of the preceding claims, wherein the tubbing thereof is joined to an adjacent tubbing and the sealing strip of the combination

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which faces the base surface 5 of the groove is pressed into face-to-face engagement with this base surface. The distance a which, in the uncompressed state of the sealing tape 6, is maintained between the underside 8 of the tape and the base surface 5 of the groove, measured at the centre of the tape, i.e. on the axis 9, is substantially the same as the projection to and has been taken up on compression of the tape in Figure 2. The generatrix of the underside inner surface 8 is a 4th order parabola so that the thickness of the joint tape continuously increases from the centre, defined by the profile axis 9, towards the edges of the tape. The following text gives a numerical example which makes it possible to appreciate the magnitude of the forces arising when the initially described material is used for the sealing tape. In order to prevent the compressive forces from becoming excessive and nevertheless to obtain a reasonable size of projection, the latter amounts in this illustrative embodiment, with a depth of the groove of 1.2 cm, to one fifth of this value, that is to say to = 0.24 cm. and a then also is 0.24 cm. Along the lateral surfaces 3,4 of the groove, it is intended that the total compression applying thereon be kept small, and the width of the gap here is s = 0.2 cm at each of the lateral side surfaces 3A of the groove. This gap is sufficiently large to prevent a transmission of forces over the corresponding depth of the tape, as shown in Figure 2, and to take up the extensions resulting from the transverse contraction. The width b of the groove is 5.2 cm. The above indicated tensile forces in the bolts can be calculated from these values and the known characteristics of the tape material. In the illustrative embodiment according to Figure 3, the same reference numerals are used for identical parts. The sealing tape 6 represented in Figure 3 merely differs in that its top outer side is "toothed". A centre strip 20 of the outer tape surface has a flat top side 21 and is subdivided into two equal halves by the profile axis 9, the outer surface being symmetrical about a longitudinal centre line. Its surface 21 runs perpendicularly or normal to the lateral side surfaces 22 or 23 of the sealing tape 6. An edge strip 24 or 25 is located on each side of the centre strip 20, Each of the two edge strips also has a top side 26 or 27 which runs perpendicularly to the lateral side surface 22 or 23, is in turn flat and is flush with the top side 21 of the centre strip 20. Furthermore, each edge strip 24 or 25 is separated from the centre strip 20 by a corresponding longitudinal groove or recess 28 or 29 which has an inclined base surface 30 or 31 rising towards the centre strip 20. WHAT WE CLAIM IS:

1. The combination of a tubbing of reinforced concrete and a sealing tape of resilient material adapted to be received within an end surface groove of the tubbing for the purpose of sealing the latter with respect to an opposite end of an adjacent tubbing, which groove is delimited by substantially flat side and base surfaces, wherein the sealing tape is so dimensioned that when seated in the groove in an uncompressed state it projects from the groove and has a concave inner surface for engagement with the base surface of the groove, which inner surface is of curved form such that the thickness of the tape increases from the centre thereof to the edges of the inner surface and the free space between the inner tape surface and the base surface of the groove measured at the centre of the tape is substantially the same as the projection of the tape from the groove.

supports an adjacent sealing strip associated with the adjacent tubbing.

10. A tubbing and sealing tape combination, substantially as herein particularly described with reference to Figures 1 and 2, or Figure 3, of the accompanying drawings.