IMPROVEMENTS IN OR RELATING TO JOINTS BETWEEN CONCRETE ELEMENTS

Abstract: The disclosure relates to joints between a pair of elements such as a pair of concrete tunnel lining segments (10) which are secured together in compression by a fastening arrangement (13, 14) with a gasket (12) between the end faces (11) of the segments. The gasket has a multiplicity of spaced aperture (17) to prevent the gasket from creating a surface tension in the end faces (11) when the joint is subjected to compression.

Description: This invention relates to joints between elements at least one of which is formed from concrete such as joints between circumferential and axially extending edge faces of arcuate concrete tunnel lining segments, (see GB-A-2004931). The invention provides a joint between a pair of elements at least one of which is formed from concrete (e.g. arcuate concrete tunnel lining segments) comprising a gasket (or other packing) to engage between a pair of faces of the elements with the gasket in compression to provide a joint between the elements, wherein the gasket is formed with a plurality of apertures or surface recesses or surface projections in regions of the gasket which lie between the faces of the concrete elements to minimise application of any tensile force to said surface of the or each element when the gasket is compressed by said elements. In the case where the elements are secured together by connecting means extending between said faces of the elements, openings may be provided in the gasket through which the connecting means may pass. The following is a specific description of some embodiments of the invention, reference being made to the accompanying drawing in which: Figure 1 is a perspective view of a joint between two arcuate concrete lining segments embodying an apertured gasket; Figure 2 is a section through the encircle part of the gasket of Figure 1; Figure 3 is a similar view to that of Figure 2 showing a modified form of the gasket; and Figure 4 is a similar view to that of Figure 1 showing the invention applied to an alternative form of segment. Referring firstly to Figures 1 and 2 the drawings, there is shown a pair of arcuate concrete tunnel lining segments 10 having axially extending end faces 11 to be secured together with a bitumen or other similar material gasket 12 disposed between the faces. The concrete elements are connected together by a system described and illustrated in GB-A-2004931 and known as the "one pass" system. Briefly the system comprises pairs of semi-cylindrical recesses 13 cast in the end faces 11 of the segments and extending part way across the segment faces from the inner concave sides thereof. One of the semi-cylindrical recesses is bridged by an upstanding pair of hoops 14 and the other recesses bridged by a single upstanding hoop 15. The gasket 12 is formed with rectangular openings 16 in the way to align with the recesses 13 when the two segments 10 are brought together and, the hoops on the respective segments project through the openings 16 with the pair of hoops 14 receiving between them the single hoop 15 of the other segment and vice versa. Expandable fastening devices are then driven through the overlapping hoops to clamp the segments with a substantial compressive force against the gasket 12 to create a seal joint between the segment faces. The gasket 12 is formed with a multiplicity of apertures 17 or projections 18 shown in detail in Figure 2 and 3 in the areas of the gasket which engage between the faces 11 of the segment spaced from the openings 16 to prevent the gasket from creating a surface tension in the faces 11 of the concrete elements whilst under compression. The apertures or recesses also help to distribute compression when there is any uneveness in the surfaces of the concrete elements. An alternative construction is shown in Figure 3 in which the gasket has surface projections 18 on either side to serve the same purpose as the apertures 17. As indicated above, the arrangement is particularly applicable to arcuate concrete tunnel lining segments and it is frequently the case that maximum compressive forces arise in the joints between such segments through ground loadings and not by mechanical joint fixings. For example, tunnels which are at great depths in poor ground or which have large buildings or railway lines or the like above them, have much greater loads to contend with than tunnels nearer the surface which run through open ground. Any securing means between the segments may exert only a very small fraction of the compressive forces and the form of gasket indicated above for use between the adjacent faces of the segments is applicable whether or not securing means is provided. Figure 4 shows a further arrangement in which the segments 10 are secured together by bolts which pass through holes 19 in the segment ends and corresponding holes (openings) 20 in the gasket 12. It will be appreciated that the invention is equally applicable to joints between pairs of elements in which only one of the pair is formed from concrete and the other is formed, for example, from steel and irrespective of the design or securing means or type of joint.

Claims: A joint between a pair of elements (10) at least one of which is formed from concrete comprising a gasket (12) to engage between a pair of faces (11) of the elements with the gasket in compression to provide a joint between the elements, characterised in that the gasket (12) is formed with a plurality of apertures, (17) or surface recesses or surface projections (18) in regions of the gasket which lie between the faces (11) of the elements (10) to minimise application of any tensile force to the surface of the or each concrete element when the gasket is compressed by said elements. A joint as claimed in Claim 1, wherein the connecting means (14,15) between the elements extend through said faces of the elements and through corresponding openings (16,20) in the gasket and said apertures or recesses are formed in parts of the gaskets spaced from said openings.

Inventors: MITCHELL, SAMUEL BAILEY HART
Applicants: CHARCON TUNNELS LIMITED
Application year: 1989
Main classification: E21D11
IPC codes: E21D11