IMPROVEMENTS IN OR RELATING TO TUNNEL LINING SEGMENTS AND TUNNEL LININGS FORMED THEREFROM

Abstract: A cast-iron tunnel lining segment (10) of generally rectangular configuration having two opposite edges arranged in use to face axially of the tunnel lining, and the alternative two opposite edges (8,9) arranged in use to face circumferentially of the tunnel lining, the segment being curved in the circumferential direction concave inwardly; the circumferentially facing edges of the segment being provided with flanges (6,7) disposed adjacent thereto, and adapted to receive means for interconnecting the segment with other circumferentially adjacent segments, the flanges (6,7) being directed inwardly of the segment and each connecting with the inner side of the segment at a root inset from the circumferential edge of the segment; and a plurality of ribs (12-16) extending from the flanges to the adjacent circumferentially facing edges of the segment, the ribs being machined on their circumferentially facing edges to provide radially aligned surfaces adapted to engage with corresponding surfaces of circumferentially adjacent segments to form a lining ring, and strengthening rib continuations of said ribs extending between the flanges disposed adjacent the circumferentially facing edges of the segment.

Description: This invention relates to tunnel lining segments and tunnel linings formed therefrom. It is known to produce cast-iron tunnel segments connected together by bolted flanged joints. Such segments are usually connected together to form a ring which is then connected to successive rings within the bored or cut tunnel below ground, for example. Such segments are usually in the form of generally rectangular members having walls or edges arranged to face axially of the tunnel lining to be formed and walls or edges arranged to face circumferentially of the lining to be formed. For interconnection of the segments, flanges are usually provided at all four sides, extending inwardly of each segment. The circumferentially facing edges and flanges which are interconnected by means of nuts and bolts (for example) to form the complete rings of the lining, are required to transmit the hoop compressive thrust exerted by the surrounding ground and to transmit the bending moments induced by differential ground movements. The outer faces of the circumferentially facing flanges are usually machined flat to extend radially of the lining ring and provide a large bearing area covering (at least) most of the flange face. In order to cast mould the flanges without the use of expensive cores, it has hitherto been necessary for the flanges to be extravagantly thick (with respect to weight and cost) at their root connection with the inner side of the segment. In addition with such an arrangement it is necessary to provide a considerable amount of excess metal on the outward face of each of the flanges in order to ensure that segments can be machined to the precise required dimensions and angle. It is an object of the present invention to overcome or at least substantially reduced the above-­ mentioned disadvantages. In accordance with the invention there is provided a cast-iron tunnel segment of generally rectangular configuration having two opposite edges arranged in use to face axially of the tunnel lining, and the alternate two opposite edges arranged in use to face circumferentially of the tunnel lining, the segment being curved in the circumferential direction concave inwardly; the circumferentially facing edges of the segment being provided with flanges disposed adjacent thereto, and adapted to receive means for interconnecting the segment with other circumferentially adjacent segments, the flanges being directed inwardly of the segment and each connecting with the inner side of the segment at a root inset from the circumferential edge of the segment; and a plurality of ribs extending from the flanges to the adjacent circumferentially facing edges of the segment, the ribs being machined on their circumferentially facing edges to provide radially aligned surfaces adapted to engage with corresponding surfaces of circumferentially adjacent segments to form a lining ring, and strengthening rib continuations of said ribs extending between the flanges disposed adjacent the circumferentially facing edges of the segment. The invention includes within its scope tunnel linings incorporating a segment as herein defined. In order that the invention may be more readily understood, one embodiment thereof will now be described with reference to the accompanying drawings in which:- Figure 1 is an axial end elevation of one form of prior art tunnel lining segment; Figure 2 is an axial end elevation of a tunnel lining segment in accordance with the invention; Figure 3 is a section on the line B-B of Figure 2; and Figure 4 is a view on arrow A of Figure 2. As can be seen from Figure 1, the prior art cast-­ iron segment 1 illustrated has circumferentially facing inwardly directed flanges 2, 3 having outer faces 4, 5 machined flat and radially aligned to provide a large bearing area covering most of the flange face with respect to adjacent circumferential segments. As previously mentioned, such flanges require the use of expensive cores (as illustrated) or are extravagantly thick at their root connection with the segment, and additionally a considerable excess of iron must be provided on the outer flange faces 4 and 5 in order to ensure that the face can be machined for the required dimensions and curvature of the tunnel lining ring to be formed by connection of the segment to others. In contrast as can be seen in Figure 2, 3 and 4 corresponding flanges 6 and 7 of circumferentially facing edges 8 and 9 of a segment 10 according to the invention are set-back from the circumferentially facing edges 8 and 9 of the segment. The flanges need not be radially aligned, but can be set at a convenient disposition such as in the parallel arrangement illustrated. The axial ends of the segment are provided with inwardly directed flanges 11 and 19 at right-angles to the main body of the segment, and inwardly directed strengthening ribs 20, 21 and 22 are also provided along the axial length of the segment. As seen clearly in Figure 4 flanges 11 and 19 and ribs 20, 21 and 22 effectively extend through the circumferentially facing flanges into extension ribs 12, 13, 14, 15 and 16 which link the segment end to the flanges 6 and 7. The ends 17, 18 of the extension ribs and the edges 8 and 9 are machined for accurate radial alignment and for engagement with corresponding extension rib and segment ends on circumferentially adjacent tunnel segments to provide the required curvature of the tunnel lining. Nuts and bolts (not shown) may be utilised through bores (not shown) in the flanges 6, 7 and 11 for interconnection of the segment with adjacent segments. The just mentioned feature of abutment of the machined ends 17, 18 of the ribs and the edges 8 and 9 of segment 10 is of considerable importance, particularly the abutment of the ribs throughout their length, since in use bolts tightened between the flanges 6 and 7 of juxtaposed segments cause the flanges to act, in effect, as spring tensioning devices firmly holding together the totality of edges 17, 18 of the ribs and the edges 8 and 9 of segments 10, even under any bending stress due to distortion of the tunnel lining, for example, thereby providing a very firm positive connection between segments. It is to be noted that the abutment of the totality of ends and edges 17, 18 and 8, 9 most importantly enables uniform transmission of hoop thrust between segments when formed into the lining. In contrast in connectors of the kind shown in Figure 1 for example the connected flanges 2 and 3 of adjacent segments can, between the interconnecting bolts thereof, when subjected to bending stress for example, be susceptible to some separation due to a "hinge" effect of the flanges 2 and 3. Similarly a previous proposal for example, where the ends 17 and 18 of the ribs are largely concave along their length so that with connected segments, juxtaposed rib edges only meet at their tip and root, distortion of the ribs in question and their adjacent end flanges from the tension imposed by connecting bolts can occur, and more importantly, because of the significantly incomplete connection between the ends of abutting ribs, there is a detrimental lack of uniformity of transmission of hoop thrust therebetween. The invention is additionally beneficial in numerous ways. Thus for example the area of metal requiring machining for the accurate alignment of adjacent segments around the ring of the liner is reduced and so is confined to that which provides the useful function of transmitting the hoop compressive thrust via the ribs and axial end flanges. In addition the two set-back circumferentially facing flanges can, if disposed in a parallel arrangement as illustrated, simplify moulding by obviating the necessity for large cores and enabling the flange thickness to be reduced at the root. The invention also improves the efficiency of the thrust transfer between segments and simplifies, lightens and cheapens the product. The invention is particularly beneficial when applied to linings made from a large number of relatively small segments such as can be manufactured economically on automated cast moulding machines.

Claims: 1. A cast-iron tunnel lining segment of generally rectangular configuration having two opposite edges arranged in use to face axially of the tunnel lining, and the alternate two opposite edges arranged in use to face circumferentially of the tunnel lining, the segment being curved in the circumferential direction concave inwardly; the circumferentially facing edges of the segment being provided with flanges disposed adjacent thereto, and adapted to receive means for interconnecting the segment with other circumferentially adjacent segments, the flanges being directed inwardly of the segment and each connecting with the inner side of the segment at a root inset from the circumferential edge of the segment; and a plurality of ribs extending from the flanges to the adjacent circumferentially facing edges of the segment, the ribs being machined on their circumferentially facing edges to provide radially aligned surfaces adapted to engage with corresponding surfaces of circumferentially adjacent segments to form a lining ring, and strengthening rib continuations of said ribs extending between the flanges disposed adjacent the circumferentially facing edges of the segment. 2. A segment as claimed in Claim 1 wherein the flanges disposed adjacent the circumferentially facing edges of the segment lie in generally parallel planes. 3. A segment as claimed in Claim 2 wherein the dimension and curvature of the segment and the dimensions of the flanges are such that the machined circumferentially facing edges of the flanges taper to adjacent the innermost ends of the flanges. 4. A segment as claimed in Claim 1 or 2 formed of spheroidal graphite iron. 5. A tunnel lining incorporating a segment as claimed in any one of the preceding claims.

Inventors: CURTIS, DAVID JOHN, GREATOREX, CYRIL BARRIE
Applicants: STANTON PLC
Application year: 1987
Main classification: E21D11
IPC codes: F16L9, E21D11