GB2166174A - Tunnelling shield - Google Patents

Abstract

A tunnelling shield has a forward part (12) shielding workers at the tunnel face and a rearward part (14) for the installation of tunnel lining. The two parts are articulated to follow tunnel contours and hydraulic rams are provided to set the angle between the two shield parts or spring loaded bolts are provided to bias the rearward part to the straight line position. <IMAGE>

Description

SPECIFICATION Tunnelling shield This invention relates to tunnelling shields.

In a long established tunnelling technique, a cylin drical tunnel shield is driven step-wise into the tunnel as workers within the shield dig into the tunnel face.

Annular sections oftunnel lining are installed behind the shield and the lining expanded to meetthetunnel wall or any annular gap between the lining and the shieldfilled with a suitable loose material. The tunnels are not necessarily straight and the hydraulic rams that are usually provided to drive the shield forward may be controlled so as to apply a force which is inclined to the shield axis. This approach is satisfactory with relatively broad tunnels and long radii of curvature but problems can be encountered with small bore tunnels (around two metres for example) where the shield necessarily has a high length to diameter ratio and is therefore not easily steered around tight curves.

It is an object of this invention to provide an improved tunnel shield which retains the low cost advantages of previous devices but which is better adapted to followtunnel contours.

Accordingly, the present invention consists in one aspect in a tunnelling shield comprising aforward shield partforthe protection of workers at the tunnel face; means for driving the shield partfor'.ardly into thetunnel; a rearward tail partservingforthe installation oftunnel lining behind the shield and connecting means between the shield and tail parts, the connecting means serving to transmittension and to provide for articulatory movement between the parts so enabling the shield to followtunnel contours.

Advantageoulsy, the connecting means further comprises setting means operable to control the relative orientation ofthe shield and tail parts.

Preferably, the setting means comprises at least one hydraulic ram having working parts connected to the shield part and tail part respectively.

Suitably, the connecting means comprises a plural ity of circumferentially spaced connectors, each connector being spring loaded.

In another aspect, the present invention consists in a tunnelling shield comprising aforward part, means for driving the forward part into a tunnel; a rearward part connected totheforward partfor articulation relative thereto and setting means operable to control the relative orientation of the shield parts.

Advantageously the drive means and setting means are interconnected so that a drive force applied preferentially atone point on the shield circumference is automatically accompanied by a separation ofthe shield parts at that point.

Suitably, the drive means comprises a plurality of circumferentially spaced hydraulic drive rams and the setting means comprises a like plurality of hydraulic setting rams respectively aligned with the drive rams.

Preferably, a plurality of control valves are provided, each valve controlling the supplyto one drive ram and to one setting ram.

The invention will now be described byway of example with reference to the accompanying draw ings in which: Figure lisa somewhat diagrammatic side view, partly in section, of a tunnelling shield according to this invention, Figure 2 is a sideviewto an enlarged scale showing part of the shield of Figure 1, and Figure 3 is a plan view to an enlarged scale showing a different part ofthe shield of Figure 1.

Thetunnelling shield shown generally at 10in Figure 1 comprises a forward shield part 12 and a rear ward tail part 14. In one examplethe shield hasa diameter of2 metres with a shield part length of 1.75 metres and a tail part length of 1 metre. A series of hydraulic drive rams 16 are securely mounted in the shield part and arranged circumferentially aboutthe inner periphery. Each ram 16 has a piston 18which extends through the tail part to engage the most recently installed tunnel lining section. In this way, the shield can be driven forwardly into the tunnel as workers protected bythe shield part 12 remove portions ofthe tunnel face.Hydraulic control means are provided in the shield to enable differential control ofthe rams which, in this example, may be six in number.

Referring nowto Figure 2, the shield and tail parts are not rigidly interconnected but are joined buy a ring of connectors 20 which permit a degree of articulatory motion between the parts. The slight gap between the parts isfilled by a seal 22 which may be of neoprene or other suitable material. Each connector comprises a bolt 24which extends rearward ly through a flange 26 provided at the inner end ofthe shield part. As shown in the drawing, the aperture 28 in this flange 26 may be ofconicalshape.Thebolt24passesthrough an aperture 30 in the opposing flange ofthe tail part 14.

This aperture is oversize and gives considerable clearance. Athrust washer 32 and spring washers 34 are provided on the bolt24 between the nut36 and the tail partflange.

Itwill be appreciated that as the shield part 12 is driven atan angle into a curved tunnel, thetail part 14 is able to adopt the appropriate orientation relative to the shield part by virtue ofthe clearance on the aperture 30. The substantial spring loading on the bolts ensures that the tail part is normally biassed to the straight line position and also serves to spread displacement forces around the circumference of the shield. In the preferred form there are approximately 50 bolts equallyspaced aroundtheshield.

Under certain conditions it is advantageous not merely to providefor articulation between the tail and shield parts but also to enable the relative orientation ofthe parts to be set.

Forth is purpose, there is shown in Figure 3 one of six control rams38which are provided atthe connection betweenthetail and shield parts. Each ram is rigidly secured to the shield part forwardly ofthe flange 26. The piston extendsforwardly and carries a yoke 40to which are connected two bolts 42. These extend rearwardlythrough apertures in both flanges and receive nuts 44. It will thus be seen that extension of anyone ram drawstogetherthetwo partsatthe location ofthe ram and, by selective operation of these control rams the angle between the shield and tail parts may be setwithinthe limits, of course, ofthe connectors 20.

In the preferred embodiment, each drive ram is twinned with the diametrically opposite setting ram and controlled through the same hydraulicvalve.

There is thus provided a bank of six hydrauliovaives and actuations of any one of these by the operator causes the shield to be urged forward at one point on the circumference with the shield and tail parts being drawn togetheratthe diametrically opposed point In practice, a number of valves will be operated together to give the required steering action.

By means ofthe present invention and the improved steering capability it provides, a more accurate tunnel can be cut and time is not wasted in re-positioning a shield than has diverted from the correct path through poor steering control.

It will be appreciated thatthis invention has been described by way of example only and a variety of modifications can be made without departing from the scope of the invention. Thus, it will be apparent to the skilled man that the described arrangement of bolts and clearance holes or slots is only one of a great numberof methods by which the desired degree of articulation can be provided whilsttransmitting tension. It will be possible, for example, to provide an annular cuff between the tail and shield parts with each part being capable of limited sliding movement relative to the cuff. In that arrangement, and possibly in others, the mounting and sealing functions are combined in one element. The diameter ofthe shield may clearly be altered as may the relative lengths of the two parts. In certain cases more than two parts will be provided. The described control rams or equivalent setting means which may control the relative orientation of the shield and tail portions are felt to be of great benefit but may not be essential underall circumstances. A shut off valve can usefully be provided in the described shield to isolate the setting rams when they are not required. Aiternatively, in some embodiments the setting rams may be omitted. When setting rams are provided,they may be connected so as to push ratherthan pull as described.

Claims (9)

1. Atunnelling shield comprising a forward shield partforthe protection of workers at the tunnel face; means for driving the shield part forwardly into the tunnel; a rearward tail part serving forthe installation oftunnel lining behind the shield and connecting means between the shield and tail parts, the connecting means serving to transmit tension and to provide for articulatory movement between the parts so enabling the shield to followtunnel contours.

2. Atunnelling shield according to Claim 1 wherein the connecting meansfurther comprises setting means operable to control the relative orientation of the shield and tail parts.

3. Atunnelling shield according to Claim 2, wherein the setting means comprises at least one hydrualic ram having working parts connected re spectivelyto the shield part and tail part.

4. Atunnelling shield according to any one ofthe preceding claims, wherein the connecting means comprises a plurality of circumferentially spaced connectors, each connector being spring loaded.

5. Atunnelling shield comprising forward part; meansfordrivingtheforward partintoatunnel;a rearward part connected to theforward partfor articulation relative thereto and setting means operable to control the relative orientation ofthe shield parts.

6. Atunnelling shield according to Claim 5, wherein the drive means and setting means are adapted and interconnected such that a drive force applied preferentially at one point on the shield's circumference is automatically accompanied by a separation ofthe shield parts at that point.

7. Atunnelling shield according to Claim 5 or claim 6, wherein the drive means comprises a plurality of circumferentially spaced hydraulic drive rams and the setting means comprises a like plurality of hydraulic setting rams respectively aligned with the drive means.

8. Atunnelling shield according to Claim 7, wherein a plurality of control valves are provided, each valve controlling supplyto one drive ram and one associated setting ram.

9. Atunnelling shield substantially as hereinbefore described with reference to and as shown in the accompanying drawings.