GB2132249A - Tunnel linings - Google Patents

Abstract

A tunnel lining having a smooth inner surface is assembled from lining segments 1 having recesses on their inside surface between inwardly extending ribs and pre-formed blocks 7 fitted within recesses and held in place by threaded bolts 10 passing through the blocks 7 and engaging threaded inserts 8 provided in the segments 1. <IMAGE>

Description

SPECIFICATION Tunnel linings This invention relates to a method of lining tunnels of the kind comprising part-circular preformed sections secured together; some or all of the sections having ribs defining similar recesses on their inner faces.

Underground tunnels are generally fabricated from pre-formed part-circular sections of reinforced concrete. The reinforced concrete sections are generally formed with recesses on their inner faces leaving an outer skin and internal circumferentially and axially extending ribs. This arrangement provides adequate strength and also saves material but in addition the ribs are generally formed with apertures or slits for engagement by bolts for securing the sections to one another.

If it is desired that the finished tunnel should present a smooth inner surface, for example for the flow of water or sewage, it has hitherto been customary to cast an inner skin around the interior of the tunnel. The inner skin is formed by erecting an internal framework suitably spaced from the sections and packing concrete into the space between the sections and the framework by hand.

Such a method is very time consuming and inefficient since oniy a short axial length of tunnel can be dealt with at one time and while waiting for the concrete to set further work beyond that section of the tunnel may be inhibited.

British Patent Specification 1160111 describes a method of making a smooth inner surface in which the recesses are filled with pre-formed blocks. The blocks are of a size and shape to be an easy fit within the recesses in the segments with the inner surfaces of the blocks following the curvature of the tunnel and being substantially continuous with the inner surfaces of the ribs.

The blocks are secured within the recesses by a fairly thick layer of a resin bonded adhesive or by cement grout. In order to hold the blocks in place while the adhesive or the grout sets, a ring is disposed within the tunnel. The ring is of smaller diameter than the innermost curvature of the sections and wedges are disposed between the ring and each block to hold the latter securely in place.

It has been found that the ring disposed within the tunnel is cumbersome, its positioning is time consuming and use of the ring may interfere with the other operations in the tunnel.

According to one aspect of the present invention there is provided a method of lining tunnels in which the tunnel lining is built up from curved pre-formed segments some or all of which have recesses on their inside surfaces between inwardly extending ribs and pre-formed blocks of a size and shape to fit within the recesses with the inner surfaces of the blocks following the curvature of the tunnel and substantially continuous with the inner surfaces of the ribs are fitted into the recesses and secured in the recesses by threaded bolts passing through the blocks and engaging threaded inserts cast into the segments.

This method of securing the blocks requires no external support for the blocks whatever and allows the normal progress of the tunnel to proceed unhindered.

An advantage is also gained when fixing large blocks, in greatly reducing the fixing time for each block, as there is no need to wait for the adhesive or mortar to set.

The blocks may be cast in concrete or of other material suitable for use in a tunnel lining. Each block may be provided with one or more bolts engaging corresponding inserts, the number of bolts required varying according to the size and shape of the blocks. The blocks may be provided with interior recesses to accommodate the heads of bolts or other connecting means joining the segments together to form the tunnel lining.

A method of lining a tunnel according to one embodiment of the invention will now be described by way of exampie with reference to the accompanying drawings in which: Figure 1 shows a transverse section through an annulus of a tunnel lining formed of segments having internal recesses, Figure 2 shows a section through a recess in a segment similar to those in Figure 1 having a block installed therein, Figure 3 is a section of the block of Figure 2 perpendicular thereto, Figure 4 is a base view of the block of Figure 3, Figure 5 is a section along V-V of Figure 4.

As shown in Figure 1, a number of similar arcuate tunnel segments 1 are joined end-to-end to form an annulus for a tunnel lining. The segments are formed of reinforced concrete and are of generally rectangular shape. The inner surfaces of the segments have a number of symmetrically arranged recesses 2 which are generally rectangular in shape and are separated by inwardly projecting ribs 3. The ribs abutting an adjacent segment of the annulus are provided with recesses 4 and holes 5 to receive bolts holding the segments together to form the annulus. Similar ribs are provided at the side edges of the segments and these ribs have recesses, similar to recesses 4, and holes 6 to enabie successive annuli to be bolted together side-by-side to provide a continuous tunnel lining.

As shown in Figure 1, the side walls of the recesses 2 formed by the ribs are inclined inwardly.

After assembly together of the segments the recesses 2 are filled with blocks 7 to form together with ribs 3 a substantially smooth inner surface of the tunnel lining. The blocks are shaped to fit the interior of the recesses closely and are cast from a cement/aggregate mixture, such as a cement/fly ash mixture.

In order to secure the blocks in the recesses the bottoms of the recesses are provided with screwthreaded inserts 8 cast into the segment, as shown in Figure 2, and the blocks are provided with holes 9 corresponding to the inserts to receive a threaded bolt 10 entering the insert to clamp the block in place. The exposed surface of the insert is provided with a recess 11 to accommodate the head of the bolt and after clamping of the block in place this recess may be filled with cement to protect the bolt head from corrosion and render the inner surface of the tunnel lining smooth.

More than one bolt and corresponding insert may be provided for each block, according to the dimensions of the block and recess. The block shown in Figures 2 to 5 receives two bolts in holes 9 spaced in the longitudinal direction of the tunnel. This block also has end recesses 12 intended to accommodate the heads of bolts, such as bolts 6 in Figure 1, clamping adjacent annuli together.

It will be appreciated that installation of the blocks to form a continuous inner surface for the lining is easy and rapid. As no adhesive or grout is required to hold the blocks in place there is no need for any means, other than the bolts 10, to be used for holding the blocks in place during installation so that mounting of the blocks will not interfere with other operations in the tunnel.

Claims (6)

1. A method of lining tunnels in which the tunnel lining comprises pre-formed segments at least some of which have a recess on their inside surface between inwardly extending ribs and pre-formed blocks of a size and shape to fit within the recesses are fitted into the recesses and secured therein by threaded bolts passing through the blocks and engaging threaded inserts cast into the segments, the inner surfaces of the blocks being substantially continuous with the inner surfaces of the ribs and forming a substantially smooth inner surface of the tunnel lining.

2. A method according to claim 1, in which the blocks are formed of cement or a cement/ aggregate mixture.

3. A method according to claim 2, in which the blocks are formed of a cement/fly ash mixture.

4. A method according to any preceding claim, in which the blocks are provided with interior recesses to accommodate connecting means joining the segments together.

5. A method according to claim 4, in which the recesses are filled with cement after the blocks are fitted into the recesses.

6. A method of lining tunnels, substantially as hereinbefore described with reference to the accompanying drawings.