GB2149833A

GB2149833A - Cast concrete segments and assemblies comprising such segments

Info

Publication number: GB2149833A
Application number: GB08330764A
Authority: GB
Inventors: Charles Geoffrey Smith
Original assignee: Coal Industry Patents Ltd
Current assignee: Coal Industry Patents Ltd
Priority date: 1983-11-18
Filing date: 1983-11-18
Publication date: 1985-06-19
Also published as: GB8330764D0; GB2149833B

Abstract

A cast concrete segment (1) for use in an assembly of segments in which joint end faces (12) of the segments abut neighbour components (14), comprises a cast concrete body (10) and pre-cast glassfibre reinforced cement end portions (11) defining the faces (12). <IMAGE>

Description

SPECIFICATION Cast concrete segments and assemblies comprising such segments This invention relates to cast concrete segments and assemblies comprising such segments.

In particular, although not exclusively, the present invention relates to cast concrete segments for installation in an underground roadway or tunnel.

It is known for a plurality of arcuate cast concrete segments to be arranged end to end to form a generally annular assembly around the newly exposed inner boundary wall of a circular roadway or tunnel. As the working face of the roadway or tunnel is excavated to extend the roadway or tunnel further, annular assemblies are erected to provide a substantially continuous lining along the inner boundary wall.

Although the cast concrete segments may include internal steel reinforcement, the concrete adjacent the outer faces of the segments tend to have little tensile strength. Consequently, it is common in underground mining installations to introduce compressible packing material between the joint faces of adjacent segments. The compressible material may comprise, for example, wood or chipboard.

Unfortunately, it is frequently found when the packing material is squeezed during initial convergence of the rock strata adjacent the roadway or tunnel cracking occurs across the joints between segments. The purpose of the compressible packing is to allow initial convergence thereby tending to reduce the final loading on the concrete. Unfortunately, as the packing is squeezed during convergence of the rock strata a tensile force is induced across the concrete faces at the joints leading to cracking.

An object of the present invention is to provide an improved cast concrete segment which tends to overcome or reduce the above mentioned cracking problem.

Accordingly the present invention provides a cast concrete segment for use in an assembly of segments in which joint end surfaces of the segments abut neighbouring components, the segment having a body cast concrete and reinforced joint end portions defining faces adapted to abut neighbouring components in the assembly.

Preferably, each reinforced joint portion comprises a precast reinforced layer.

Advantageously, the pre-cast reinforced layer comprises glass fibre reinforced cement.

Preferably, the layer of glass fibre reinforced cement has a relatively smooth outward facing surface for abutment with a neighbouring component and a relatively rough inward facing surface directed towards the cast concrete body.

Conveniently, the layer of pre-cast glassfibre reinforced cement is between five and ten millimeters in thickness.

Advantageously, the cast concrete body is provided with reinforcements in the form of a steel framework or rods.

The present invention also provides an annular assembly of cast concrete segments, joint end faces of the segments abutting neighbouring components, each segment having a generally arcuate body of cast concrete and reinforced joint end portions defining faces adapted to abut neighbouring components in the assembly.

Preferably, each reinforced joint portion comprises a pre-cast reinforced layer.

Advantageously, the pre-cast reinforced layer comprises glassfibre reinforced cement.

Preferably, the layer of glassfibre reinforced cement has a relatively smooth outward facing surface for abutment with a neighbouring component and a relatively rough inward facing surface directed towards the cast concrete body.

Conveniently, the layer of pre-cast glassfibre reinforced cement has a thickness of between five and ten millimeters.

Advantageously, at least some of the cast concrete segments are provided with reinforcement extending throughout the body in the form of steel frameworks or rods.

Preferably, the neighbouring components for abutment by the joint faces comprise pads of compressible material.

By way of example, one embodiment of the present invention will be described with reference to the accompanying drawings, in which: Figure 1 is an incomplete cross-section of an underground mine roadway lined with annular assemblies of cast concrete segments; Figure 2 is a side elevation of a cast concrete segment shown on an enlarged scale to Fig. 1; Figure 3 is an end view of the segment of Fig. 2; and Figure 4 is a scrap view on an enlarged scale illustrating a joint between two segments in the annular assembly.

Fig. 1 shows an incomplete cross-sectional view of a circular roadway in an underground mine, the inner boundary wall of the roadway being lined with annular assemblies of cast concrete segments 1. In the embodiment shown in Fig. 1 each annular assembly comprises twelve segments.

As rock or mineral is excavated from the working face to advance the roadway the annular assemblies are erected around the newly exposed rock or mineral face to retain the face. Upon a new assembly being erected a grout filling 2, for example, pea gravel, is injected behind the erected assembly to fill the cavity between the assembly and the rock or mineral face. The lower portion 3 of the lined roadway is filled with ballast or consolidated backfill material to provide a stable and even road-way floor 4. As indicated in Fig. 1 the roadway contains a belt conveyor structure 5 for transporting material excavated from the working face and a rail track installation 6 for carrying men and supplies along the roadway.

Figs. 2 and 3 show cast concrete segment 1 in more detail. Each segment 1 comprises a cast concrete body 10 of generally arcuate form (as seen in Figs. 1 and 3). The body may be provided with reinforcement in the form of a steel framework or rods. In other embodiments no steel reinforcement is provided.

Each radially extending end of the segment ie a joint end which lies adjacent a similar joint end of a neighbouring segment in an annular assembly, is provided with a layer 11 of pre-cast glassfibre reinforced cement. Typically the layer has a thickness of between five and ten millimeters. As seen in Fig. 4 which shows adjacent joint end of two neighbouring segments in an annular assembly each layer of pre-cast glassfibre reinforced cement is arranged with a smooth surface 1 2 facing outwards from the associated segment. The relatively rough surface 1 3 of the layer 11 faces inwards to assist adhesion of the layer to the body of the segment during casting of the segment.

As seen in Fig. 1 and 4 a pad 14 of compressible packing material for example wood or chipboard is inserted between to adjacent joint ends.

Means (not shown) are provided for enabling the segment to be connected to lifting equipment during erection. Also means (not shown) are provided for connecting adjacent segments together upon erection and for introducing grout behind the assembly.

In use, once the annular assembly is erected and the grout filling is set, convergence of the adjacent rock strata causes each pad of packing material to be squeezed and tensile forces are induced across the joint faces of the segments. However, the glassfibre reinforced cement layer enables the segments to withstand the induced tensile forces without cracking occurring or with greatly reduced cracking compared to prior known segment.

Hence segments constructed in accordance with the present invention tend to increase the working life of the cast concrete segments used in underground mines.

Claims

1. A cast concrete segment for use in an assembly of segments in which joint end surfaces of the segments abut neighbouring components, the segment having a body of cast concrete and reinforced joint end portions defining faces adapted to abut neighbouring components in the assembly.

2. A segment as claimed in claim 1, in which each reinforced joint portion comprises a pre-cast reinforced layer.

3. A segment as claimed in claim 2, in which the pre-cast reinforced layer comprises glassfibre reinforced cement.

4. A segment as claimed in claim 3, in which the layer of glassfibre reinforced cement has a relatively smooth outward facing surface for abutment with a neighbouring component and a relatively rough inward facing surface directed towards the cast concrete body.

5. A segment as claimed in claim 2, 3 or 4, in which the thickness of the layer is between five and ten millimeters.

6. A segment as claimed in any one of the preceding claims, in which the cast concrete body is provided with reinforcement in the form of a steel framework or rods.

7. An annular assembly of cast concrete segments, joint end faces of the segments abutting neighbouring components, each segment having a generally arcuate body of cast concrete and reinforced joint end portions defining faces adapted to abut neighbouring components in the assembly.

8. An assembly as claimed in claim 7, in which each reinforced joint portion comprises a pre-cast reinforced layer.

9. An assembly as claimed in claim 8, in which the pre-cast reinforced layer comprises glassfibre reinforced cement.

10. An assembly as claimed in claim 9, in which the layer of glassfibre reinforced cement has a relatively smooth outward facing surface for abutment with a neighbouring component and a relatively rough inward facing surface directed towards the cast concrete body.

11. An assembly as claimed in claim 8, 9 or 10, in which the thickness of the layer is between five and ten millimeters.

1 2. An assembly as claimed in any one of the preceding claims 7 to 11, in which at least some of the segments are provided with reinforcement substantially extending throughout the body, the reinforcement being in the form of a steel frame work or rods.

1 3. An assembly as claimed in any one of the preceding claims 7 to 12, in which the neighbouring components for abutment by the joint faces comprise pads or compressible material.

14. A cast concrete segment substantially as described herein and substantially as shown in the drawings.

1 5. An annular assembly substantially as described herein with reference to the accompanying drawings.