GB2236128A - Arch support system - Google Patents

Abstract

An arch support system comprises of an arch (3) including a crown section (4) and leg sections (5) (6) which are joined to invert sections (9) set into the floor of a roadway. The invert sections have a tiebar (11) joined across them. The tiebar (11) is placed in tension. The invert and the tiebar are covered with fill material to provide a floor to the roadway. <IMAGE>

Description

ARCH SUPPORT SYSTEM This invention relates to an arch support system for a roadway in a mine. The system comprises a roof arch made up of a plurality of sections including a crown section or sections and leg support sections. The roof arch support lines the profile of the arch and an invert support comprising a plurality of sections are connected to the feet of the leg support sections and covered by a floor material.

In mining and tunnelling operations it is necessary as soon as possible after a section of the mine roadway or tunnel has been cut to support the sides of the tunnel and the roof against caving.

There are a number of procedures which are well knows for doing this and one of the most common is to set against the sides of a newly cut roadway or tunnel, steel arch sections and to bolt these together to give a support to the strata. The arches are set at regular distances along the tunnel and adjacent arches are joined to each other by spacing or tiebars and often the area behind the arch is lagged either with lagging sheets or a mesh. Sometimes the whole of the inside of the tunnel arch is then lined by spraying with a suitable non-combustible material such as concrete.

In any roadway tunnel there is a natural tendency for the strata to fill in the hole which it has created. This leads to pressure being placed on the arch and in extreme conditions the arch can buckle. Quite often what happens is that the arch is able to withstand the pressure from the side of the roof and there is a phenomenon know as floor heave where the pressures on the strata cause the floor to be forced up into the passageway of the tunnel.

This causes problems where railway lines or the like are laid for transport purposes, since the distorted floor upsets the ease of passage of materials through the tunnel. In order to deal with this problem, it has previously been accepted that dinting will take place. This is where a mechanical earth moving machinery will cut away at the lifted portion of the floor and restore it to a level surface.

In order to avoid the necessity for dinting, it has also been a practice particularly when circular or near circular profiles of tunnel have been cut for the bottom of the leg sections of the arch, to be connected with further sections of an invert arch which lines the base of the tunnel. The invert sections once in position are then covered with fill to give a level surface. The use of an invert enables the arch sections to be more rigid and to prevent to a degree floor heave.

Even with the use of inverts floor heave d does s sometimes occur and this can therefore be inconvenient in the situations where the tunnel or roadway is in constant use.

It is therefore necessary to find a way whereby floor heave is reduced to a minimum and the need for dinting is removed or substantially eliminated.

According to one aspect of the present invention an arch support system for a roadway comprises a plurality of arch sections secured together and including a roof crown arch support section having leg support sections connected thereto or lining the profile of the roadway, and an invert support section - comprising a plurality of sections joined together and to the feet of the leg support sections and arranged in use to be covered by flooring material, in which a tiebar is joined across the invert at or adjacent the feet of the leg sections.

Tensioning means are preferably applied to the tiebar to ensure that in use it is permanently in tension. The tiebar itself may be a rigid rod or a flexible steel cable and the tensioning means may conveniently comprise a turnbuckle secured to the tiebar, or a ratchet winding device attached to a steel cable.

The tiebar may conveniently be connected to fixing means on the invert sections adjacent to the point where the invert sections are connected to the arch leg sections.

According to another aspect of the invention, a method of installing an arch support system as described above includes the step of driving a roadway through strata, installing a plurality of arch sections to the profile of the roadway, subsequently excavating the floor below the arch and inserting invert sections connected to the leg sections of the arch and securing a tiebar between the inverted sections adjacent to the feet of the arch and placing the tiebar in tension before infilling with material.

The method may include originally connecting a temporary foot plate to the ends of the leg sections of the arch and removing this foot plate when excavation of the floor takes place and replacing it with a connection to the invert sections.

The method may also include inserting further supports such as concrete bars between adjacent inverts to further strengthen and position the arch support section.

A yet further aspect of the invention comprises a method of setting an arch support system including driving a roadway of circular or near circular form, setting to the profile of the roadway arch sections to support the roof of the roadway and inverts to the base of the roadway, applying a tension tiebar across the invert and infilling with material to form a floor to the roadway.

In order that the invention may be readily understood one example of an arch support system in accordance therewith and using the method thereof will now be described by way of example only with reference to the four figures of the accompanying drawings.

In the drawings figure 1 shows in schematic terms a section of roadway with an arch support system in position. Figure 2 shows part of a tiebar which can be used with the invention. Figure 3 shows a detail of the connection between an invert and an arch leg section and figure 4 shows the use of a temporary foot plate.

In this example it is assumed that the tunnel which is being supported is a roadway which is being driven in a coalmine. A heading machine conventionally drives the roadway and as it advances and cuts, arches are set to support it immediately in the area of the recently exposed material.

In figure 1 of the accompanying drawings, to which reference is now made, the roadway is indicated generally as 1 in the strata 2. The profile of the roadway is lined by a D configuration arch which is shown generally at 3 and which is made up in this example of a crown section 4 and two leg sections 5 and 6 which are bolted to the crown section by fish plates (not shown). Adjacent arches 3 are joined together by tie rods 7 and the area behind the tie rods is filled in with a steel mesh lagging 8 which is then sprayed with shotcrete.

Some way behind the heading machine at a point where floor heave may have occurred the floor is excavated and an invert 9 is applied to each arch 3. The invert 9 comprises three sections which are bolted together by fish plates and which are also bolted at their ends to the ends of the leg sections 5 and 6.

A tiebar 11 is connected to the inverts adjacent to their connection with the ends of the leg sections 5 and 6 and this tiebar 11 is placed in tension.

Concrete slabs 12 are fitted between adjacent inverts and then material is placed over the slabs, invert and tiebar as backfill 13. This is then levelled off to give a floor which is some 12 inches above the tiebars 11. The result of the use of the tiebar is that the whole of the arch support system is much stronger than an equivalent arch support system without the tiebar. For example, in an arch support system where the crown arch and the leg sections are made from 6 inch by 5 inch rolled steel joists and the invert is in 8 inch by 6 inch rolled steel joists, the line load on the invert at the yield point was 9.2kN/m, the equivalent pressure on the invert was 0.184MPa and the vertical displacement of the invert centre at yield was 56.4mm.

The increase in strength on the same arch support system using a 2 inch diameter tiebar was that the line load on the invert at yield was 630kN/m, the equivalent pressure on -the invert was 1.26spa and the vertical displacement of the invert centre at yield was 4.2mn. It can thus be appreciated that the invention gives a significant improvement in strength over previous systems.

Referring now to figure 2, this shows a detail of part of a tiebar and tensioning device which can be used. The tiebar itself is shown as the rod 11 with a threaded end 14 on which a nut engages within a turnbuckle fixture 15. The turnbuckle fixture has an eye 16 for securing it to a connection on the invert 9.

In this example the threaded section 14 of the tiebar 11 is some 12 inches in length and with an arch at a 17 foot setting the tiebar is tensioned by moving the nut along the threaded section some 6 inches to place the whole of the bar il in tension. If necessary a push on cover may be placed over the turnbuckle 15.

Referring also now to figure 3, this shows in detail how the turnbuckle 15 is connected to the invert 9. A flange 17 on one section of the invert 9 has a hole which secures the eye 16 of the turnbuckle 15 with a bolt 18. Figure 3 also shows a wrap-round fishplate 19 which is used for connecting sections of the invert 9.

Figure 3 indicates the connection of the invert 9 to the arch leg section 6 via a bolt 20 and the end of the arch leg section 6 is shown as being just below the final floor level 21 and the floor level is some 12 inches above the position of the tiebar 11.

When using a method as described with reference to figure 1 the floor is excavated after the arch 3 has been set, it may be convenient to use a temporary foot plate such as at shown at 23 in figure 4. Here the arch leg section 5 or 6 will rest on the foot plate 23 when the arch 3 is originally set and the bolt 20 temporarily holds the leg section onto the foot plate 23. When excavation takes place the bolt 20 is removed so that the foot plate 23 can be taken away and replaced by the invert 9. The bolt 20 is then replaced to secure the invert to the leg section and tightened.

In an alternative method of setting the arch support system, the heading machine may not just make a D profile but make a profile which has a shallow dip in the floor so that the invert can be placed as a lining straight onto the recently excavated area at the same time as the arch 3 is set, this removes any need for the temporary foot plate 23 and the whole process of setting the arch and connecting it with tie rod 7 and concrete slabs 12 can be done as one operation before backfill 13 is put in to cover the invert and the tiebar 11.

The invert plus the tiebar will enable pressure to be withstood equivalent to circular arches given the same roadway width at floor level. The strength and cost of the system can be varied to suit the conditions by altering the spacing of the arches and this would only require a change in the mesh, tiebar and concrete block sizes.

Since the whole of the system relies on simple short components there is no problem in transporting these into a mine roadway.

Although reference has been made to a solid rod tiebar it would be appreciated that other forms of tiebar could be used such as a steel rope and this may be tensioned not by a turnbuckle but by appropriate ratchet winding devices.

Claims (15)

1. An arch support system for a roadway, the system comprising a plurality of arch sections severed together and including a roof crown arch support section and leg sections connected thereto for lining the profile of the roadway, and an invert support section comprising a plurality of sections joined together and to the feet of the leg support sections and arranged in use to be covered by flooring material, in which a tiebar is joined across the invert at or adjacent the feet of the leg sections.

2. The system as claimed in claim 1 and including tensioning means for the tiebar.

3. A system as claimed in claim 2 in which the tensioning means comprises a turnbuckle.

4. A system as claimed in claim 2 in which the tensioning means comprises a ratchet mechanism.

5. A system as claimed in any preceding claim in which the tiebar is connected to a coupling member on the invert section.

6. A system as claimed in any preceding claim wherein the tiebar is a rod.

7. A system as claimed in any one of claims 1 to 5 in which the tiebar is a steel rope.

8. A system as claimed in any preceding claim and including concrete bars spanning the distance between adjacent inverts.

9. A system as claimed in any preceding claim and including a temporary foot plate connected to the end of a leg section prior to its connection to the invert.

10. An arch support system as claimed in any preceding claim substantially as hereinbefore described with reference to the accompanying drawings.

11. A method of setting an arch support system as claimed in any preceding claim in a roadway, including the steps of driving the roadway, installing the arch section to the profile of the roadway, subsequently excavating the floor of the roadway, connecting sections of an invert to the ends of leg sections of the arch, connecting a tiebar across the invert, tensioning the tiebar and backfilling to cover the invert and the tiebar and to provide a floor to the roadway.

12. A method as claimed in claim 11 and including securing a temporary foot plate to the leg sections of the arch section, removing the foot plate to enable the invert to be connected to the leg sections and securing the invert to the leg sections.

13. A method as claimed in claim 11 or claim 12 and including the steps of placing lagging material between adjacent inverts of arch support sections.

14. A method of setting an arch support system as claimed in any one of claims 1 to 10 including the step of excavating a roadway to a circular or generally circular cross-section, setting roof and leg sections to the roof and side of the roadway, securing an invert section to the end of the leg sections, securing a tiebar across the invert section and placing the tiebar in tension and subsequently covering the invert and the tiebar with backfill material.

15. A method of setting an arch support system of the kind as claimed in any one of claims 1 to 10 and substantially as hereinbefore described.