GB2114183A

GB2114183A - Adjustable support element

Info

Publication number: GB2114183A
Application number: GB08201434A
Authority: GB
Inventors: Gordon Bertram Dawson
Original assignee: Barker And Co Ltd R E
Current assignee: Barker And Co Ltd R E
Priority date: 1982-01-19
Filing date: 1982-01-19
Publication date: 1983-08-17

Abstract

An adjustable support element particularly for use in adjusting the height of underground roadway supports, which comprises a hollow tubular housing 3 which may be rectangular closed at one end with a piston head 4 slidable in it and a liquid entry port 6. According to a method of adjusting a support girder 1 the support element is positioned between the girder 1 and a surface and a settable liquid 7 pumped into it through the liquid entry port 6 so as to put a pre-load on the girder. The liquid then sets to a rigid mass which supports the girder in position. A chemical accelerator may be introduced into the housing prior to pumping the settable liquid so as to reduce the time for the liquid to set. <IMAGE>

Description

SPECIFICATION Adjustable support element The present invention relates to an adjustable support element and to a method of adjusting a support girder therewith.

In deep underground workings such as coal mines road-way tunnels are provided for the passage of men and materials as well as for ventilation purposes. These roadways are generally supported by steel arches at regular intervals along them with a convering between the arches to make the roadway safe and stable.

To be fully effective the arches must be in contact with the roadway roof and normally they are forced up against the roof at a certain preset pressure known as the pre-load.

When cutting the roadway tunnels it is not possible to make them an accurate size and so the tunnels are cut larger than the arches, the base of each support girder of the arch being adjusted after the arch is in position to give the required pre-load. This adjustment is conventionally provided by knocking wedges in between the bottom of the support girder and the floor of the roadway but this does not give an accurate pre-load and is unstable if the amount of adjustment required is large. A more controlled method is to use hydraulic jacks as adjustable support elements but these are expensive and are wasteful in situations where, once set, a support element is not tobe moved again, as in roadway tunnels.

According to one aspect of the present invention we provide a method of adjusting a support girder in which a support element having a hollow tubular housing closed at one end and a piston slidable axially within the housing is positioned between a surface and one end of the support girder with its axis parallel to the support girder, and wherein a liquid capable of setting to a rigid mass is introduced into the space between the piston and the housing under pressure whereby to adjust the support girder and to support it when the liquid solidifies.

This method gives control over the pre-load, as with the use of hydraulic jacks but allow much simpler and cheaper support elements to be used since once set the rigid mass provides the permanent support.

Preferably, a chemical accelerator capable of increasing the speed of setting of the liquid is mixed with the liquid when it is introduced into the space between the piston and the housing.

According to a second aspect of the present invention we provide an adjustable support element comprising a hollow tubular housing of polygonal cross-section closed at one end, a piston slidable axially within the housing and a liquid entry port in the wall of the housing adjacent the closed end.

The polygonal tubular support element is simpler to manufacture than the accurately machined cylinders required for hydraulic jacks.

Preferably, the housing is of rectangular crosssection, which allows it to fit closely around the leg of an H-section support girder.

An adjustable support element and method of adjusting a support girder according to the present invention will now be described by way of example and with reference to the accompanying drawings in which: Figure 1 shows an arched roadway support incorporating adjustable support elements according to the present invention; Figure 2 is an enlarged section taken on the line Il-Il in Figure 1; and Figure 3 shows an enlarged sectional elevation of part of Figure 1.

Referring to Figures 1 and 2, an arched roadway support for use in underground workings such as coal mines comprises two or more lengths of curved H-section steel girders bolted together to form an arch 1. The top of the arch fits snugly against the roof of the roadway and its legs are each supported by an adjustable support element 2.

Each support element 2, as seen in Figure 3, consists of a hollow steel tube 3 of rectangular section in which the bottom part of the corresponding arch leg can fit. The tube is closed at the bottom and has a piston head 4 which carries the lower end of the arch leg. This piston head is generally planar with a flexible rim 5 inclined downwards towards the bottom of the tube and engageable with the inner wall of the tube so as to form a sliding seal. The central paft of the piston head 4 may be reinforced with a rigid plate (not shown in Figure 3).

At the lower end of the tube 3 is a liquid entry port 6 having a non-return valve and being connectable to a supply pipe from a source of liquid cementaceous grout.

In use the arch 1, which is shorter than the height of the roadway roof, is assembled in position with each leg resting on the piston head 4 of the support element placed between the arch and the floor of the roadway. A cementaceous grout 7 is then pumped into each support element through the liquid entry ports 6, which forces each piston head 4 upwards until the arch engages the roadway roof. Pumping is continued to establish a predetermined pressure (pre-load) on the support girders of the arch and the supply pipes then disconnected, the pressure being held by the non-return valve and sliding seal.

Once the group 7 has set it will support the support girders of the arch and also maintain the pre-load without relying on the strength of the tube 3 or the sliding seal. Thus relatively inexpensive tube and piston constructions can be used which need only withstand the pressure of the pre-load for the time the grout 7 takes to set.

In particular, a tube of polygonal cross-section can be used which is simply manufactured from sheet metal.

This makes the present invention cheaper and simpler than using hydraulic jacks with their accurately machine cylinders which must be strong enough to withstand excess pressures such as can occur with strata movements and whose seals must last for the lifetime of the support. However, it is necessary that the grout sets as rapidly as possible since the full strength of the support element is not available until the grout has set. For this purpose a chemical accelerator may be placed inside the tube 3 which causes rapid setting of the grout without the danger of grout solidifying in the support pipes or pumping apparatus.

The method of the present invention is particularly suitable for use with the yieldable support elements described in the copending U.K.

patent application, 80 1 5910 filed on 13th May, 1 980. These have a tubular housing with a block of compressively material in it carrying a support girder. By inserting a suitab!e piston head in the housing between the closed bottom end and the block, and a liquid inlet port at the lower end of the housing, a settable liquid can be introduced below the block of compressible material to adjust the support girder in the manner of the present invention.

While the adjustable support element has been described for use with arched roadway supports, it can be used with any type of support where support girder needs to be adjusted.

Claims

1. A method of adjusting a support girder in which a support element having a hollow tubular housing closed at one end and a piston slideable axially within the housing, is positioned between a surface and one end of the support girder with its axis parallel to the support girder, and wherein a liquid capable of setting to a rigid mass is introduced into the space between the piston and the housing under pressure whereby to adjust the support girder and to support it when the liquid solidifies.

2. A method according to claim 1, wherein the settable liquid is cementaceous grout.

3. A method according to claim 1 or claim 2, wherein a chemical accelerator capable of increasing the speed of setting of the liquid is mixed with the liquid when it is introduced into the space between the piston and the housing.

4. An adjustable support element comprising a hollow tubular housing of polygonal cross-section closed at one end, a piston slidable axially within the housing and a liquid entry port in the wall of the housing adjacent the closed end.

5. A support element according to claim 4, wherein the housing is of rectangular crosssection.

6. A support element according to claim 4 or claim 5, wherein the liquid entry port contains a non-return valve.

7. A support element according to any one of claims 4 to 6, wherein the piston head has flexible edges lying against the walls of the housing and directed towards the closed end of the housing.

8. A support element according to any one of claims 4 to 7, wherein the housing contains a chemical accelerator capable of increasing the speed of setting of a settable liquid when the liquid is introduced into the space between the piston and the housing.

9. An adjustable support element substantially as herein described with reference to and as illustrated by the accompanying drawings.

10. A method of adjusting a support girder substantially as herein described with reference to and as illustrated by the accompanying drawings.