GB2214950A

GB2214950A - Mine chockpieces of timber

Info

Publication number: GB2214950A
Application number: GB8821755A
Authority: GB
Inventors: John Douglas Thompson
Original assignee: Individual
Current assignee: Individual
Priority date: 1988-02-02
Filing date: 1988-09-16
Publication date: 1989-09-13
Anticipated expiration: 2008-09-16
Also published as: GB8802302D0; GB2214950B; GB8821755D0

Abstract

A mine chockpiece for use in strata control comprises a single rectangular longitudinal web plate 10 of timber, having at each end thereof a rectangular timber end plate 11 disposed normal to the web plate 10 in abutment with the end faces of the web plate 10, and rectangular timber, side blocks 12 abutting the inside face of the end plate 11 and the adjacent faces on opposite sides of the web plate 10, the top and bottom sides of the chockpiece may have rectangular timber cover plates 13. The chockpiece components are mutually secured by nailing. The chockpiece is capable of economic manufacture from relatively cheap timber. Different useful load/yield characteristics are obtained depending upon the grain directions of the end plates and the side blocks. <IMAGE>

Description

CHOCK PIECES FOR STRATA CONTROL IN MINES This invention relates to mine chocks, and to chockpieces for use in constructing mine chocks.

Conventional timber mine chocks used in strata control underground consist of a plurality of solid timber pieces (chockpieces) of generally square crosssection arranged with the timber grain generally horizontal in a stack configuration defining at least four supporting columns at the points of overlapping intersection of the chockpieces. Such a configuration is achieved by using two chockpieces in each layer of the stack. A stack having three chockpieces in each layer provides nine supporting columns.

Timber shortages have caused attempts to be made to construct mine chocks from other materials and some success has been achieved using cellular concrete products incorporating wire cages or frames. Nevertheless, many operatives concerned in the industry still prefer the traditional timber products, not only for their particular suitability in terms of load/yield characteristic, but also because the timber products are less prone to damage during transit and handling and are less harsh on operatives in the handling of the chockpieces.

Accordingly, there is currently a potential market for mine chockpieces which possess some of the favoured properties of conventional timber products and which can be produced economically.

Advances in geological studies have brought a greater understanding of certain aspects of strata control in mining, resulting in a possibility of specifying more accurately than hitherto what would be the ideal load/yield characteristic of a mine chock in any given location. Accordingly, the same potential market as above mentioned exists for mine chockpieces and a system of mine chock construction whereby a desired load/yield characteristic of a mine chock can be more closely achieved than hitherto.

Proposals described in UK Patent Specification No 2160914 envisage mine chockpieces fabricated from timber components mutually secured by means of an adhesive and/ or by externally applied bands. Although these previous proposals demonstrated that certain configurations of such fabricated chockpieces could perform at least as well as conventional chockpieces, it was found that the sum of material and manufacturing costs for these fabricated chockpieces was still too high to displace conventional chockpieces.

An object of the present invention is to provide a mine chockpiece for mine chock construction for the potential market as outlined above and more economically than hitherto.

According to the present invention, there is provided a mine chockpiece comprising a single rectangular longitudinal web plate of timber having at each end thereof a rectangular timber end plate disposed normal to the web plate in abutment with the end face of the web plate, and rectangular side blocks abutting the inside face of the end plate and the adjacent faces on opposite sides of the web plate.

Further, according to the present invention, there is provided a mine chock comprising a plurality of chockpieces each as aforesaid and arranged to define supporting columns and with the general planes of the web plates arranged upright.

Embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Fig. 1 is a perspective view of part of a fabricated chockpiece in accordance with the present invention; Fig. 2A is a sectional plan view on the line lIA-lIA in Fig. 1; Fig. 2B is a sectional end view on the line IIB-IIB in Fig. 1; and Figs. 3 to 10 inclusive are graphical representations of load/yield characteristics for various different mine chock constructions all in accordance with the present invention.

In Figs. 1, 2A and 2B of the drawings, one end only of the mine chockpiece is shown the other end being of identical construction. The chockpiece consists of a single rectangular longitudinal central web plate 10 having its general plane arranged upright, end plates 11 each of rectangular configuration and diposed symetrically normal to the web plate 10 in abutment with the respective end faces of the web plate 10, rectangular side blocks 12 arranged symetrically in abutment with the inside face of each end plate 11 and the adjacent upright faces of the web plate 10, and cover plates 13 each of rectangular configuration and abutting the respective narrower side of the web plate 10 and covering the co-planar faces of the end plates 11 and side blocks 12.In Fig. 1, the uppermost cover plate 13 is shown in chain dotted outline in order to reveal the arrangement of the components thereunder.

The side blocks 12 are secured to the web plate 10 by means of metal nails 14, and the end plates 11 are secured to the web/side block assemblies by means of metal nails 15 which are oppositely-skewed to lock the construction. The cover plates 13 are similarly fixed by means of metal nails 16.

The total longitudinal dimension of the chockpiece is 900mm, and the cross-sectional outline dimensions are 150mm by 150mm. The web plate 10, the end plates 11 and the side blocks 12 are of common thickness 50mm, and the cover plates 13 are each 12.5mm thick. The crosssectional outline of the support column-forming end portion of the chockpiece measures 150mm by 150mm.

Accordingly, each support block 12 has a width dimension (in the longitudinal direction of the chockpiece) of 100mm.

All of'the timber components of the chockpiece are of spruce.

The grain direction of the web plate 10 and of the cover plates 13 is always parallel with the longitudinal dimension thereof. However, the load/yield characteristic of the chockpiece is dependent upon the grain directions of the end plates 11 and side blocks 12.

In a modification of the chockpiece described above, the cover plates 13 are omitted entirely. In a further modification, the cover plates 13 are replaced by smaller cover plates which cover only the support column-forming portions of the chockpieces.

In a further modification, the web plate is disposed offset with respect to the longitudinal centre line of the chockpiece, and single or relatively narrow side blocks are provided on one side of the web plate whilst double or relatively wide side blocks are provided on the other side.

The following examples illustrate the general load/yield characteristics attainable in mine chocks constructed using chock pieces in accordance with the present invention. In each case, a test chock was constructed using the chockpieces with the web plates upright.

Example 1 In this example, the chockpieces had no cover plates, and both the end plates and the side blocks were arranged with their grain directions upright. The load/yield characteristic peaked at 64 tonnes generally as illustrated in Fig. 3.

Example 2 In this example, the chockpieces had no cover plates, and the grain direction for both the end plates and the side blocks was horizontal. The load/yield characteristic peaked at 17 tonnes, generally as illustrated in Fig. 4.

Example 3 In this example, each of the chockpieces had two full length cover plates (as shown in Fig. 1), and the grain direction for the end plates and for the side blocks was horizontal. The load/yield characteristic peaked at 18 tonnes, generally as illustrated in Fig. 5.

Example 4 In this example, each of the chockpieces had two fulllength cover plates, and the grain direction for the end plates was horizontal and for the side blocks was upright. The load/yield characteristic peaked at 33 tonnes, generally as illustrated in Fig. 6.

Example 5 In this example, each chockpiece had two full-length cover plates, and the grain directon for each side block was horizontal and for each end plate was upright.

The load/yield characteristic peaked at 36 tonnes, generally as shown in Fig. 7.

Example 6 In this example, each chockpiece had two full-length cover plates, and the grain direction for both the side blocks and the end plates was upright. The load/yield characteristic peaked at 77 tonnes, generally as shown in Fig. 8.

Example 7 In this example, each chockpiece had four small cover plates, and the grain direction for both the side blocks and the end plates was upright. The load/yield characteristic peaked at 97 tonnes, generally as shown in Fig. 9.

Example 8 In this example, each chockpiece had four small cover plates, and the grain direction for both the side blocks and the end plates was horizontal. The load/yield characteristic peaked at 55 tonnes, generally as shown in Fig. 10.

The load/yield characteristics for the various configurations of chockpiece in the foregoing examples fall generally into two categories, namely a first category in which a distinct "peak" is present, and a second category in which the load value is generally sustained for a relatively longer period of yield.

The former category of load/yield characteristic is of particular value in connection with mine chocks placed as wwastebreakers." The second category of load/yield characteristic has a more general application for roof support.

Claims

1. A mine chockpiece comprising a single rectangular longitudinal web plate of timber having at each end thereof a rectangular timber end plate disposed normal to the web plate in abutment with the end face of the web plate, and rectangular side blocks abutting the inside face of the end plate and the adjacent faces on opposite sides of the web plate.

2. A mine chockpiece according to claim 1, wherein the web plate is disposed on the longitudinal centreline of the chockpiece.

3. A mine chockpiece according to claim 1 or 2, wherein the said web plate and each end plate and each side block are of common thickness.

4. A mine chockpiece according to any one of the preceding claims, wherein the web plate and the end plates and the side blocks are mutually secured by means of nails.

5. A mine chockpiece according to any one of the preceding claims, wherein the end plates are of square configuration.

6. A mine chockpiece according to any one of the preceding claims, wherein the grain direction of the web plate is generally parallel with the longitudinal dimension thereof, the end plates have a mutually common first grain direction, and the side blocks have a mutually -common second grain direction, the first and second grain directions being generally mutually parallel or mutually normal.

7. A mine chockpiece according to any one of the preceding claims wherein the chockpiece comprises rectangular timber cover plates abutting each narrower side face of the web plate and covering the co-planar faces of the end plates and the side blocks.

8. A mine chockpiece according to claim 7, wherein the chockpiece comprises two said cover plates each of longitudinal dimension equal to that of the chockpiece.

9. A mine chockpiece substantially as hereinbefore described with reference to and as shown in Figs. 1, 2A and 2B of the accompanying drawings.

10. A mine chock comprising a plurality of chockpieces each as claimed in any of the preceding claims and arranged to define supporting columns and with the general planes of the web plates arranged upright.