Performance and Cost Effectiveness of Timber Chock Construction

Eleven Australian longwall operators systematically support longwall tailgates with timber chocks. Average annual expenditure is approximately $180,000 with one operator expending over $500,000/annum on chock timber. Generally, timber chock constructions have evolved on a local and as-needed basis, resulting in a wide range of timber sizes, chock configurations and chock spacings. Given the significant and growing impact that tailgate chocks can have on safety, productivity and costs, ACARP funding of $25,000 was successfully sought to conduct research aimed at developing design and performance criteria for timber chock constructions.

A survey of longwall operators revealed that:

• At least 12 species of timber are currently used for chock constructions.
• Chock timber elements are supplied in over 10 different sizes.
• There is a variation of over 200% in timber price ex-sawmill.
• Timber price does not correlate with chock performance, with the most expensive timber having the poorest performance characteristics.
• There is a variation of over 400% in chock performance.
• Only one mining company issues a specification for chock timber and this makes little reference to Australian timber standards.
• On average, 50 manshifts are lost per annum due to injuries sustained during chock construction.

Through acting on the results of the project, the majority of mine operators that utilise timber chocks stand to achieve significant cost reductions.

The final report should be compulsory reading for any operator utilising timber chocks.