Cost Effective Use of PUR and Optimising Large-Scale Injected Strata Reinforcement

The project arose from a recognition that both small-scale and large-scale injected strata reinforcement techniques have the potential to play significant roles within the coal mining industry where the preferred support methods such as tendons, standing support and face powered supports are unable to exert adequate ground control.

The past use of large-scale injected strata reinforcement techniques to consolidate fault zones ahead of longwall faces has not always produced the intended benefits, despite considerable expenditure and the involvement of significant amounts of time and effort. It has been difficult to establish the need for such measures and assess their success.

In the civil engineering industry, grouting operations, in their many forms, are applied in a controlled and closely monitored manner following extensive site investigations and a rigorous design process. Such an approach is generally absent in the mining industry. This project aims to provide a firm foundation for rectifying this situation by presenting information from the civil engineering industry that represents the current state-of-the-art with regard to grouting and by considering the applicability of this information to coal mines. It is important to bear in mind that grouting is a young field of engineering that is evolving rapidly and that for coal mining to make best use of grouting it will be necessary to keep abreast of new developments.

The injection of polyurethane (PUR) in situations where the roof of a roadway has undergone considerable displacement and is highly fractured has frequently resulted in successful outcomes. However, the contribution that PUR played in stabilising the roof in these situations and the mode of action of the PUR are often not clear. Given the cost of PUR and the fact that it is commonly applied in situations where there are severe time constraints and restrictions on the quantities of PUR that may be injected, a better understanding of the reinforcement action of PUR will assist in designing PUR operations.

The overall objective of the project is to conduct a range of trials to investigate various aspects of strata consolidation and ultimately produce guidelines in the form of a single 'handbook-style' reference covering the range of strata consolidation techniques utilised in collieries. This would make available for the first time to Australian coal producers, methodologies for the rational application of these materials and techniques.

As the title suggests, the research project may readily be separated into two distinct research elements:

• Cost Effective Use of PUR.
• Optimising Large-Scale Injected Strata Reinforcement.

In view of the clear differences in the two elements of the project, each element will be dealt with entirely separately, the PUR element of the report will be found in Element A, the large-scale injected strata reinforcement will be found in Element B. Although there may be a degree of overlap in some respects, most users will only be interested in one element at a time according to their circumstances and, therefore, it is preferable for ease of reference that each element be fully self-contained. For both elements, The aim is to produce a user-friendly report that is of direct practical benefit to mines.

The PUR element includes numerous case studies which illustrate the manner in which PUR is being applied within the coal mining industry. These are analysed in order to develop a clearer understanding of the manner in which PUR exerts a stabilising influence on highly fractured roofs and, in the lighter of this, to consider how to apply PUR in a more effective and efficient way.

Element B is chiefly concerned with assessing the current situation with respect to large-scale injected strata reinforcement in the coal mining industry and the extent to which industry practice from the civil engineering industry is applicable to coal mines Consequently, a significant proportion of the report concentrates on relevant state-of-the-art knowledge from the civil engineering industry on matters such as material properties, equipment selection, contract management, quality control and assessment, and considering the relevance of this knowledge within a coal mining context.