Geomechanical design of cemented paste backfill systems (phase III)

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Underground mining creates large voids which must be backfilled to support the surrounding rockmass and limit the potential for violent rockbursts and large ground movements. An increasingly popular form of backfilling is Cemented Paste Backfill (CPB), which can be delivered relatively quickly and so accelerates the rate of mining, thereby enhancing the Net Present Value of the mineral reserve. It also re-uses tailings which would otherwise typically be pumped to a surface tailings pond, and so has positive environmental impacts. Much has been done in the last two decades to increase the effectiveness and efficiency of CPB systems. There are however a few design challenges left that, if addressed, can dramatically improve CPB's impact on mining operations. Improved structural analyses are required to safely design and construct the barricades that hold back CPB from the rest of the mine workings. Better predictions of how fast the CPB transitions from "slurry" to "solid" are needed so that the mine can resume production blasting near the backfill as quickly as possible. And an improved understanding of how CPB can be self-supporting when undermined is needed so that more effective mine planning strategies can be adopted.The proposed work is a continuation of an ongoing multi-year, industry funded project. NSERC's involvement in the final stage of this work will facilitate an expanded scope of laboratory research, generating new test techniques to better predict the maximum pressures exerted on fill barricades, and new knowledge about CPB resistance to dynamic loads. These fundamental results will in turn aid in a better interpretation of prototype field trials, and lead to new design approaches for specifying backfill barricades and for mining under backfill.