The study of the stability of a tunnel when its cross-section is enlarged that meets the demand of a large cross-section for extracting ore, but is also safe for mining, is the subject for this paper. The use of rock failure process analysis code (RFPA2D) simulation is used to analyse the stability of sublevel caving without floor pillars and several large cross-section drifts. The primary stress, displacement and failure zone of these kinds of cross-section of tunnel is calculated. The conclusion is that the tunnel is safe when its cross-section is 6.5m×3.0m and it is 1.5m over the lower wall. This gives some references for the operations of underground mining.
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