Abstract:In order to study the filling characteristics of tailings after fine-grained tailings loss during actual filling, taking 8% of finegrained loss in cemented filling of open stope and tailing in a certain iron mine as the experiment background, the basic physical properties and particle size composition of underflow tailings were measured, and the natural settlement, bleeding, slump and block strength ratio tests were carried out, and the test data were compared with the test data of unclassified tailings. The results show that the non-uniformity co-efficient of underflow tailings is less than that of unclassified tailings after 8% fine-grained loss, but the degree of non-uniformity is still good, and it is easy to compact; the natural settling time of underflow tailings is half shorter than that of full tailings, and the coarse particles have settled to close contact after 10 minutes; the slump of underflow tailing is obviously larger, and the loss of fine-grained tailings about 8% will greatly increase the slurry slump; at the same concentration and under the condition of high cement sand ratio, the strength of underflow tailings is about 2~5 times of that of unclassified tailings. Combined with the test results, it is recommended that the best lime-sand ratio of stope filling slurry with first and second step is 1∶10 and 1∶15 respectively, and the concentration is 82%.