Abstract:

The stability of roof is the main factor to determine the roadway section size in the underhand slice stoping with cemented filling method. The failure modes, deformation characteristics of cemented tailings backfill roof and mechanical characteristics of reinforcement are studied by similarity simulation and in situ monitoring according to the actual conditions of Wushan copper mine. The experiment of similarity simulation indicates that the failure mode of roof is not affected by the arrangement of reinforcement in the cemented tailings backfill. And in comparison with the horizontal arrangement of reinforcement, the vertical arrangement is more helpful to enhance the overall stability of roof. In situ strain monitoring results show that the distribution of strain state of filling body roof is more complicated compared with the computation result of simply supported beam. In vertical direction, filling body roof is tensile strain. However, tensile and compression strains alternate with the mining process in horizontal and along roadway direction. Relationship between load on reinforcement and time is obtained by monitoring results of 24 reinforcement metres. According to the mechanical characteristics of reinforcement with the mining process, the process could be divided into four stages: i.e. initial tensile stage, relatively stable stage, alternant stage of tensile and compressive states and the bearing stage. In the bearing stage, reinforcements in the roof bear against the maximum compression before roadway is mined. And after the roadway under the roof has been mined out, reinforcements bear the maximum load of tension and show suspension action. The maximum tensional area lies in the crossing roadway roof.

Key words: cemented tailings backfill, roof, mechanical behaviour, similarity simulation, reinforcing plan