Meitan xuebao (May 2023)
Development and application of coal burst experiment system based on local mine stiffness theory
Abstract
The loading mine stiffness and the post-peak stiffness of a coal pillar are important factors affecting the occurrence of coal bursts. In order to systematically study the mechanism of coal bursts and pillar bursts based on local mine stiffness theory, a laboratory-scale coal burst experiment system has been developed. The system is mainly composed of static loading system, energy storage system, variable stiffness loading system, excavation system and multi-source information monitoring system. The main innovations of the test system are as follows: ① An excavation device is added to the loading system, which can induce the stress concentration of the specimen and the reduction of local mine stiffness through excavation in the pressure-holding state. Coal bursts will occur when the specimen is stressed to its bearing capacity and the local system stiffness is lower than the post-peak stiffness of the specimen. ② The loading system is equipped with an energy storage device of oil cylinder airbag accumulator, which can store energy during loading. ③ A variable stiffness loading device is set up to adjust different loading stiffnesses by adjusting the initial airbag pressure of airbag accumulator. ④ The experiment system can reproduce the whole process of specimen from loading-stabilization-excavation-burst in laboratory, which makes it possible to monitor the strain of coal pillar during the whole process of coal bursts and observe the burst process. The accuracy and reliability of the simulation equipment are verified by preliminary laboratory tests on high-strength concrete blocks and realistic coal samples. The test results show that under the condition of low stiffness loading, the unstable failure of coal pillars can be effectively induced by excavating bottom samples, and the failure position extends from the low stiffness side to the high stiffness side. The damaged central residual coal pillar is dumbbell shaped under the action of top and bottom plate friction, and is cut off at the center by a transverse sawtooth crack penetrating the sample, resulting in a significant reduction in the bearing capacity of the coal pillar. The development of the experiment system can reproduce the whole process of coal bursts from loading, pressure stabilization, excavation and unstable failure in the laboratory from the perspective of local mine stiffness, and can provide an experimental basis for the mechanism of coal bursts in coal mines.
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