Development of a 3D geomechanical model test system for non-pillar mining with automatically formed roadway and its engineering application

The non-pillar mining technology of roof cutting and pressure releasing with automatically formed roadway(AFR) is a new type of coal mining method, which takes advantage of the mining pressure and rock mass expansion characteristic to automatically form roadways and hence, achieves coal mining without requiring excavating mining roadways and reserving protective coal pillars. In order to study the movement mechanism of overlying strata, the mining pressure behavior and failure mechanism of AFR in the whole mining process of the non-pillar mining with AFR, a 3D geomechanical model test system for non-pillar mining with AFR was independently developed, which composes of reaction and hydraulic loading subsystem, automatic mining and roadway forming subsystem and high-precision real-time monitoring subsystem. The model test system, equipped with a complete set of test devices to simulate the core techniques such as mining, roof pre-splitting and roadway automatic forming, can actually simulate the whole mining process of mining and forming roadway integration by the non-pillar mining technology of roof cutting and pressure releasing with AFR and monitor the mining pressure of whole working face. The geomechanical model tests with different model sizes in the range of 5.5 m in length, 2.4 m in height and 3.0 m in width can be carried out through a combined anti-force device. Taking the China's first working face of N00 technology-S1201-II working face of Ningtiaota Mine Coal as the engineering background, the 3D geomechanical model test was carried out by applying the model test system to study the most complicated N00 technology in non-pillar mining technologies with AFR. The mining pressure behavior of N00 technology was revealed and the control mechanism of the AFR surrounding rock was cleared. The key control positions of AFR were obtained, and the corresponding engineering suggestions were put forward to guide the following field application. The field monitoring results are basically consistent with the model test, which verifies the rationality and effectiveness of the model test system. © 2020, Science Press. All right reserved.