Experimental Study on Evolution Process and Failure Mechanism of Overlying Strata in Coal Mining Based on Distributed Strain Sensing Technology
Lei ZHANG1+, Yifei CUI1#, Bin SHI2, Yan YAN3, Heming HAN2
1Tsinghua University, China, 2Nanjing University, China, 3Southwest Jiaotong University, China

The failure of overlying strata in coal mining threaten the safety of roadway and may further induce underground water inrush accidents. Therefore, the deformation monitoring of overlying strata is of great significance. In order to investigate the evolution process and associated failure mechanism of overlying strata under the action of mining, a physical similarity model test was constructed. The distributed strain sensing technology (DSS) and close-range photogrammetry (CRP) technologies were adopted to record the internal and surface displacement information of the model test during coal mining. By comparing the deformation recorded by CRP technology and DSS cables, the feasibility of DSS technology is demonstrated and even though the deformation is small, the DSS technology can still detect strain variation. According to the CRP result, it is found that the deformed area is saddle-shaped in general, forming symmetrical step-shaped fissures at mining face and the initial position of mining. Through analyzing the strain exerts on the DSS cables when the mining face approaches and passes through the installed DSS cables, the deformation characteristics and failure mechanism of overlying strata is addressed and the shear failure appeared at the toe area of key layer may result in the overall collapse of the overlying strata. This study provides practical significance in deformation monitoring and sheds insight into the failure mechanism of overlying strata under coal mining.