Analogical model test and theoretical analysis on zonal disintegration based on filed monitoring in deep tunnel

Abstract

Field monitoring carried out in a deep tunnel of the Dingji coal mine in China confirmed the zonal disintegration phenomenon by using the borehole TV. Based on field monitoring, an analogical model test was conducted to research the fracture shape and forming conditions of the rock mass in the Dingji mine. To perform the model test, an analogical material and optical sensor were developed independently. Through the test, the occurrence of zonal disintegration was confirmed and the forming process was monitored. The fracture pattern of zonal disintegration was determined, and the radii of the fractured zones were found to fulfil the relationship of geometric progression. The displacement laws of surrounding rocks during zonal disintegration were obtained and found to be non-monotonic. The test results are in agreement with the field-monitoring results. Through a theory analysis based on fracture mechanics, the mechanism of zonal disintegration was revealed. The fracture zones occur as circles concentric to the cavern periphery, which is the “false face”. Each fracture zone ruptures at the elastic–plastic boundary of surrounding rocks and then coalesces into a circle. The geometric progression ratio was determined; it is related to the mechanical parameters and ground stress of the surrounding rocks and calculated as follows: And the mechanism of the non-monotonic displacement law is revealed; the continuous formation of the “false face” causes the geostress redistribution and crack opening.

Acknowledgements

This work was supported by the 111 Project (No. B13024) and Program for Changjiang Scholars and Innovative Research Team in University (No. IRT1125); the National Natural Science Foundations of China (Grant No. 51209074); the China Postdoctoral Science Foundation (Grant No. 2012M511189 and 2013T60494); the Fundamental Research Funds for the Central Universities (Grant No. 2012B02714), supported by the State Key Laboratory For Geomechanics and Deep Underground Engineering, China University of Mining & Technology, Under Grant SKLGDUEK1206; the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering, the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, under grant NO. Z012008, and funded by CRSRI Open Research Program CKWV2012306/KY; and the Key Laboratory of Coal-based CO₂ Capture and Geological Storage Open Research Program 2012KF08. The authors are deeply grateful for this support.