Failure characteristics and control technology of surrounding rock during roadway passing collapse column.

The collapse column may result in failure of the surrounding rock during roadway excavation. It is of considerable importance to elucidate the failure characteristics and develop the corresponding control technologies for the surrounding rock. A discrete fracture mesh (DFN) and a strain-softening constitutive model are employed to simulate the properties of a collapse column. The stress zoning model was developed to characterize the rock surrounding the collapse column. Additionally, the zoned support technology was proposed to stabilize the roadway surrounding the rock. From the center outward, the results indicate that the collapse column can be individually divided into four zones: an internal impact zone of the collapse column, a stress decreasing zone, a stress increasing zone, and an initial stress zone. Upon the visibility of the collapse column, the tensile failure occurs in the roof, leading to a decrease in stress in front of the roadway and an increase in stress on both sides of the collapse column. The collapse amplifies the range of plastic failure by inducing an overlap between the roof stress and the stress elevation zones. The impact zone of the collapse column was reinforced by means of an integrated support system consisting of "pre-grouting, bolt cable mesh, and steel shed". The "bolt cable mesh" provides integrated support beyond the area affected by the collapse column. Following a 20d excavation period, the roof and the two sides were stabilized, with an effectively controlling for the surrounding rock.