Research on stability control of roadway intersections with nested variable cross-section in deep mine

In deep mines, it is pretty important to maintain the stability of surrounding rock of development roadway with long service life.However, there are often some problems, such as large deformation and support failure in the deep soft rock environment, because of the close connection of the two intersection points in shaft bottom.This study draws on the surrounding rock control of intersection group of nested variable cross-section roadway in a coal mine as the engineering background.Through field investigation and geological survey, it clarifies the properties of 3.9 m close nested connection structure, variable cross-section and large cross-section, as well as the characteristics of large-scale layer crossing.It also analyzes the reasons for the failure of its original support scheme under the deep rheological surrounding rock.For this reason, the refined numerical modeling is carried out, and results indicate that the stress of the main roadway at the side of the triangular rock pillar has a stress subarea of "reduction-superposition-recovery" along the axial direction.The smaller the intersection angle of the two roadways, the longer the axial distance of the region, and the larger the peak value and range of the abutment pressure.With the increasing of cross-section, the stress concentration range of surrounding rock increases in both horizontal and vertical directions.The plastic zone is overlapped multiple times in the connecting section, and its width is increased more than twice.At the same time, there is an obvious discontinuity in the crossing layer, and the range of the variable cross-section roadway section and the connecting section are rapidly expanded.Therefore, this paper put forward a sectional reinforcement control scheme based on hollow grouting anchor cable, and through on-site observation and monitoring, the reinforcement support effectively ensures the stability of the surrounding rock of the deep well intersection group.