Deformation analysis and support optimization of adit surrounding rock under overburden load disturbance

The traditional convergence instrument, 3D laser scanning and other monitoring technologies for the deformation of surrounding rock in the mine roadway can not meet the comprehensive monitoring requirements of complex projects. The technologies have low real-time and automatic monitoring degree, and do not have the capability of long-distance, high-precision and large-area monitoring. The existing optical fiber sensing technology only monitors the single parameter of the surrounding rock in the roadway. It can not comprehensively analyze the stability of the surrounding rock in the roadway. Taking the main adit of a coal mine as the engineering background, the stability of surrounding rock before and after the filling above the adit is studied by numerical simulation. The results show that the filling engineering causes the bearing pressure of surrounding rock on both sides of the adit to rise with asymmetric distribution. The maximum subsidence of the top plate increases from 8.3 mm before filling to 22.1 mm. The maximum floor heave increases from 4.0 mm to 8.5 mm. The maximum increase of the displacement of the two sides is 16.2 mm. The deformation of the surrounding rock corresponds strongly to the bearing pressure, which increases with the thickness of the filling above the adit. The fiber Bragg grating (FBG) sensor is used to construct the adit surrounding rock deformation monitoring system. The FBG sensor is set at the adit section to monitor the opening of the adit arch crown crack, the deformation of the roof, floor and both sides, and the stress and strain of the section. The local deformation of the surrounding rock is analyzed through the real-time spectrum. The results show that the adit roof is obviously under pressure under the influence of the disturbance of the overburden load under the existing condition of stone masonry arch support. The maximum subsidence of the roof is about 30 mm, forming a crack about 2 mm wide. The monitoring results are consistent with the numerical simulation and field observation results. The result verifies the effectiveness of the FBG-based adit surrounding rock stability monitoring method. According to the monitoring results, the reinforcement support scheme of bolt+T-shaped steel plate is proposed for the weak part of the adit support. The support effect is verified by numerical simulation. The results show that after the optimized support scheme, the maximum subsidence of the adit roof under the disturbance of overburden load is 11.3 mm. The maximum displacement of the two sides is 12.04 mm, and the average reduction of the surrounding rock deformation is 48.8%. The scheme improves the stability of the surrounding rock.