Support Measures and Stability Law of Large Cross Section Chamber with Compound Roof

Based on geological conditions of return air roadway of 2302 working face of Lu’an Group, using the methods of theoretical analysis and numerical simulation, we researched the surrounding rock stress and deformation law of compound roof during the process of roadway tunneling, analyzed the stability evolution characteristics of space surrounding rock of large-section composite roof formed after the excavation and drilling site at the roadway side, revealed the stability degradation law of the surrounding rock in the large-section composite roof chamber after the secondary disturbance, proposed “high strength anchor bolt +double reinforced ladder beam + anchor cable + steel fabric mesh” combination supporting scheme. The results show that the deformation of the two sides is 270 mm and roof is more than 150 mm after the formation of the return air drift in 2302 working face. The disturbance range of roof stress is more than 13 m. The excavation in the drilling field caused secondary rock disturbance in the roadway, and the deterioration of the return air drift stability in 2302 working face is accelerated. The roof subsidence increased to 200 mm, and the roof stress disturbance range increased to more than 16 m. According to the observation of the deformation amount of surrounding rock in the field, the deformation amount of surrounding rock is below 120 mm after the combined support scheme is adopted in the roadway and drilling field.