Study Of Surrounding Rock Stress And Control Technology On The Deep Roadway At Fengcheng Diggings

This dissertation relies on the engineering background of “-800 m Air Return Way in Fenglong Mine North District”. Based on the deep surrounding rock pressure and the instability mechanism of roadway, the stepped combined support was proposed, which well applied in engineering practice.A failure mechanism named the collapsing wedge block, rotating circular block, and multi-translational triangular blocks, was built to analyse the deep surrounding rock pressure.Depend on the objective function and constraint condition of upper bound solutions,the pressure was solved with optimization algorithm. By Linear Mohr-Coulomb failure criteria, this paper analyzed the influence of various parameters on the upper bound surrounding rock pressures.With X ray diffraction experiment and field situation analysis, the inflation pressure caused by the swelling soft rock mineral, complex stress field, and unreasonable support scheme are main adverse factors in maintaining the stability of roadway. According to the actual situation, stepped combined support technology was proposed and its superiority was discussed. With basic countermeasures of “restoration, strengthening, consolidation and repair,enlargement”, the support construction could adapt to the deformation of deep rock mass. The choice of the secondary supporting time was researched with the rheological theory.Based on the loose circle theory and theory of suspension, the preliminary design parameters of bolts and anchor cables were designed, and the bolt parameters were calculated by composite bolt-rock bearing structure. To get the optimized anchor cable parameters,orthogonal test was designed between length, diameter and spacing, and A2 B2 C1(length 7 m,diameter 17.80 mm, spacing 1.6 m×1.6 m) was preferred plan.Applied FLAC3 D to simulate 3 different support schemes, the results showed that support effect of scheme 2 and 3 was better than effect of scheme 1, and floor heave was controlled in a large degree. Stepped combined support allowed rock initial deformation, which avoid the problem of bolts and anchor cables carrying out of sync. Stepped combined support controlled surrounding rock deformation efficiently, so it was more reasonable than combined support.Stepped combined support had been applied in engineering practice. With monitoring surrounding rock pressure and displacement, results showed that pressure would be stable about 25 to 30 days; surrounding rock displacement with new support scheme would be stable about 90 days; surrounding rock displacement with original support scheme would not be convergence. In conclusion, stepped combined support controlled roadway displacement efficiently and maintain the stability of surrounding rock.