Study On Numerical Simulation And Reasonable Grouting Timing Of Surrounding Rock Grouting A Goaf

The surrounding rock of the roadway along the roadway in the long distance is in the state of high bearing pressure, and it is easy to cause large deformation and instability. The simple supporting mode of bolt can not meet the normal production demand. Engineering practice shows that bolting-grouting combined support technique has excellent support outcome, but the choice of grouting time has enormous implications on grouting quality, which determines the success or failure of grouting engineering and gob roadway. In this paper, theoretical analysis and numerical simulation are adopted to study the dynamic grouting numerical simulation method and the optimal grouting time.Based on the existing research results, this paper analyzed the stress evolution process and failure reason of bolt support on the rib of gob roadway and determined the surrounding rock strength parameters and design basis of grouting range.This paper used the embedded strain-softening constitutive model and FISH language in FLAC3D software to construct the dynamic numerical simulation method, which can determine the grouting range and rock strength improvement range after grouting. Some useful changing rules under the mining influence are obtained through numerical simulation, such as broken zone width, bolt support effect and volumetric strain, porosity and permeability coefficient of the coal rib.These indexes first increase and then decrease along with the advance of working face, which reach the peak value at the 10m position back of the face. Broken zone width of the rib also meets the edge of bolt support range at this position. Therefore, it is the best grouting time in the back of face 10m. At last, the dynamic grouting method was used to analyze the grouting effect under different grouting time, which proved the rationality of the grouting time. And the numerical simulation of grouting reinforcement at different positions of the working face is carried out. By comparing the final subsidence amount of each grouting time, the reasonable grouting time of the roadway is better ahead of face 10m.