Abstract: To large section chamber with fractured surrounding rock and repeatedly repairing, strong rheology cannot be controlled effectively with bolt-wire-cable support style. According to the repeatedly repairing 39# pump house of Zhongmacun Colliery, Jiaozuo Coal Company, the main factors on instability of surrounding rock include strong rheology strata influenced by high stress, uneven loading on steel timbers. Repair scheme combined initiative and passive support is proposed, which includes primary bolt-wire mesh-cable, secondary closed steel timber and third grouting reinforcement. Original and repairing support is analyzed with creep numerical simulation. The results indicate that shrinkage percentage of chamber section is 92.2% within 360 days, and the maximum roof subsidence is 2 792 mm, and accelerated creep phase of surrounding rock appears. The maximum roof subsidence is 56.8 mm within 1 000 days, and stable creep phase of surrounding rock appears with repairing method. Cables are anchored in intact rock mass, but most bolts are in plastic zone. Density of stress contour lines is very intensive outside of grouting range, whose peak value is increasing and moving gradually to deep surrounding rock with the extension of time. The field experiment shows that maximum displacement of chamber is 18 mm, and convergence ratio is less than 0.5 mm/d after 224 days. So the repair scheme of the chamber is successful.

Key words: large section, fracture rock mass, repeatedly repairing, creep simulation, combined support