Study and application of high-pressure splitting grouting modification technology in coalmine with depth more than 1 000 m

High-pressure splitting grouting modification technology is an important part of the “ support-modification- depressurization” cooperative control technology of the surrounding rock in roadway,with the self-supporting capacity of surrounding rocks improved. In view of the difficulties of bolt support and conventional grouting methods in 121302 machine roadway of Kouzidong mine in China,the modification technology of high-pressure splitting grouting was stud- ied. High-pressure splitting grouting technology and equipment were developed,a mine pneumatic grouting pump was designed with a maximum working pressure exceeding 30 MPa,and micro-nano inorganic organic grouting composite materials D95≤9 μm were applied to carry out the high-pressure grouting modification test in the roadway with depth more than 1 000 m. The changing rules of grouting pressure and flow,grouting volume in one hole,diffusion radius of slurry and other parameters were statistically analyzed. The results show that the grouting pressure and grouting flow are the main controlling factors of splitting grouting technology,and the cutting pressure of grouting on the heading sur- face in advance is about 22 MPa. Grouting process turns to be a high-pressure micro-splitting and permeation grouting when it is carried out at a place of 6 -8 meters lagging working face by grouting flow controlled appropriately. The effect of modification is obvious by high-pressure splitting grouting,with the problem of grouting in roadway 121302 solved. High-pressure pre-grouting process in advance improves the forming state of new roadway,by enhancing the an- choring quality of bolts and cables. The microstructure analysis of SEM shows that the new micro-nano inorganic organ- ic grouting composite materials can be injected into the 2 μm width crack by the high-pressure splitting grouting process. Grouting induration is combined with the coal interface closely under high pressure,and the internal structure of grouting slurry hydrated stone is more compact,indicating that the grouted coal will have higher strength. Nano-in- dentation testing is proceeded,providing that the elastic modulus of coal slurry is higher than that of coal,and the me- chanical properties of coal recombined are better than before.