| Water and sand inrush caused by shaft wall rupture is a serious geological hazard that threatens mine safety.There are widely distributed thick aeolian sand layer covering the surface of the auxiliary shaft of the Jinjitan Coal Mine.The floor of the auxiliary ruptured due to the repeat roller compaction of large tonnage vehicles on the floor during a short time,which resulted in water and sand inrush and seriously threatened the safety of the mine.Grouting treatment was implemented and it played an important role in sealing water and sand inrush,which ensured the normal use of the deputy shaft.This paper analyzed the geological conditions and the construction process of shaft management.On-site and indoor model tests and modern analytical testing methods were used to analyze the stress state of the shaft wall and hydraulic pressure response of the post-wall during grouting.Diffusion characteristics of the slurry,sand and water sealing mechanism and microscopic pore characteristics of chemical grouting sand body were also studied.This paper is supported by National Natural Science Fund No.41172291 and National Key R&D Program of China under Grant No.2017YFC0804101.(1)Based on the study of the geological conditions of the well fields and auxiliary inclined wells and the engineering technology of water and sand inrushof the Jinjitan coal mine,the main causes and sources of water and sand inrush in the auxiliary inclined shaft were analyzed,and the reasons for successfully treatment were also discussed.The problems were proposed,such as the force acting on the wall,the response of the pore water pressure behind the wall and the diffusion characteristics of the slurry in the rear of the wall during the grouting treatment.(2)The diffusion characteristics and reinforcement mechanism of cement and chemical grouts were investigated based on the analysis of the field model test.The results showed that the cement grouting reinforced the sand layers as a tree-like propagated grout veins,which cannot completely blocked the pathway of groundwater.The chemical grouting reinforced the sand layers by splitting and infiltration,which took more advantages for sealing off the residual pathway of groundwater.(3)Through the inclined shaft grouting model test,the stress status and the water pressure response process of the shaft wall during grouting conditions were obtained.The wall stress increased and decreased for multiple times during grouting process;after the slurry was fully gelled,the stress of sidewall and roof reduced,and the stress of floor increased.The pore water pressure of the sidewall and the roof experienced low amplitude fluctuations,high amplitude fluctuations and descent processes.The pore water pressure of the floor experienced sharply increase,maintenance and rebound processes.(4)According to the method of particle contact on the diffusion radius of the chemical slurry,it was divided into three types of sand consolidation model: slurry skeleton,transition and particle skeleton.(5)The microscopic characteristics of chemically consolidated sand were studied by mercury intrusion porosimetry and Zeiss 3D-XRM system.Cumulative mercury infiltration and pressure curves all showed S-shaped changes,and the mercuy ejection rate ranges from 52.62% to 99.46%.The slurry is preferably filled with macropores and mesopores during the infiltration process,and the transitional pores and micropores are not substantially filled.The separation ofpores,grouts and sand particles in chemical grout consolidations was performed by image segmentation techniques.The porosity filling rate is inversely proportional to the distance from the cleavage pulse. |
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