Technology and application of large curtain grouting water conservation mining based on macroscopic and mesoscopic characteristics of rock mass

The construction of curtain grouting wall at the groundwater runoff channel is an important balance means between the development of mineral resources and the protection of groundwater resources. With the increase of inten- sity and depth of mining operations,the construction of large-scale curtain wall faces the problems of high drilling cost,large water pressure difference between the inside and outside of the wall,and low closure rate of the wall. In view of the above problems,the authors adopt the method of macro and micro characteristics analysis on the injected medium: macroscopically study the development characteristics and hydrogeological conditions of the injected media,and micro- scopically study the development characteristics and geometric parameters of the injected media based on the analysis of micro CT,comprehensively analyze the scientific location of large curtain wall,drilling technology,grouting materials and the selection of applicability ratio,grouting pressure and other issues by combining macroscopical and microscopi- cal analysis,and make use of water drainage test,drilling core,drilling cuttings components to analyze and evaluate the curtain grouting effect. The results show that for the cracks with small opening,pure water slurry should be used for pressure grouting filling,and for the karst stratum with large cavities,fly ash can be added into the cement slurry for non-pressure filling. For the cement slurry with water-solid ratio of 0. 6,0. 7,0. 8 and 0. 9,the cement slurry with wa- ter-solid ratio of 2. 0,1. 0,0. 8 and 0. 6 and the cement with corresponding fly ash content of 20% ,20% ,20% ,20%and 30% ,the physical and mechanical properties of the fly ash slurry stone can meet the construction requirements of the curtain wall. The minimum safe thickness of the curtain wall is 7. 84 m,and the grouting pressure to meet the slur- ry diffusion range and construction efficiency is 4-6 MPa. According to the inspection of the inspection hole,the satu- rated compressive strength of the slurry stone sample taken for the filling and pouring of the large cavity is 11. 2 MPa, which fully meets the strength requirements of the wall. In the water discharge test,the water level difference between the inside and outside of the wall reaches 140 m in 7 days,and the closure rate is over 86. 51% . The closure effect of the wall is significant,which meets the design objectives and requirements.