Abstract
Because of the limitation of mining techniques and economic conditions, large amounts of residual coal resources have been left in underground coal mines around the world. Currently, with mining technology gradually developing, residual coal can possibly be remined. However, when residual coal is remined, caving areas might form, which can seriously affect the safety of coal mining. Hence, grouting technology is put forward as one of the most effective technologies to solve this problem. To study the grouting diffusion in fractured rock mass, this paper developed a visualization platform of grouting diffusion and a three-dimensional grouting experimental system that can monitor the grout diffusion range, diffusion time and grout pressure; then, a grouting experiment is conducted based on this system. After that, the pattern of the grouting pressure variation, grout flow and grout diffusion surface are analyzed. The relationship among some factors, such as the grouting diffusion radius, compressive strength of the grouted gravel, porosity, water-cement ratio, grouting pressure, grouting time, permeability coefficient and level of grout, is quantitatively analyzed by using MATLAB. The study results show that the flow pattern of the grout in fractured porous rock mass has a parabolic shape from the grouting hole to the bottom. The lower the level is, the larger the diffusion range of the grout is. The grouting pressure has the greatest influence on the grouting diffusion radius, followed by the grouting horizon and water-cement ratio. The grouting permeability coefficient has the least influence on the grouting diffusion radius. The grout water-cement ratio has the greatest influence on the strength of the grouted gravel, followed by the grouting permeability. The grouting pressure coefficient has the least amount of influence on the grouting diffusion radius. According to the results, the grouting parameters are designed, and a layered progressive grouting method is proposed. Finally, borehole observation and a core mechanical property test are conducted to verify the application effect. This grouting technology can contribute to the redevelopment and efficient utilization of wasted underground coal resources.
Highlights
Due to technique limitations and economic conditions, some relatively outdated coal mining methods, such as the room pillar type and lane column type, have been widely used throughout the world for a considerable portion of coal mining history
With the development of mining technology, the redevelopment and utilization of residual coal has become possible. Recycling this part of coal resources can fulfill the requirements for the efficient development and utilization of resources
Residual coal repeated mining refers to the use of mechanized coal mining technology to mine residual coal left in old mining areas [2]
Summary
Due to technique limitations and economic conditions, some relatively outdated coal mining methods, such as the room pillar type and lane column type, have been widely used throughout the world for a considerable portion of coal mining history. With the development of mining technology, the redevelopment and utilization of residual coal has become possible. Recycling this part of coal resources can fulfill the requirements for the efficient development and utilization of resources. It is a requirement for coal mining companies to maintain their long-term development and can have a significant impact on the sustainable development of old mining areas. Several collapsed zones, which seriously influence the production and safety of the coal mines, exist in residual coal repeated mining areas. Grouting in the rock mass of a collapsed zone is one of the most effective technologies for solving this problem. The key to solving this problem is to determine the law of grouting diffusion in a fractured rock mass
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