Abstract
With the recovery of the wind oxidation zone in 13116 working face of Gubei Coal Mine as the engineering background, the occurrence condition of coal seam and the bedrock wind oxidation zone characteristics were analyzed. On this basis, the time‐varying rheological parameters of superfine cement slurry and the permeability characteristic parameters of roof strata in wind oxidation zone were measured; then, a grout diffusion equation was established with the parameters obtained previously for the permeability characteristics of roof strata in the wind oxidation zone of Gubei Coal Mine. The grouting design was applied in actual engineering projects and its engineering effect has been proved to be satisfactory. The results indicate that superfine cement slurry whose water‐cement ratio is 0.6 is a typical power‐law slurry consistent with time‐varying rheological parameters. It has better rheological properties during pumpable period, and its rheological parameters can be controlled by highly dispersive nano‐SiO2 and polycarboxylate superplasticizer. For grouting in wind oxidized zone, comprehensive consideration must be given to effective permeability Ke, porosity ∅ , and time‐varying rheological parameters c0, k, and n. To realize effective diffusion of grouting in coal and rock mass, grouting pressure and diffusion time must be reasonably designed rather than excessively increased.
Highlights
Under the joint impact of sedimentary water and weathered damage, the coal roof in wind oxidation zone becomes hard to manage due to the rise in porosity and the consequent fall in strength and bearing capacity
To mine in wind oxidation zone, water flowing fracture zone and caving zone may spread over upper aquifer, which triggers water and sand inrush and causes production accidents in the end
In view of the characteristics of strata weathered damage and mine pressure behavior of wind oxidation zone, pregrouting reinforcement of coal roof is a key technology to solve the problems associated with mining in wind oxidation zone
Summary
Under the joint impact of sedimentary water and weathered damage, the coal roof in wind oxidation zone becomes hard to manage due to the rise in porosity and the consequent fall in strength and bearing capacity. According to the characteristics of wind oxidation zone in 39017 working face of Gong III shaft in Pingshuo Coal Mine, Yang and Shi [6] put forward many feasible measures to control surrounding rock, like advanced grouting reinforcement in assistant haulage roadway, grouting before working face support, improving setting load of support, and mesh placement on top beam. With the recovery of the wind oxidation zone in 13116 working face of Gubei Coal Mine as the engineering background, this study analyzed the occurrence condition of coal seam, the distribution characteristics of upper aquifer and aquiclude, and the bedrock wind oxidation zone characteristics On this basis, the time-varying rheological parameters of superfine cement slurry and the permeability characteristic parameters of roof strata in wind oxidation zone were measured. E grouting design for the project under study was optimized according to the results obtained, and its engineering effect has been proved to be satisfactory, which provides reference and instruction for grouting reinforcement under similar geological conditions
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