Abstract
To address the temperature cracking of concrete in frozen shaft linings in extra-thick alluvial layers in coal mines, a novel shaft lining structure of coal mines consisting of hybrid-fiber-reinforced concrete (HFRC) was developed. Using the Finite Element Method (FEM), a numerical simulation test of the HFRC shaft lining structure with four factors and three levels was carried out, and the mechanical characteristics of the shaft lining structure were obtained. The results show that under a uniform surface load, the maximum hoop stress position of the HFRC shaft lining presents a transition trend from the inside surface to the outside surface; the hoop strain of shaft lining concrete is always a compressive strain, and the inside surface is greater than the outside surface. The empirical formula for the ultimate capacity of this new type of shaft lining structure was obtained by fitting. Compared with the model test results, the maximum relative error of the calculated value is only 6.69%, which provides a certain reference value for designing this kind of shaft lining structure.
Highlights
The shafts of coal mines are very significant to the safety of production in coal mines
According to the dimensional analysis theory, combined with the results of the numerical simulation of the shaft lining model, the empirical formula for calculating the ultimate capacity of the hybrid-fiber-reinforced concrete (HFRC) shaft lining can be derived as follows: Pb = aρb1 ρc2 λd fce. In this formula, Pb stands for the ultimate capacity of the shaft lining, MPa; ρ1 stands for the volume ratio of polyvinyl alcohol fiber (PVAF), %; ρ2 stands for the volume ratio of polypropylene plastic steel fiber (PPSF), %; λ stands for the thickness–diameter ratio, which is the ratio of the thickness of the shaft lining to the inner radius of the shaft lining; fc stands for the axial compressive strength of concrete, MPa; a, b, c, d and e stand for the constant to be solved
Temperature cracking of concrete is easy to occur in frozen shaft linings in extra-thick alluvial layers in Temperature cracking of concrete is easy to occur in frozen shaft linings in extra-thick alluvial coal mines
Summary
The shafts of coal mines are very significant to the safety of production in coal mines. Taking into account the workability of concrete during the construction of the project, Yao et al [18] studied the mechanical properties of concrete with hybrid PPSF and PVAF and carried out a similar model test on the shaft lining structure based on similarity theory. By comparing it with the ordinary concrete group, it was found that hybrid-fiber had little effect on improving the uniaxial compressive strength of concrete. The research results are expected to provide a certain reference for designing this kind of shaft lining structure
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