| When the freezing method is used to drill wells in very thick alluvial layers,the stress conditions on the shaft wall are very complicated.During construction,the outer wall will be subjected to strong freezing pressure;after thawing,the inner well wall will be subjected to high water pressure.In particular,high-strength concrete has a large hydration heat and a thick lining hydration heat temperature,which can easily cause temperature-constrained cracks in the shaft wall,which brings difficulties to the water prevention and control work of the deep vertical shaft.To this end,in this paper,according to the engineering conditions of the second auxiliary shaft of Dingji Coal Mine,the experimental study on the structure of the hybrid fiber concrete shaft wall of the freezing wellbore with ultra-thick alluvial layer was conducted.First,based on the optimized raw materials,through the orthogonal test of three factors and three levels,the best mix ratio of the mixed fiber concrete in the frozen shaft wall was obtained,and the relevant performance was tested and supplemented by microscopic analysis.The results show that Although the incorporation of hybrid fibers does not improve the compressive strength of concrete,the tensile strength is significantly improved,and the splitting tensile strength is increased by 41.88%.In addition,the hybrid fibers have significantly improved the crack resistance and impermeability of concrete.Secondly,based on the experimental research results of the hybrid fiber concrete in the frozen shaft wall,and taking into account the effect of the thickness-diameter ratio of the shaft wall structure,the finite element analysis software AN SYS was used to numerically analyze the shaft wall structure model,revealing the stress of the shaft wall structure Characteristics and failure mechanism,and according to the calculation results,fitting the empirical calculation formula of the ultimate bearing capacity of this new type of shaft wall structure.Then,based on the numerical simulation,the optimization group's shaft wall structure similarity model test was carried out,and the ultimate bearing capacity of the shaft wall structure model under uniform load was obtained.The results showed that the hybrid fiber group's ultimate bearing capacity of the shaft wall structure was somewhat different Increase,compared with the benchmark group,the largest increase was 8.71%.The analysis of the failure morphology of the shaft wall structure shows that the hybrid fiber concrete shaft wall structure has significant toughness characteristics and overcomes the brittle defects of high-strength concrete.The model test results are used to verify the empirical formula of the ultimate bearing capacity fitted by numerical simulation.Finally,on the basis of considering the increase coefficient of concrete compressive strength in the shaft wall structure,this kind of optimization design formula for the wall thickness of the shaft wall structure is proposed.The results show that the numerical simulation can be used to effectively reduce the shaft wall thickness thickness.Among them,the thickness of the well wall at the depth of 500m is 1.082m after optimization,which is about 32.75%thinner than that of the conventional design.Comprehensive research shows that the hybrid fiber concrete shaft wall structure improves the toughness and crack resistance of the frozen shaft wall structure,and can obviously improve the brittleness defects of the ordinary high-strength shaft wall structure,and can be used to solve the coal mine ultra-thick alluvial layer frozen shaft wall concrete Cracking water leakage problem.Figure 43 Table 31 Reference 93... |
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