Abstract
The influence of rise-span ratio on the bearing performance of concrete filled steel tube (CFST) circular arch was studied in this paper, three groups of CFST circular arch specimens with different rise-span ratios (0.154, 0.207, and 0.26) were selected, the six-point uniformly distributed loading was performed, and bearing performance experiments on CFST circular arch specimens with fixed ends were carried out. In this study, the ultimate bearing capacity and deformation failure characteristics of CFST circular arch specimens were obtained. The comparative analysis shows that the deformation evolution of CFST circular arch specimens has experienced compaction stage, elastic stage, elastic-plastic stage, and plastic stage. In the elastic-plastic and plastic deformation stages, the circular arch shows good ductility and bearing capacity. The bearing capacity of the circular arch is significantly affected by the rise-span ratio. Compared with circular arch specimens with a rise-span ratio of 0.154, the yield load of specimens with a rise-span ratio of 0.207 and 0.26 is increased by 50.8% and 61.5%, and the ultimate bearing capacity is increased by 42.7% and 68.3%, respectively. The larger the rise-span ratio, the greater the yield load and ultimate bearing capacity of the specimen and the stronger the deformation resistance of circular arch. The numerical simulation on the bending resistance process of circular arch was performed by ABAQUS to present the compression failure process of steel tube and core concrete. The simulation results are in good agreement with the experimental results. The experimental and simulation results show that the circular arch first yields at the inner side of the arch foot, and the curvature of different positions of the specimen is no longer consistent. When the ultimate bearing capacity is reached, the steel pipe at the arch foot obviously heaves, and the hooping effect of the steel pipe on the concrete is invalid. Based on the above research results, a closed composite support scheme of “bolt mesh shotcrete + vertical elliptical CFST support + steel fiber concrete shotcrete layer + reinforced anchor cable” was proposed for the extremely soft rock roadway and successfully applied in the Qingshuiying coal mine.
Highlights
Concrete filled steel tube (CFST) structure can make full use of the hoop effect of steel tube and the good bearing performance of core concrete. e symbiosis of steel tube and core concrete in mechanical properties greatly increases the strength and bearing capacity. e CFST structure has been widely used in the ground building, and a series of research results of CFSTmembers have been obtained [1,2,3,4,5,6,7,8,9,10,11,12]
Based on the mechanical properties of steel-concrete composite materials, underground cast-in-place CFST support is invented as high-strength support, which is suitable for the support of deep roadway and soft rock roadway
Wang Bo [13], Liu Guolei [27], and Wang Jun [25] studied the mechanical properties of CFST supports in different specifications under concentrated load and improved the overall bearing capacity of the support by welding bending round steel on the tensile side of the support. e development of CFST support technology has been promoted by a large amount of experimental data and results
Summary
Concrete filled steel tube (CFST) structure can make full use of the hoop effect of steel tube and the good bearing performance of core concrete. e symbiosis of steel tube and core concrete in mechanical properties greatly increases the strength and bearing capacity. e CFST structure has been widely used in the ground building, and a series of research results of CFSTmembers have been obtained [1,2,3,4,5,6,7,8,9,10,11,12]. The bearing performance of circular arch members is affected by the rise-span ratio, the strength of core concrete, the content of steel fiber, the thickness of steel pipe wall, the diameter of steel pipe, and the size of bending round steel. Under the condition of uniformly distributed loading and complete fixation of arch foot, He Xiaosheng [28] studied the ultimate bearing capacity of CFST circular arch specimens with different pipe diameters, wall thickness, and welded bending round steel, monitored the displacement at the span and arch foot, and analyzed the deformation characteristics of CFST circular arch specimens. The influence of the rise-span ratio on the bearing performance of CFST circular arch specimens was mainly studied, and the research results were taken as an important reference basis for the section design of CFST support. The composite support scheme of CFST support was proposed and successfully applied to the support engineering of a large section roadway. is study provides successful methods and experience for the support of soft rock roadway in a deep mine
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