Abstract
When a traffic tunnel passes through special strata such as soft rock with high geo-stress, expansive rock, and fault fracture zones, the traditional supporting structure is often destroyed due to complicated loads, which threatens the construction and operation safety of tunnel engineering. Concrete-filled steel tubular (CFST) structure gives full play to the respective advantages of steel and concrete and has better bearing capacity and economic benefits than traditional support structure, which has achieved good results in some underground engineering applications. In order to promote the application of CFST in the construction of traffic tunnels with complex geological conditions and improve the bearing capacity of the initial supporting structure of tunnels, the influencing factors of the bearing capacity of CFST arch were studied by numerical simulation. The main achievements are as follows: (1) The load-displacement curves of CFST members under different material parameters are basically consistent. CFST members have significant restrictions on displacement in the elastic stage and have high ultimate bearing capacity. Although the bearing capacity decreases obviously after reaching the peak, it shows good extension performance. (2) The height of the steel tube section, the thickness of the steel tube wall and the grade of the core concrete have an approximately linear positive correlation with the bearing capacity of CFST arch, but the influence of these three factors on the bearing capacity of CFST arch decreases in turn, and when the grade of core concrete increases above C50, it has no significant effect on the bearing capacity of members.
Highlights
Concrete-filled steel tubular (CFST) structure is a composite structure made of steel tube confined concrete, which gives full play to the performance advantages of steel and concrete and has better bearing level and ductility
When the section height of CFST increases from 170 mm to 220 mm, the ultimate bearing capacity of circular members increases by 301.42 kPa, with an increase of 29.69%; The residual bearing capacity increased by 186.13 kPa, with an increase of 54.68%; The elastic limit load is increased by 33.75 kPa, with an increase of 5.02%
The ultimate bearing capacity of triangular members is increased by 288.31 kPa, with an increase of 29.11%; The residual bearing capacity increased by 216.23 kPa, with an increase of 72.25%; The elastic limit load is increased by 2.10 kPa, with an increase of 0.45%
Summary
Concrete-filled steel tubular (CFST) structure is a composite structure made of steel tube confined concrete, which gives full play to the performance advantages of steel and concrete and has better bearing level and ductility. Relevant scholars have studied the CFST support technology from the aspects of theoretical model, structural experiment, numerical simulation and engineering test, accumulated valuable experience and important data, and continuously promoted the popularization of CFST support in tunnel and underground engineering. Zhang Xiaonan et al [5] studied the compressive and flexural mechanical properties of CFST circular supports through laboratory tests and numerical simulation, which can provide a reference for the structural system. Hou Hetao et al [7] studied the mechanical characteristics of thin-walled concrete-filled steel tubular arch in tunnel support and developed a new type of plug-in grouting joint. Wang Zhichao et al [11] studied the construction mechanical properties of π-shaped steel-concrete composite structure in the application of loess tunnel and put forward appropriate new structural design parameters. Xiang song Kong et al [12] studied the bearing performance of CFST supports through secondary development numerical simulation and similar simulation experiments
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