Analysis of circular concrete-filled steel tube (CFT) support in high ground stress conditions

• Friction model with coefficient of 0.4 is proposed to model the interface of CFT support.
• The CFT support exhibits a stable deformability and never loses its load capacity in a sudden manner.
• The concrete strength, steel ratio and support radius have critical influences on the load capacity of CFT support.

Concrete-filled steel tubular (CFT) support has been proposed as a new passive support form for controlling the stability of surrounding rock in underground structures, especially for the case of high ground stress. This paper presents a numerical study on the mechanical performance of CFT support. A plastic damage model is used for the concrete and two interface models are adopted to describe the behaviors between the concrete and the steel tube. The feasibility and accuracy of the numerical method are verified by comparing the calculated results with the test observations. The interface behaviors of CFT support has an important influence on its mechanical performance and the friction coefficient of 0.4 is proposed. The results indicate that the load–displacement response of the CFT support could be generally divided into three stages, elastic, elastic–plastic and plastic stages and the CFT support exhibits a stable deformability and never loses its load capacity in a sudden manner. The mechanical performance of the CFT support increases by increasing the concrete strength and the steel ratio; however, the load capacity decreases as the support radius increases.