Mechanical behaviors analysis on a square-steel-confined-concrete arch centering and its engineering application in a mining project

Abstract

Aiming at the support difficulties of mine galleries under the complex geological conditions of high buried depth, high in situ stress and tectonic fractured zones, a novel square-steel-confined-concrete (SSCC) arch centering supporting system is proposed in this paper. To validate the feasibility of this supporting system, a uniaxial compression test on an SSCC short column is performed and the results illustrate that it has better ductility and higher bearing capacity than the U-shaped column. Numerical analysis on the mechanical behaviors of SSCC arch centering is conducted considering three factors of core concrete strength, steel tube thickness and confinable effect coefficient. Two influence indexes of steel tube thickness (μt) and core concrete strength (μc) influencing the ultimate bearing capacity are put forward and μt has more significant influence. Therefore, an SSCC arch centering (side length 150 mm, tube thickness 8 mm and filled C40 concrete) is determined to perform laboratory and in situ experiments. Combined with numerical simulations, the deformation failure behaviours of the SSCC arch centering are eventually obtained. The laboratory experimental results show that the maximum deformation appears near the spandrel of the arch centering and the ultimate bearing capacity is 1286.9kN. An SSCC and a U-shaped arch centerings have been simultaneously used in the supporting system of the gallery in Zhaolou coal mine project, and the monitoring results (after 157 days) show that their average displacement of the SSCC arch centering is 10.33 mm, which is only 18.3% of that obtained in the U36 arch centering. The above research results indicate that this kind of SSCC arch centering supporting system could efficiently control the deformation of the surrounding rock mass in mining galleries.