The arching effect significantly affects the mechanical properties such as deformation and loading transmission of the granular media. To visually observe the arching process and force chain distribution, with two steel columns set underneath in the device to cause localized deformation, two-dimensional loading model experiments of photoelastic particles were conducted. By exploring the arching mechanism, the following main conclusions were drawn: (1) Two kinds of arches were found; one is called "stress arch", which can block the loading transmission path and shield the passing stress, while the other is an intrinsic arch generated under appropriate compressive state that can cause mesoscopic inhomogeneity of deformation. (2) Both the geometric parameters and the stress state affect the formation of the stress arch; for instance, the accumulating space S of the steel columns will increase the influence range of the stress arch until its disintegration happens, which is consistent with the trap-door experiments. (C) 2020 Elsevier B.V. All rights reserved.