The invention relates to the technology of rib spalling. In the present invention, adjacent support anchors are tightly connected with each other by anchor cables; each of the support anchors are at least connected with an anchor cable tightly extending from four different directions, so that each of the anchor cables constitutes a mesh structure, and a flexible gap corresponding to the thickness of the support anchor is formed between the inner flexible support net and the outer support net at the anchor cable, which not only allows the support anchor to tighten an anchor bolt, but also makes the anchor bolt in the entire region form a whole.