Abstract: Anchor-net-cable coupling support is widely used in roadways and particularly in large broken zones. Since the anchor is not long enough to support the whole range of surrounding rock in a large broken zone, it should consider the influence of anchor support on the design of a combined supporting when using the anchor-net-cable coupling support. Through systematically analyzing the support mechanism of surrounding rock bolt anchorage in large broken zones, the bolt supporting of anchorage bearing coefficient is proposed. Then, a calculation method to quantitatively determine parameters for anchor-net-cable coupling support is derived. The results show that the strong fractured surrounding rocks are divided into a shallow anchored zone and a deep fracture zone. The former can bear part of the surrounding rock as the cable-pallet, and its stability condition when the bearing capacity is greater than the axial force and the fracture zone is effectively controlled. The bearing coefficient of an anchor is in the range of 0.45-0.75 for the large broken zone, which is depending on the anchorage zone, fracture zone, anchor pre-tightening force and anchoring force. In the field test, the convergences of roof-to-floor and two walls are 273 mm and 393 mm, respectively, and the surface displacement tends to be stable. The proposed method for determination of parameters of anchor-net-cable coupling support effectively ensures its regular applications to the roadways.

Key words: large broken zone, anchor-net-cable coupling support, shallow anchored zone, bearing coefficient of anchor