1 The mechanism of anchor bolt system

In current tunnel support system, the anchor bolt system is a kind of very effective anchor supporting way, its application is very extensive, the type is more, but it is not very clear that whether the anchor bolt system play a role in tunnel anchor supporting in the end,generally considered that the reinforcement effect of anchor bolt system has four kinds: suspension effect, enhancing effect, the arch effect and the effect of the internal pressure.

In addition to the above four kinds, grid arch plays a part in geological conditions of poor and weak surrounding rock area,which also to early and stability,with the combination effect with the grid arch,anchor bolt system stability under high pressure to a certain extent of primary support is relatively thin, not to make it produce a partial or whole instability,at the same time,the anchor bolt system also can reduce the relative displacement between initial support and surrounding rock, prevent early support from big whole sink. In order to guarantee the stability of the primary support system of anchor bolt in a timely manner, to ensure that the bearing capacity of the primary support, better guarantee the stability of surrounding rock.

2 The selection of anchor bolt system in the tunnel

In accordance with "specification for highway engineering geological investigation and geotechnical engineering survey specification judge”, the chemical composition of waters and nearby waters is similar to groundwater,which has a moderately corrosive on the steel structure, and has weak corrosive to that of rebar in reinforced concrete, in order to ensure the durability of initial support of anchor bolt, primary anchor bolt support system in land should be used more hollow corrosion bolt, waters paragraph should use duplex coating rock bolt.