What is the role and mechanism of rock bolt on the tunnel surrounding rock？

System anchors are groups of anchors applied radially along the cross-section of a tunnel where the rock mass is excavated. The emphasis is on the joint action of the anchors to form a bearing ring, i.e. the "group anchor effect". It can slow down the deformation rate of surrounding rock and improve the self-supporting capacity of surrounding rock. In the anchor spray support plays an important role (anchor spray support: spray concrete, reinforcing mesh, system anchor

Local anchor refers to the installation of a small number of anchors, such as locking anchor pipe, in a certain area and direction, with a certain external insertion angle. In order to strengthen the local surrounding rock stability and bearing capacity.

According to engineering experience, the length of the locking anchor pipe, the external insertion angle, whether grouting, and the welding method with the steel arch frame will affect the settlement of the arch and slow down the recovery rate of the surrounding rock on both sides. Therefore, extra attention should be paid, if the settlement of the arch encroachment limit (secondary lining), the arch should be replaced. It will delay the project progress and increase the project cost.

Overrunning anchor refers to a group of anchors applied to the front of the palm face along the excavation contour line at a certain outward insertion angle. Over-head anchors emphasize over-head support, pre-strengthening the surrounding rock in front, forming a reinforcement circle to ensure the safety of tunnel excavation. Classification: according to its reinforcement area of surrounding rock: system anchor, local anchor, overrun anchor. The anchors in anchor spray support mainly refer to system anchors and local anchors.