Tunnel construction is actually a process of stress relief and stress control. It is realized through two steps: excavation and support. That’s to say, through excavation and support, initial condition of surrounding rocks form long-term stable structure.
Control technology refers to a technology which controls deformation in permissible range and ensures tunnel structure keep long-term stability.
Excavation is a method to relieve stress. With different excavation methods, process and degree of stress relief is different.
Support is a method to control stress. Similarly, with different support methods, process and degree of stress control is different.
Hollow bar anchors’ support effect mainly determines adhesive strength and shearing strength between hollow bar anchors and surrounding rocks. But how to enhance hollow bar anchors’ adhesive strength and shearing strength? There are several measures you maybe adopt: properly increase hollow bar anchors’ diameter(equal to increase bond area), change hollow bar anchors’ surface shape and adopt early strength mortar, etc.
Hollow bar anchors produce tensile and shearing force because of surrounding rocks’ deformation and slide. While in continuous dynamic weak surrounding rocks and joint developmental middle-hard rocks, because of different deformation pattern, produced stress is accordingly different.
Besides excavation and support, other constructions are auxiliary, such as transport, dewater, ventilate, measure and advance prediction, etc. All these constructions are also the key for support, so they should not be ignored.