1 General Principles
1.0.1 So as to make the design and construction of bolt- shotcrete support project conform to requirements of advanced technology, economic feasibility, safety and application and guarantee quality, the standard is worked out.
1.0.2 The national standard is suitable for the design and construction of underground mine, access tunnel, hydraulic tunnel and all classes of cavern bolt-shotcrete support. It is also suitable for the all classes of rock side slopes bolt-shotcrete support construction.
1.0.3 For the design and construction of bolt-shotcrete support, the geologic investigation working for project must be done well and adjusted measures to local conditions, exactly and effectively reinforce wall rock, made full use of the self-supporting property of the wall rock.
1.0.4 The design and construction of bolt-shotcrete support not only observes the standard, but also conforms to relevant regulations of the current national standards.
2 Terms and Symbols
2.1 Terms
2.1.1 Initial support
When the design required the permanent support of the tunnel to be finished in stages, the timely construction support after tunnel excavation is called initial support.
2.1.2 Final support
After tunnel initial support is completed, when the wall rock is basically stabilized, it is that the tunnel periphery relative displacement and displacement velocity reach prescribed requirement, the final construction support is called final support.
2.1.3 Haunch
The haunch is the part from tunnel arch top to midpoint of arch springing arc length.
2.1.4 Convergence of tunnel inner perimeter
The distance variation of the tunnel periphery corresponding two points called convergence of tunnel inner perimeter.
2.1.5 Anchoring force
The generant restraining force of bolt to wall rock is called anchoring force.
2.1.6 Anti-pullforce
The force preventing bolt from pulling out from the rock mass is called anti-pull force.
2.1.7 Wetted perimeter
The perimeter of the wetted cross-section hydraulic tunnel is called wetted perimeter.
2.1.8 Point-loading strength index
It indicates the point-loading strength when the cylindrical standard test pieces with 50mm diameter are pressurized in radial direction.
2.1.9 System bolt
So as to make wall rock stabilize, the bolt groups on the tunnel periphery according to certain format collocation is called system bolt.
2.1.10 Prestress bolt
The prestress bolt is composed of anchor head, prestress bar and anchorage body, it indicates the long bolt which makes use of the elastic elongation of the prestress bar freedom section (stretching section) applying prestress to bolt so as to supply required initiative support tensile force. The specified prestress bolt in the national standard is the bolt whose amount of prestress is more than 200kN and its length is more than 8.0m.
2.1.11 Split set
The longitudinal split thin-wall steel tube is forced to thrust in the drill less than its outer diameter and take the friction and anchoring effect in virtue of radial thrust of steel tube to pore wall.
2.1.12 Swellex bolt
The abnormal cavity bolt manufactured by thin-wall steel tube is sent into the blast hole, take the anchoring effect by the generant friction which is produced by the high pressure water injection into the member and made it bulge.
2.1.13 Self-drilling bolt
It is integrated with blast hole, slurry injection and anchorage. The hollow drill string is the bolt as body of rod.
2.1.14 Shotcrete
The concrete mixture mixed with a certain ratio is sent to the injector head along pipe using compressed air or miscellaneous dynamics, they are injected vertically onto the sprayed surface with higher velocity, depending on the cement and aggregate continuous impaction and consolidation, the shotcrete is formed.
2.1.15 Sand enveloped by cement (SEC) shotcrete
The cement enveloped sand grout mixed with certain ratio and mixtures giving priority to coarse aggregate are sent to the sprayer mouth by using sand pump and injection machine respectively, after mixture, they are sprayed to the sprayed surface with high speed, and the formed concrete is called Sand enveloped by cement (SEC) shotcrete.
