According to the requirement of the design specification for railway roadbed structure, the anchor bar retaining wall can be applied to the normal area of rocky road, soil nailing wall can be used to the common area of soil and broken soft rock. In the underground water more developed area or loose slope soil, the soil nailing wall is not that suitable. The pre-stressed anchor cable is practical for the soil or rock stratum slope and the foundation reinforcement. The anchoring section should be placed in the stable rock.
In soft or weathered rock, the anchor wall shear strength of the mortar is generally lower than the mortar to the steel rod. So the ultimate tensile strength of the bolt in the soft rock is controlled by the hole wall shear strength. According to the existing pull-out test data, there is big difference between the numerical value of the ultimate tensile force of the soft rock and the weathered rock. The tensile strength is influenced by many conditions and geological factors, such as the rock mass, the buried depth, the underground water, the drilling technology, the grouting method and so on.
Self drilling rock bolting system mainly consists of drill bit, rock bolt, plate, nut, centralizer, couplings and so on. The centralizer is made of polyethylene and rubber, other components are all made of steel or alloy steel. The fully thread on the surface of the rock bolt can ensure the bond of the grouts and the rock bolt body. The centralizer will be placed in the middle part of every rock bolt, in order to ensure the straight of the drill hole and the axial load of the self drilling hollow bolt, the plate and the nut are used to the anchorage of the rock bolt ends and also offer the pre-stress. The hollow design of the rock bolt and the preformed hole on the drill bit makes it convenient to clear the holes with pressure air and then grout. With the help of high quality self drilling rock bolting system, drilling, grouting and anchoring can be done at the same time, which can improve the efficiency by 25%. There is no need to use casing, the grouting is also full filled. Thanks to these advantages this kind of rock bolting system is especially suitable for the stratum construction where there is heavy holes collapse.