At present, new reinforcement technologies such as rock anchors that utilize the self-stabilizing ability of the stratum have been greatly developed. The safety protection of high slopes in collapsible loess and sandy egg strata has always been a difficult problem for traditional reinforcement technology and technology. The self-drilling rock bolt retaining wall can solve this problem very well.
Self-drilling rock bolt retaining wall mainly integrates the working principles of prestressed anchor cable retaining wall, soil nailing wall, conventional bolt retaining wall, high-pressure grouting anchoring technology, and new material itself. The outer end of the bolt is fixed on the frame retaining wall, and the other end is anchored in the stable rock mass within the sliding surface. The anchor rod generates a compressive stress zone within a certain anchoring range, and the pressure surface is formed by transmitting force through the frame retaining wall and shotcrete slope protection, which fundamentally improves the mechanical properties of the rock mass, and changes the passive retaining structure of the traditional retaining structure to make full use of the rock mass. The active protection of the self-stabilizing ability of the body itself can effectively control the displacement of the rock mass.
Self-drilling rock bolts are hollow threaded bolts made of non-ordinary steel. The bolts are used as drill pipes and are equipped with disposable wear-resistant carbide button drill bits. The drill pipe and the bolt are combined into one. Self-drilling rock bolts have the characteristics of high tensile, flexural, shear, and surface bonding strength. The hollow of the bolt is used as the grouting channel so that the grout can be filled in a ring form from the bottom of the hole to the orifice, which ensures that the annular space and the geotechnical space are filled fully, and there is no need to use the casing for the formation with easily collapsed holes. Drilling, putting rods, grouting and anchoring can be completed at one time to improve efficiency.
The thread of the self-drilling rock bolt is continuous, therefore, it can be cut at any position or can be lengthened with a connecting sleeve, which is convenient for use in difficult environments and has a wide range of adaptability. The rod body adopts a special thread to increase the anchoring force, the anchor rod has strong resistance to torque, and the drilling depth is large, which is convenient to increase the bearing capacity by increasing the anchoring depth. The self-drilling rock bolt can be used for grouting while drilling in the soft soil layer or in the stratum where the hole needs to be reinforced. Combined with increasing the grouting pressure, the grouting in the hole can be filled, and the final formed column can reach the diameter of the drill bit. 1.5~2.5 times, making the rod body, cement slurry, and formation tightly combined, firm, and reliable.
The wet drilling method is adopted for drilling. The water is replaced by pure cement slurry with a water-cement ratio of 0.7~0.8, and the pressure of the cement slurry is controlled at 0.5~2MPa. The cement slurry can play a cementing role to cement the non-clay soil together. Through the precession of the bolt, the cement slurry is radiated into the soil layer from the grouting of the drill bit, and the cemented soil layer is smashed into pieces by the drill bit and squeezed into the hole. The wall plays the role of reinforcing the hole wall, so as not to collapse the hole.
After the anchor rod is drilled to the design depth, continue to rotate the anchor rod without advancing it. Use the air pressure of the drilling rig to clean the loose soil and debris in the hole. Connect the anchor rod head with a hose to the grouting pump, and implement it through the anchor rod hollow channel and drill hole. Grouting. The mortar is filled in sequence from the bottom of the hole to the outside and the air in the hole is exhausted. When grouting, pressure grouting can be used, and the grout can better fill the cracks of the rock mass and play a better anchoring effect.
Self-drilling rock bolt retaining walls are used in the protection of high slopes in collapsible loess and sandy egg strata, which can greatly reduce the amount of work, occupy less land, overcome the difficulty of forming holes in the stratum, greatly improve work efficiency and save project investment; at the same time, it can also strengthen the pullout resistance of the anchor rod, thereby optimizing the construction plan.
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