5 Key Points When Supporting the Slopes of Deep Foundation with Self Drilling Anchor Bolts

Self-drilling anchor bolts support construction does not require casing follow-up and is economical and efficient. It is often used in foundation pit support, slope protection, and tunnel advance support projects, and has a good support effect. What are the precautions for self-drilling hollow anchors when supporting the slopes of deep foundation pits in soft soil layers? Today, Sinorock will give you an introduction.

What are self-drilling anchor bolts?

The Self-drilling anchor bolt is the core product of Sinorock, which includes the R-thread system and T-thread system. Sinorock self-drilling anchor bolt size range from R25 to R51, T30 to T200.

The Self-drilling anchor bolt system is composed of a hollow anchor bar, coupler, nut, drill bit, plate, and centralizer. It can combine drilling, grouting, and anchoring in one process. The self-drilling anchor bolt system is safe, efficient, and convenient. It is suitable for broken rock, loose soil, and geological conditions where is difficult to drill holes. It helps to ensure the anchoring effect in complex ground conditions and achieve the best construction result.

What should we pay more attention to?

Self-drilling hollow anchor rod construction is mainly composed of three parts: drilling, drill pipe extension, and grouting. When drilling, high-pressure air or water is usually used to clean the hole to prevent the hole from being blocked. There are several points of attention during the construction process:

1. The earthwork shall be constructed according to the design in vertical layers and horizontal jump sections. Before drilling the self-drilling hollow anchor rod, the slope surface should be sprayed with concrete to reach the corresponding design strength, and then the drilling support construction should be carried out. The excavation and support construction of the next layer is prohibited before the concrete strength and anchoring strength have not reached the design requirements.

The excavation depth of each layer of soil varies with the self-stability of the soil and the specific geological conditions. The excavation height of each layer in sandy soil is 1.0～1.5m, and it can be increased appropriately in cohesive soil.

2. After the earth excavation, the slope is repaired. According to the design drawings, the horizontal and vertical distances of the anchor rods are first determined to determine the hole positions, and then the support construction is carried out.

3. Generally, DTH drills or anchor drills are used for drilling. When drilling, the hollow rod body is connected to the drill bit, which is both a drill rod and an anchor rod. If the length of a single anchor rod does not meet the design requirements, the second, third, or more should be connected with a connecting sleeve until the drill reaches the design depth.

4. During the drilling process of the self-drilling hollow anchor rod, the method of grouting while drilling can be used. On the one hand, the hole can be cleaned, and on the other hand, the slurry can penetrate the soil around the hole wall during the drilling process. The fissure and the anchor body form an anchor with a larger diameter. This kind of construction method adopts secondary grouting. The water-cement ratio of the first grouting should be 1:1, the pressure should not be less than 0.6MPa, the second grouting pressure should not be less than 1.6 MPa, and the strength grade should not be less than M20.

5. After the grouting is completed and the grout has solidified to a certain strength, the waist beam can be installed on the exposed end of the self-drilling hollow anchor rod, and then the backing plate and nuts are installed to fix the anchor rod so that the anchor rod and the shotcrete panel form a whole. Force.

The application of self-drilling hollow anchor rods in foundation pit support can simplify the construction process, shorten the construction period, and reduce the overall cost of the project. It has become one of the very economical and efficient methods for foundation pit support.