How Do Self-Drilling Hollow Bolts Reinforce Fractured Slopes?

When constructing expressways or railways, it is often encountered that there are high and steep slopes on the side of the road. If the slope geology is relatively loose or fragmented, it may collapse during the rainy season, damage the road surface and even cause traffic accidents. Therefore, it is necessary to carry out certain management and protection of these slopes.



In view of the development of fractured slope joints and serious rock fragmentation, it is considered to strengthen the slope with shotcrete support. However, ordinary mortar bolts have encountered some insurmountable problems, such as collapsed holes, stuck drills, and insufficient grouting. These problems have a great impact on construction safety and project quality. To solve these problems, we must start with the bolt itself. Compared with the traditional mortar bolt, the self-drilling hollow bolt has a great improvement. It penetrates into the cracks of the rock mass, ensures that the slurry is filled with full and dense, and improves the internal structure of the rock mass, so as to achieve the effect of stabilizing the surrounding rock.

Self-drilling hollow bolt is a new type of support material, which integrates drilling, grouting, and anchoring functions.



Different from ordinary mortar bolts, the construction process of self-drilling hollow bolts in strengthening fractured slopes is relatively simple. The construction process of a self-drilling hollow bolt is generally divided into 4 steps.

1. Preparations: Prepare self-drilling hollow bolts, anchoring rigs, grouting machines, and other related equipment according to the design requirements, and check whether the functions of each piece of equipment are normal.

2. Install the hollow bar: connect the anchor rod with the appropriate drill bit and drilling rig, and connect it with the grouting machine through the rotary grouting adapter, adjust the position and drilling angle of the drilling rig, and prepare for drilling construction.

3. Drilling construction: start the rig to start drilling. During the drilling process, the grouting machine is turned on to prepare the slurry and the grouting is performed simultaneously. The grouting adopts secondary grouting. The water-cement ratio for the first time is controlled at about 1:1, which plays the role of clearing holes and initially filling the cracks of the rock mass. The water-cement ratio for the second time is about 0.45~0.6: 1. Both groutings are under specific pressure, and the grouting pressure should be treated separately. In the general crushing area, the grouting pressure should be controlled above 2MPa. In the severe crushing area, the first time is about 1.5MPa, and the second time can be increased to 2MPa.

4. Install backing plates and nuts: After the slurry solidifies, you can choose to install steel beams or steel mesh, and then install backing plates and nuts on the exposed section of the bolt to transmit the pressure of the slope deformation.



Self-drilling hollow rock bolts have great advantages in strengthening fractured slopes, saving steel, convenient construction, easy control of grouting pressure, can effectively increase grouting pressure, increase grouting amount, and effectively increase the bonding force between the rod body and the surrounding rock. So as to play a better anchoring effect.