Anchor bolt supporting technique can give full play to the self-stabilizing ability of the surrounding rock, and is widely used in the surrounding rock support of highway and tunnels. The mortar bolts are most common type of permanent anchor bolts, which have the problem that the grouting is not full. Especially when it is inclined upward or the length is greater than 3m. Due to the overflow of the mortar it is difficult to ensure the fullness of the grouting, there are often gaps in the hole and exposed steel bars. This problem easily leads to the final anchoring effect and can not meeting the design requirements. In addition, when the surrounding rock is broken and loose, the ordinary mortar bolt is difficult to form holes and easy to collapse, which leads to the failure of support.
Advantages of Self-drilling Hollow Bolt
Applicability
The self-drilling hollow bolt has strong applicability, especially for the weak surrounding rock. The anchor bar can be used for drilling and anchoring. The hollow bolt can be directly drilled into the rock and soil body, and the hollow bar can be used as the grouting channel for grouting from inside to outside. It is no need for hole making and casing protection under bad surrounding rock.
Better Grouting Effect
The grouting is from the hole inside to outside. The self-drilling hollow bolt is equipped with plug, so pressure grouting can be realized, and the slurry can permeate quickly and fully along the rock fissure. The slurry has a large diffusion radius, and the surrounding rock will be consolidated into a whole. The purpose of permanent anchoring surrounding rock can be achieved.
Easy to Operate, Fast and Time saving
After the bolt is drilled in place, the hole can be cleared and grouting can be pressed without pulling out the anchor bar. Compared with ordinary mortar bolt, the construction process is simplified, and the construction benefit is obvious.
Can Be Used in Narrow Spaces
Hollow bars can be cut and lengthened at will to achieve the effect of construction in narrow space. At the same time, the continuous thread makes the self-drilling hollow bolts have stronger bond resistance than the smooth steel pipe, which is 2~3 times higher than that of the ordinary mortar bolt.
Self-drilling Hollow Anchor Bar V.S. Mortar Bolt
Taking Hangzhou Luniao Douling tunnel project as an example. Under the same construction conditions, 2m and 5m long ordinary mortar bolts and self-drilling hollow anchor bar were drilled in the general and severe broken areas, respectively.
Pull-out Resistance
As the integrity of rock mass decreases, the pull-out capacity of ordinary mortar bolt decreases more significantly, while the loss of self-drilling hollow anchor bar in severely broken rock mass is small.
Grout Filling Effect
In the general broken area, the grouting pressure of the self-drilling hollow anchor bolt is slightly greater than that of the ordinary mortar bolt. In the severely broken area, the grouting pressure of the hollow anchor bolt is obviously greater than that of the ordinary mortar bolt.
The grouting amount of the bolt in the severely broken area is much higher than that in the general broken area, up to 4 ~ 6 times. The grouting amount of the self-drilling hollow anchor bolt is also significantly larger than that of the ordinary mortar bolt, about 1.5 ~ 2 times.
Summary
Self-drilling hollow bolt is a new type of anchor bolt integrating drilling, grouting and anchoring, which can ensure high construction efficiency and better anchoring effect in complex geological conditions such as broken rock stratum, loose layer and stratum requiring casing protection.
Sinorock is a professional self-drilling anchor bolts manufacturer with more than 10 years of experience in the field of ground support. For questions about self-drilling anchor bolt system and applications, please contact [email protected] or visit our website www.sinorockco.com.