The Engineering Support of Self Drilling Anchor Bolt As Soil Nail
1. The application of soil nail.
① It is used in vertical or inclined surface to ensure stability of slope.
② In tunneling construction, it is used for underground pre-support, soil radial reinforcement and surface stability.
③ It is used for reinforcement in railway embankment, slope support, foundation pit support and widening of highway and railway.
2. The stratum range of soil nail.
① Artificial fill, clayey soil and weak consolidated sand, which are above groundwater level or after artificial precipitation.
② General geotechnical medium and poor geological conditions as following: plastic clayey soil, sandy soil, breccia, soft soil and weathered rock formation, etc.
3. Unsuitable soil for traditional soil nail.
① Stratum with rich underground water. They will cause excavation face unstable and bonding force insecure.
② Low relative density and good degree of uniformity stratum but shortage of bonding force and too dry. They don’t have enough self -stable time and easy to collapse.
③ Expansive soil. After water penetrating, the load of soil nail increases and damage is easy to happen.
④ Soil with low strength, such as newly filled earth. They can’t provide enough anchoring force for soil nail and solidification will increase its load.
4. The advantages of self drilling anchor bolt as soil nail.
① Applying to all kinds of stratum and it has better effect in conventional technology but difficult to construct: silty soil and sandy soil.
② There is no limit for self drilling anchor bolt’s length. The routine length is 12-15 meters because of the limit of drilling equipment. But with little obstruction, self drilling anchor bolt can drill deeper and faster.
③ It can be constructed in small and narrow space. Overall thread is spread the surface of self drilling anchor bolt and it can be lengthened or cut arbitrarily.
④ Technological process is simple. Self drilling anchor bolt can do the work of drilling, grouting and anchoring at the same time, which is high efficient and cost-saving.
⑤ When grouting, slurry can be penetrated into tiny cracks of soil body. The grouting is fuller and safety factor is higher.
⑥ The impacting-rotary drilling likes the function of concrete vibrator, which makes slurry more dense and grouting effect better.