1. Project introduction.
Zipingpu Hydroelectric Station is located on the upper reaches of Minjiang River, Sichuan Province, about 9 kilometers away from Dujiangyan City, which is a comprehensive water conservancy project including irrigation, water supply, electricity generation, flood prevention, tourism and so on.
The total installed capacity is 4*190MW, annual electricity production is 34.7*108kw•h. The intake tower on the left is 80 meters high. It is a kind of weak and loose accumulation slope, which consists of soil, rocks and coal shale. The thickness of accumulation is 25 meters and it has high water content.
After excavation, deformation occurred and two cracks appeared on the surface of reviewing platform on the top of slope. Cracks continued before construction, which might damage the reviewing platform, even the whole project. After consideration, self-drilling anchor bolt was adopted for the slope stabilization.
2. Designing Schemes.
① Self-drilling anchor bar: adopting R32N type and 12 meters long rock bolt, while the distance is 4 meters and the dip angle is vertical with the slope. The grouting material is M30 cement paste, proportion of water and cement is 0.36:1. Because of the formation of slope, non-pressure grouting was adopted.
② Hanging net and shotcrete construction: steel bar with 6.5cm diameter was adopted, the size of net is 15cm*15cm. The thickness of shotcrete is 15cm and intensity is C20.
③ Drain pipe: the length is 8 m and distance is 3m. PVC floral tube was adopted and geotextiles were wrapped.
3. The processing of slope surface.
Artificial clean-up was adopted. Waste residue, plant cover and loose rocks were cleaned.
4. The construction of SDA bolt.
① Before installing self-drilling rock anchor, C20 concrete was jetted on the surface of slope, with 5cm thickness.
② For the loose and weak soil condition, falling of waste residue and deformation always happened, YT-28 air pick was used to put self drilling anchor bolt into drilled holes. The single bolt is 4m long and coupling was adopted to link two bolts.
③ Grouting: before grouting, air compressor was adopted to clean holes. Then certain proportion of water and cement was injected without interrupt, avoiding blocked.
④ The advantages of self drilling anchor bolt: for weak and loose slope condition, self drilling hollow anchor will increase the diameter of hole, enhance the intensity of soil and increase anti-corrosion effect. Slurry increases the bonding strength between anchor body and surrounding rocks, deformation capacity will be decreased accordingly.
Self-drilling anchor bolt: http://www.sdabolt.com/product/self-drilling-anchor-bolt/