The upstream intake tower of Zipingpu Hydropower Station is 80m in height. The slope is loose accumulation after excavation, mainly composed of soil, rock and coal shale. The loose accumulation is 25m in thickness with much water in slope. The slope deformed and formed two cracks after excavation, which was likely to endanger the safety of the balcony and the intake tower construction. According to the designers, the slope was supported by SDA bolt for grouting and hanging net shotcrete.
The project determined to use R32N SDA bolt. In view of the loose accumulation slope, the project adopted no pressure grouting design. That is, when the liquid evenly returns around the orifice evenly, the grouting can be finished.
The project used QZJ100 DTH drill for drilling holes. Because of the soft and broken surrounding rocks, the hole wall deformed easily after drilling. Therefore, YT-28 pneumatic pick was immediately used for picking SDA bolt into the hole. The whole length of SDA bolt is 12.0m and each SDA bolt is 4.0m connected together by couplers. It’s hard to make hole for the common method in the loose accumulation, so the contractor adopted effective measures to overcome this problem by discharging once drilling 30cm in soft stratum. Moreover, the wind pressure of the drilling machine is guaranteed in the process of drilling. Blowing out most of water and then continue to drill when encountered much water in the hole. The drilling accident was avoided and the drilling efficiency was improved by taking this measure.
The slope strength has been changed by SDA bolt, and the problem of loose rock slope deformation has been successfully solved. The construction method of combining SDA bolt with hanging net shotcrete is a successful slope treatment measure. The construction speed is fast, safe and reliable. It is well worth popularizing and applying in other loose rock slope support.