Grouted Tieback Anchor for Deep Foundation Pit

In the deep foundation pit construction of Qiangdao subway Shuangshan station, the following problems existed in the construction of cable bolt system:
1. Due to the complex geological conditions, rock fracture formed and developed. In the process of drilling, the air leakage phenomenon was serious, resulting that the rock flour was unable to be blown out of the hole, which often caused sticking. Once stuck, it was unable to drill any more, resulting wasting time and delaying construction period and causing the scrap of the cable bolt if not handled properly.
2. Holes were easy to collapse and the adjacent holes were easy to be strung together, which led to the difficulty to insert cable bolt.
3. Poor geological condition, much rock fracture and rich ground water resulted that the cable bolt grouting was not full.

In view of the above situation, the contractor finally decided to use grouted tieback anchor instead of cable bolt for the slope support. Grouted tieback anchor integrates drilling, installing, grouting and anchoring in one operation. It has the advantages of fast construction speed, large anchoring force, good corrosion resistance, light weight, simple operation, timely provision of anchoring force and adaptability for hole formation.

The application of grouted tieback anchor successfully solved the technical difficulty of hole formation in the broken rock mass of Qingdao Subway Shuangshan station retaining structure, ensured the safety of the foundation pit, guaranteed the schedule of the subway construction and achieved good social benefit. The engineering practice has proved that grouted tieback anchor is a reliable anchorage technology, and has a wide range of application prospect.