After the strength of the supporting pile reaches the design strength, earthwork excavation can be carried out (generally after 28 days of concrete curing). In addition, the pouring period of 188 root must be 2 months, so it can be cross-constructed. The pre-cast area can be excavated, but the strength of the pile must be guaranteed.

Foundation pit classification

Grade I: the foundation pit has important engineering or supporting structure as a part of the main structure, and the excavation depth is greater than10m, and the distance from adjacent buildings and important facilities is within the excavation depth. There are foundation pits with historical relics, excellent modern buildings and important pipelines. Need strict protection.

Grade II: Foundation pit between Grade I and Grade III.

Grade III: Foundation pit with excavation depth less than 7m and no special requirements for surrounding environment.