What are the issues to be aware of in precipitation engineering?

1. Timing of Operations and Emergency Response Plan

Excavation of the foundation pit and dewatering operations should be scheduled during the season with minimal rainfall and low groundwater levels. By properly arranging the construction organization plan, the difficulty of dewatering can be minimized, and the construction compactness of the foundation structure at the bottom of the pit can be enhanced, allowing the structure to meet backfilling and flood prevention requirements as soon as possible, thereby shortening the duration of dewatering operations. To ensure construction compactness, an emergency response plan should be designed, including backup facilities and power supplies, rain protection and seepage prevention measures, slope stability, and settlement monitoring.

2. Layout of precipitation well points

The well points can be evenly distributed around the foundation pit. The absence of a well point due to the establishment of access roads to the foundation pit will not significantly impact the dewatering effect. However, for larger foundation pits, sometimes to ensure effective dewatering, it is necessary to set up some well points within the foundation pit. The distance between well point locations and the foundation pit perimeter is generally not less than 2 meters to ensure the stability of the pit slope.

Condition for stopping precipitation

It's not enough to stop dewatering just because the foundation pit's bottom structure is formed. Typically, one should consider whether the structure can be flooded or can be prevented from flooding, while also calculating the bottom plate strength and overall weight of the structure to ensure it can withstand and counteract the buoyant force caused by groundwater rise.

4. Groundwater Level Monitoring

During the precipitation process, it is essential to monitor groundwater levels to ensure they remain at a relatively stable elevation after prolonged rainfall, preventing excessive water level drop that could lead to resource wastage and uneven settlement of structures. Additionally, any abnormal rise or fall in groundwater levels should be promptly investigated to identify and eliminate potential hazards.

5. Uneven沉降

The uneven settlement of buildings around the foundation pit is primarily due to the decrease in groundwater levels. After the地基 foundation below the buildings desiccates, its load-bearing capacity is reduced, causing it to be compressed and consolidated under the action of gravity.