The general stratum subsidence can be said to be a natural phenomenon. The alluvial plain formed by the sand and rock alluvial from the river, the smaller the sand and rock particles, the more obvious the degree of compaction. This is a natural stratum subsidence. When external forces, such as vehicle vibration, construction vibration, and building weight, will compact the ground, this is the second type of ground subsidence that cannot be avoided. Excessive pumping of groundwater can also cause stratum subsidence, which is man-made damage. Because there will be some underground water in the soil, these water molecules will have water pressure, so they will support the soil. When we super pump the groundwater, the water between the soil particles is gone, and only air is left. The air is easily squeezed out, which will cause the soil to shrink, that is, the ground that we see on the surface sinks.

The main causes of stratum subsidence can be roughly summarized as follows:

(1) Excessive pumping of groundwater-reduction of bearing stress, resulting in site subsidence.

(2) The groundwater level drops-the carrying load increases, resulting in soil compaction.

(3) Ground structures-due to the construction of tall buildings, the load-bearing load increases.

(4) Earthquake-Sandy soil has subsided due to earthquake.

(5) Excavation and mining of deep foundations-cause the site to move and cause the ground to sink.

(6) Shallow covering excavation-shallow covering excavation for tunnels, culverts, pipeline facilities, etc.

(7) The rising or sinking phenomenon of the site itself.