(1) The excavation methods for deep foundation pit projects mainly include sloped excavation, center-island (also called pier-type) excavation, basin-type excavation, and top-down (reverse) construction excavation. The first has no retaining structure, while the latter three all have retaining structures.
(2) The sequence and method of earthwork excavation must be consistent with the design conditions and follow the principles of "trenching with support, bracing before excavation, excavation in layers, and strict prohibition of over-excavation."
(3) Prevent excessive rebound deformation of the soil after excavation of deep foundation pits.
(4) Prevent slope instability.
(5) Prevent pile displacement and tilting.
(6) Coordinate with the construction of the deep foundation pit retaining structure.