Mainly manifested as excavation slope collapse, backfill compaction failing to meet requirements, foundation pit flooding, precast pile body fracture, excessive loose soil at the bottom of dry bored cast-in-place piles, and hole collapse in slurry wall-protected cast-in-place piles, along with their causes and preventive measures.
　　(1) Slope collapse
　　Causes: Insufficient slope gradient for foundation pit (trench) excavation, or improper sloping; when surface water or groundwater is present, effective dewatering and drainage measures are not taken, causing sand boils, mud boils, and water inflow; excessive surcharge loading at the top of the slope, or the influence of external vibration; soft soil, improper excavation sequence or methods, etc.
　　(2) Backfill compaction failing to meet requirements
　　Causes: Soil moisture content too high or too low; fill material not meeting requirements; insufficient energy of compaction or tamping equipment, failing to reach the required depth of influence, thereby reducing soil compaction.