Deep excavation or construction of basements includes the construction of retaining walls, excavation, installation of struts, construction of foundations, floor slabs, and etc. Due to the variety of drilling methods and ancillary maintenance systems, in order to achieve the most suitable design, regional geological conditions, environmental conditions, authorized construction period, budget and existing construction facilities must be considered.

The most common excavation methods are completely open excavation, restrained excavation, island excavation, nailing and anchorage excavation, top-down construction, and regional drilling method.

Choosing the appropriate drilling method requires consideration of various factors such as construction budget, allowable construction period, adjacent excavations, availability of construction equipment, project site area, conditions of adjacent buildings, types of foundations of adjacent buildings, and etc. Expert engineers are able to make the right choices based on these factors.