When it comes to the construction of a structure and its long term safety and durability, deep foundations and support of excavation may be needed. Each is its own unique system that requires extensive monitoring and a high level of engineering skill and expertise.


When existing soil is not stable enough to handle a shallow foundation, a deep foundation is used. This type of foundation transfers building loads to the soil farther down than a shallow foundation does to a subsurface layer more stable.

The main role of deep foundations is to transmit the weight of the building to the firm layers deep below grade, bypassing weaker subsurface layers.

Some common reasons for deep foundations include:

  • Large design loads
  • Poor soil at the shallow depth – organics, uncontrolled fill 
  • Site constraints such as property lines


During the construction process, excavation is often required to remove earth, rock, or other materials. This process is widely used in construction to create building foundations, roads, and more.

Certain projects need support of excavation in order to reach the required construction depths. Areas with property line constraints or limits on sloping back the excavation require temporary earth retention structures to be built. These earth retaining structures are generally used for deep excavations that exceed a depth of six feet. 

Examples of excavation support systems include soldier piles & lagging, steel sheet piles with tiebacks, braced walls with internal steel struts / rakers, slurry walls, etc. 

The safety and soundness of your construction project require highly skilled structural engineers that have experience in both deep foundation and excavation support. Connolly Engineering has innovative engineering solutions for all your construction needs. Contact us today to discuss your next project!