How do varying soil compositions influence the design and construction of deep foundation systems in civil engineering projects? Explore the implications of different soil types, such as cohesive and non$-$cohesive soils, on the selection of appropriate foundation types and construction techniques. Additionally, discuss the role of geotechnical investigations and soil testing in determining soil properties and their impact on foundation design. Consider the challenges posed by expansive soils, such as swelling and shrinking, and evaluate mitigation strategies to address these issues during construction and throughout the lifespan of the structure. Delve into the importance of considering factors like bearing capacity, settlement, and lateral stability when designing deep foundations in diverse soil conditions, and elucidate how engineers optimize foundation designs to ensure the structural integrity and stability of buildings, bridges, and other infrastructure projects.