Physical modeling is an established tool in geotechnical engineering for studying complex interaction problems involving soils. This chapter provides an overarching narrative of different aspects of such physical modeling include the challenging issue of designing meaningful (useful) tests and interpretation of the results for predicting prototype consequences. There are mainly two types of scaled physical modeling: (a) geotechnical centrifuge modeling under enhanced pseudo-gravity and (b) scaled modeling under 1-g, i.e., (Earth's gravity). Both approaches are briefly described together with the advantages and disadvantages. Furthermore, this chapter also discusses the two types of methods for designing and scaling model tests: (a) use of standard scaling laws available in textbooks which is “Black-box”-type modeling and (b) mechanics-based scaling. Few physical modeling examples (such as buckling instability of piles in liquefied soils, behavior of buried pipelines crossing faults and landslides, response of foundations for offshore wind turbines) are considered to show the mechanics-based scaling method. It has been shown that none of the techniques is perfect, and one needs the right tool for the right job. Black-box type modeling is suitable for simple interaction problems. However, for an unknown-unknown problem (typical of a multiple interaction problem), mechanics-based scaling method is appropriate. Do's and Don’ts in physical modeling are discussed.
