Karl Terzaghi and the Chicago Subway

Terzaghi's engagement on the Chicago Subway, 1939-1941, influenced his decision to take up permanent residence in the United States and had a strong impact on the development of applied soil mechanics. So-called squeeze tests, in which the settlements and subsurface movements were correlated with construction procedures, permitted improvements in construction methods and decreases in lost ground. Measurement of loads in bracing of open cuts led to better understanding of behavior of soft clay in undrained shear. Full-scale test sections provided basis for more economical design of permanent tunnel lining. All these activities evolved under Terzaghi's stimulation and in turn helped formulate his conceptions of the ways in which soil mechanics should be applied in practice.