Uncertain Geotechnical Truth and Cost Effective High-Rise Foundation Design

Uncertain geotechnical truth affects our ability to produce cost effective high rise foundation design. Virtually no amount of subsurface exploration and laboratory testing can ever provide the complete geotechnical truth. However, structural engineers and geotechnical engineers working as a team balance the available knowledge, including site geology and performance prediction history using in-situ empirically developed geotechnical parameters, with the level of acceptable risk and cost. A brief history of the author's Chicago experience and development with the Menard pressuremeter for in-situ testing is presented. Advice to follow for best results is outlined together with case histories to illustrate the following: (1) Maximizing allowable bearing pressure; (2) Use of mixed foundation systems; (3) Use of highly stressed piles for settlement reduction; (4) Reuse of existing foundations; (5) Construction surprises requiring remediation