Lessons learned from case studies of excavation support systems through Chicago glacial clays

This paper summarizes the lessons learned from three detailed case studies of supported excavations made through soft to medium glacial clays. In particular, the use of inverse analysis techniques with finite element simulations are shown to be an effect way to calibrate soil parameters, if sufficient detail is included in the numerical simulation of the excavation. The large effect of past construction activities at an urban site on computed displacements is illustrated by results from all three excavations. Previous tunneling operations, building construction, site grading and wall installation affects the stresses that exist in the ground just prior to start of excavation. Not properly accounting for these factors results in either numerical results that do not match field observations or if a reasonable match does result, then the soil parameters are not representative of the natural soils. Furthermore, the combined use of lateral movements and forces in internal bracing are shown to provide a higher sensitivity to the observations that either type of measurement alone.