Closure to “Observed Performance of a Sheetpile-Supported Excavation in Chicago Clays” by Richard J. Finno, Sangrae Kim, Justin Lewis, and Nathan Van Winkle

Abstract

The writers thank the discusser for his interest in the paper and for the opportunity to expand on several items therein. The writers agree there are limitations with the Clough et al. (1989) method. When one looks at the scatter in the field data when plotted on the normalized movement versus system stiffness chart presented in Fig. 7 of Clough et al. (1989), it is clear that there are limitations inherent in the method if one is to use it to compute lateral wall movements during excavation. The authors included comparisons with the Clough et al. chart in the paper to place the performance of the excavation in context with other published data for excavations through clays. The discusser correctly identifies two of the major limitations, and the questions he posed related to these are addressed as following. Values for N c and Factor of Safety against Basal Heave Calculations The normalized lateral movements presented in the paper are those that developed only during excavation; those arising from sheet pile and caisson installation at the Robert H. Lurie Medical Research Center site and from sheetpile installation during sheet pile installation at the Louis A. Simpson and Kimberly K. Querry Biomedical Research Center (SQBRC) site were not included. The factor of safety (FS) was computed using Terzaghi's method (Terzaghi 1943). The depth of the failure surface below the excavation, D, was limited by either the Park Ridge or Hardpan strata, whichever resulted in the lowest FS against basal heave.