Bootstrapping for Characterizing the Effect of Uncertainty in Sample Statistics for Braced Excavations

Abstract

A simple procedure for assessing the probability of serviceability failure in a braced excavation involving bootstrapping to char- acterize the effect of uncertainty in sample statistics is presented. Here, the failure is defined when an excavation system's response in terms of themaximumwalldeflectionorgroundsettlementthatexceedsthelimitingvaluespecifiedbytheclientorinanapplicablecode.Theanalysisfor the probability of failure (or probability of exceedance) necessitates an evaluation of the means and SDs of critical soil parameters. In geotechnical practice,thesemeansandSDsareoftenestimatedfromaverylimiteddataset,whichcanleadtouncertaintyinthederivedsample statistics. Thus, in this study bootstrapping is used to characterize the uncertainty or variation of sample statistics and its effect on the failure probability.Throughthebootstrappinganalysis,theprobabilityofexceedancecanbepresentedasaconfidenceintervalinsteadofasingle, fixed probability.Theinformationgainedshouldenabletheengineertomakeamorerationalassessmentoftheriskofserviceabilityfailureinabraced excavation. The study points to the potential of the bootstrap method in coping with the problem of having to evaluate failure probability with uncertain sample statistics. DOI: 10.1061/(ASCE)GT.1943-5606.0000734. © 2013 American Society of Civil Engineers. CE Database subject headings: Excavation; Bracing; Serviceability; Probability distribution; Parameters; Uncertainty principles; Statistics. Author keywords: Probability distribution; Parameter uncertainty; Sample statistics; Bootstrapping; excavation; Ground settlement; Wall deflection.