Influence of cap beam restraint condition on the lateral deformation behavior of large-scale bored piles

Abstract

The restrained force at the pile cap plays an important role in assessing the stability of bored piles. The constraining force of the cap beam is difficult to calculate due to spatial variability in soil properties, nonlinear soil behavior, and measurement errors. Based on theoretical analysis and field measurements this study proposes an analytical model combining Bayesian theorem and Markov Chain Monte Carlo Simulations (MCMCS) to quantify the restrained force of a pile cap beam. A simplified mechanical model of the constrained effect of the cap beam is established and verified by the results of field measurements. Based on a field excavated slope project, a Bayesian updating modeling approach is established by combing prior information, empirical knowledge, field instrumentation results, and site investigations to calculate the constrained effects of the cap beam. To verify its effectiveness, the model is combined with a finite element model, taking into account the uncertainties of soil moduli and measurement errors. The modeling takes into account the spatial variability and strain dependence of Young’s modulus. By comparisons, it can be found that the predicted displacements of the support pile are in good agreement with the field measurements. The results show that a Bayesian back updating approach can reduce the impact of uncertainty that can guide geotechnical engineering design and construction of similar projects.