Modified Meyerhof approach for forecasting reliable ultimate capacity of the large diameter bored piles

Abstract

The static loading test is undoubtedly the most reliable method for forecasting the ultimate capacity of the large diameter bored piles (LDBP). However, in-situ loading of this class of piles until reaching failure is practically seldom due to the large amount of settlement required for shaft and base mobilization. Therefore, many international design standards recommend either capacity-based or settlement-based methods to estimate the LDBP ultimate capacity in case of the impossibility of performing loading tests during the design phase. However, those methods are invariably associated with various degrees of uncertainty resulting from several factors, as evidenced in several comparative analyses available in the literature. For instance, the settlement-based method of the Egyptian code of practice (ECP 202/4) usually underestimates the ultimate capacity of LDBP. In contrast, Meyerhof's capacity-based method often overestimates the LDBP’s ultimate capacity. In this paper, a modified approach has been proposed to forecast the ultimate capacity of the LDBP. This approach was modified from Meyerhof’s classical formula (1976) through three fundamental stages. First, an assessment study was performed to evaluate the reliability of the estimated LDBP ultimate capacity using Meyerhof’s classical method. For this purpose, results of full scale loaded to failure loading LDBP test and related twenty-eight parametric numerical models with various pile geometrical and soil geotechnical parameters have been used. Based on the assessment study findings, the essential modifications were suggested in the second stage to adapt Meyerhof’s classic method. In the third stage, the results of several numerical models and in-situ loading tests were employed to assess the accuracy of the developed modified method. This study showed that Meyerhof's classical method overestimated the ultimate capacity of LDBP with an error percentage ranging from 14 to 46%. On the other side, the proposed modified approach has succeeded in estimating the ultimate capacity of loaded to failure in-situ LDBP test and twenty numerical LDBP models with error percentages ranging from 0.267 to 7.75%.

A Novel Approach Proposal for Estimation of Ultimate Pile Bearing Capacity Based on Pile Loading Test Data

“…This method gives the highest correlation of all available SPT methods and is validated with soil data. Additionally, there are some methods in which the shear strength parameters of the soil are added to the calculation of the pile's ultimate bearing capacity by passing from the SPT values to the empirical relations [7][8][9][10][11][12][13].…”

Shallow foundation design: a comparative study of partial safety factors and full probabilistic methods

“…Not only the Czech engineering community has started start to realize this fact, and now we can see more projects dealing with this topic (see e.g. [17][18][19][20][21][22][23][24][25] ). The importance of fully probabilistic calculations lies in the rational and mathematically sound consideration of randomness and uncertainty due to a random and uncertain character of inputs to the model of a structure.…”