t–z curves for piles from pressuremeter test results

Abstract

Pile design is not only based on the assessment of bearing capacity, but can involve settlement calculations when the structures supported by piles need high service requirements. In this context, the load transfer approach with t-z curve models is one of the calculation methods used. The main issue for this method is the choice and implementation of the t-z curve modelling the behaviour of the soil around the pile and accounting for the progressive shaft friction mobilisation. In this paper, three types of t-z curve models from pressuremeter test results are compared: one proposed previously by R. Frank and S. R. Zhao in 1982 and two others presented here. The stiffness of each model is studied and a comparison is performed by considering 90 full-scale static load tests extracted from the IFSTTAR pile database. Measured and calculated values of the pile head displacement are compared for several loading levels considering different soil and pile types. For the three t-z curve models, the ratio of the measured pile head settlement value to the calculated one is analysed and the scatter of each t-z curve model is studied. Some considerations regarding the safety of the pile settlement calculations are proposed.

Model Uncertainty in Predicting Facing Tensile Forces of Soil Nail Walls Using Bayesian Approach

“…The load terms, T and T n , are the same for the three facing limit states, as indicated by the performance functions (i.e., (1), (5), and (6)). This study is focused exclusively on the characterization of T for T n where T n is computed using the default and improved FHWA simplified facing tensile force models.…”

“…The quantification of model uncertainty can be done by characterizing the statistics of model bias which is the ratio of measured to nominal value of the variable of interest. Extensive studies on model uncertainty characterization for different geotechnical models have been reported in the literature, e.g., shallow and deep foundations [6][7][8][9][10][11] and retaining structures [12][13][14][15].…”

Some aspects of research and practice for pile design in France

“…It is interesting to note that the predictions made by Robas and Kuder [35] and by Said et al [36]-which are the closest predictions to the whole initial part of the measured load-settlement curve-both used the FrankZhao MPM method and were established entirely independently from the raw MPM readings. For categories 9-16, the above values are multiplied by 0.75 when the piles are vibro-driven instead of being driven Research on the use of t-z curves for the assessment of the settlements of piles using the full-scale results of the LCPC pile database has been developed further by Abchir et al [1] and Bohn et al [7].…”

Analysis of vertically loaded piles considering crushing characteristics of crushed stones

“…In past decades, a number of methods have been developed for pile response analysis, included the theoretical load transfer curve method [2–7], the shear displacement method [8–12], finite element method [13–16], the boundary-element method [17–20], the variational approach [21–24] and the field test [25–27], etc. It is worth mentioning that these studies reported that the pile was surrounded by clay, sand or rock-soil aggregate.…”