Lateral load-deflection behaviour of single piles is often analysed in practice on the basis of methods of load-transfer P-Y curves. The paper is aimed at presenting the results of the interpretation of five full-scale horizontal loading tests of single instrumented piles in two sandy soils, in order to define the parameters of P-Y curves, namely the initial lateral reaction modulus and the lateral soil resistance, in correlation with the pressuremeter test parameters. P-Y curve parameters were found varying as a power of lateral pile/soil stiffness, on the basis of which hyperbolic P-Y curves in sand were proposed. The predictive capabilities of the proposed P-Y curves were assessed by predicting the soil/pile response in full-scale tests as well as in centrifuge tests and a very good agreement was found between the computed deflections and bending moments, and the measured ones. Small-sized database of fullscale pile loading tests in sand was built and a comparative study of some commonly used P-Y curve methods was undertaken. Moreover, it was shown that the load-deflection curves of these test piles may be normalised in a practical form for an approximate evaluation of pile deflection in a preliminary stage of pile design. At last, a parametric study undertaken on the basis of the proposed P-Y curves showed the significant influence of the lateral pile/soil stiffness on the nonlinear load-deflection response. Keywords Lateral loading test AE Lateral reaction modulus AE P-Y curves AE Pressuremeter test AE Sand AE Single pile List of symbols and units B diameter or frontal width of the pile (m) D embedded length of the pile (m) D e effective pile length (m) E elastic soil modulus (MPa) e excentricity of lateral load (m) E c characteristic soil modulus (MPa) E m first load pressuremeter modulus (MPa) E r reload pressuremeter modulus (MPa) E ti initial lateral reaction modulus (MPa) E p I p flexural pile stiffness (MN m 2 ) F tangential lateral reaction (kN/m) F l limit tangential lateral reaction or tangential lateral resistance (kN/m) G r pressuremeter shear modulus (G r = E r / [2(1 + m)]) (MPa) H lateral load applied on the pile top (kN) I d density index (%) K pile/soil compressibility K r lateral pile/soil stiffness L tangential dimension of the pile section (parallel to H) (m)
The paper presents lateralloading tests Onsingle piles in sand carri.edout on the LCPC centrifuge.The two models tested and the devices and instru.mentation are described. From the measured bending moments, the P-Y curves are derived and the subgrade reacrion modulus are compared with values from difjerenI methods (Menard, PHRl). The ejJect of a slope on the behaviour of larerally loaded pitt: was studied and results re/ated to ;".ead displacements and bending moments are presenIed.
This Note presents the results of axial loading tests carried out on an instrumented "pileprobe" jacked into sand, in a calibration chamber, aimed at studying the evolution of local friction, up to very large numbers of cycles (10 5 cycles). After an initial phase of friction degradation (cyclic softening), a subsequent phase of mobilized friction reinforcement (cyclic hardening) is observed, which continues to develop up to very large numbers of cycles. The complete mechanism of shear degradation followed by the reinforcement phase is interpreted based on the competition between two mechanisms which are the mean normal effective stress decrease due to cyclic contractancy phenomenon, responsible for cyclic softening, and the progressive densification of the sand within the interface zone around the probe, which becomes predominant after a certain number of cycles, resulting in a cyclic hardening mechanism due to partially constrained dilatancy phenomenon.
Centrifuge modelling and finite element analysis are powerful tools of research on the lateral pile/soil interaction. This paper aims at presenting the main results of experimental and numerical analysis of the pile response under monotonic lateral loading in sand. After description of the experimental devices, it focuses on the determination of the load-transfer P-Y curves for rigid and semi-rigid piles embedded in dry dense sand by using the experimental bending moment profiles obtained in centrifuge tests, as well as by a three-dimensional finite element models using ABAQUS Software. The elastic perfectly plastic Mohr-Coulomb constitutive model has been used to describe the soil response, and the surface-to-surface contact method of ABAQUS software has been used to take into account the nonlinear response at soil/pile interface. The analysis methodology has allowed to propose a hyperbolic function as a model to construct P-Y curves for rigid and semi-rigid piles embedded in dry dense sand, this model is governed by two main parameters, which are the initial subgrade reaction modulus, and the lateral soil resistance, the latter has been formulated in terms of Rankine’s passive earth pressure coefficient, the sand dry unit weight, and the pile diameter.
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