End Bearing Capacity Of Piles Research Articles

Liquefaction-induced settlement of the pile group under vertical and horizontal ground motions

End-bearing piles have been widely used to resist earthquake-induced settlement of buildings in sand deposits. However, the earthquake can generate the excess water pressure in saturated sand deposits and thus reduce both the friction resistance and end-bearing capacity of piles, further resulting in the pile settlement which may not be sustained by the superstructure. In this study, a fully coupled dynamic effective-stress finite element procedure is used to investigate the effects of the frequency content of input motion and the amplitude of both horizontal and vertical components of input motion on the settlement of the pile group in saturated sand deposits. A modified generalized plasticity model is employed to characterize the dynamic behavior of various density of sands. The effect of the soil permeability on the seismic response of the pile-soil system is investigated. The results indicate that the relatively distant earthquake cause more severe liquefaction at the sand deposit than the nearby earthquake and thus induces more settlement of the pile group under otherwise identical conditions. Moreover, the vertical ground motion could significantly increase the coseismic liquefaction-induced settlement of the pile group (ρE) and should be taken into account in engineering design. A simplified practical method based on the load-transfer methodology is proposed to estimate the ρE for the pile group with the cap above the ground.

Cavity Expansion–Contraction-Based Method for Tunnel–Soil–Pile Interaction in a Unified Clay and Sand Model: Drained Analysis

This paper proposes an analytical method based on drained solutions of cavity expansion and contraction in a unified clay and sand model to investigate tunnel–soil–pile interactions. Cavity expansion analyses are used to evaluate the effects of pile installation on ground stresses and to determine pile end-bearing capacity and the distribution of shaft friction. Cavity contraction methods were adopted to replicate the tunnel convergence–confinement response using the singularity and image method for ground loss and ovalization of a shallow tunnel in a semi-infinite medium. A 2D model was developed that evaluates changes in mean stress and specific volume during pile installation and tunnel excavation. Outcomes from the developed analytical approach are compared against data from centrifuge tests in silica sand; results demonstrate that trends in pile load capacity degradation, mobilized safety factor, and tunneling-induced pile settlement can be satisfactorily predicted for the case of a tunnel excavated beneath a pile with a constant service load. Criteria based on pile capacity, safety factor, and settlement are proposed that can be used to determine a critical tunnel volume loss or evaluate pile safety level. The paper contributes to the understanding of tunnel–soil–structure interaction mechanisms and provides an efficient means of conducting a preliminary risk assessment of tunnel–pile interaction.

Further Debate about Visual Design Methods for Pile Foundation

The computing of end-bearing capacity of pile has vital significances for foundation design while the foundations analysis is usually problematic due to those diverse soils and engineering conditions. Though various CPT-based methods which have already been applied in numerous huge engineering practices are available for the analysis of pile foundation bearing capacity home and abroad, there still seemed lacking legitimate guidance assisting to select these formulations quite effectively. In this paper, five CPT-based design methods are compared in deep, the realization through computer program is also presented, with the capacity data accumulated from pile engineering coming into mind, we are on the way to making designers choose better methods during the designing process.

Tunnel-Pile Interaction Analysis Using Cavity Expansion Methods

AbstractEvaluation of the impact of tunnel construction on existing buried structures is an important problem. This paper presents an analytical method for estimating the effect of tunnel construction on end-bearing piles located above the tunnel. The method can be used to estimate the safe relative distance between existing piles and newly constructed tunnels. Spherical and cylindrical cavity expansion/contraction analyses are used to evaluate pile end-bearing capacity and the reduction of confining pressure at the pile tip that results from tunnel volume loss. Pile end-bearing capacity is then reevaluated based on the reduced confining pressure at the pile tip. A modified shear modulus is used to account for the effect of pile installation on soil stiffness. The method is used to analyze centrifuge experiments conducted to study this problem. For the experimental data, where the service load applied to the piles during tunnel volume loss ranged between 50 and 60% of the maximum jacking force, the analyt...

Pile End-Bearing Capacity of Sand Related to Soil Compressibility

A simple method based on theoretical and experimental considerations is presented to predict the pile end bearing capacity and load-settlement curve in sands in relation to soil compressibility. The key to the method is in the assumption of a failure mode with a spherical cavity expansion pressure given as a function of the soil compressibility, shear stiffness and friction angle. The practical prediction of pile end-bearing capacity in sandy ground is discussed in terms of a compressibility factor, friction angle and shear stiffness. Further, the pile tip settlement behaviour is also discussed based on an empirical model incorporating the pile end bearing capacity from a cavity expansion analysis with a Kondner type hyperbolic function. The applicability of the proposed method is verified by comparing the predicted results with the results from a series of model pile load tests and a database for in-situ pile load tests in sands.

Pile end-bearing capacity in crushable sands : N. Yasufuku & A. F. L. Hyde, Geotechnique, 45(4), 1995, pp 663–676

Pile end-bearing capacity in crushable sands : N. Yasufuku & A. F. L. Hyde, Geotechnique, 45(4), 1995, pp 663–676

Pile end-bearing capacity in crushable sands

The occurrence and formation of crushable soils is a widespread phenomenon. Warm tropical seas give rise to deep deposits of biogenic skeletal sediments in coastal shelf areas, or exposed granitic intrusions are subjected to deep weathering resulting in decomposition. The end-bearing capacity of piles in crushable soils is important for the design of foundations in these diverse soils, but the analysis of foundations in these soils is problematic due to their compressibility and highly curved Mohr–Coulomb failure envelopes. The use of the spherical cavity expansion method offers potential for a better prediction of end-bearing capacities by taking into account soil crushability and the decrease of friction angle with increasing mean normal stress. A formula relating end-bearing pressure to the pressure to expand a cavity and the soil secant friction angle has been developed, which refines and simplifies Vesic's original equations. However, the actual model pile settlement ratio at which the predicted cavity expansion values were reached increased with soil crushability and decreased with increasing relative density. A simple linear relationship has been proposed between a soil compressibility index Cp and the pile settlement ratio at which the bearing capacity predicted by the theoretical cavity expansion method is mobilized. KEYWORDS: calcareous soils: laboratory tests; model tests; offshore engineering; piles; sands. Les sols compressibles sont des formations très répandues. Its se forment dans les mers chaudes tropicales qui favorisent le dépôt de sédiments biogéniques profonds dans les zones de plate-forme côtière, ou proviennent de l'altération profonde de granites intrusifs affleurants se traduisant par une décomposition du matériau. La capacité portante en pointe des pieux devient done un paramètre primordial pour la conception de fondations dans ce type de sols. Toute analyse de fondations dans ce type de sols pose cependant des problèmes en raison de la compressibilité et des enveloppes de rupture de Mohr–Coulomb très incurvées de ces sols. La méthode par expansion d'une cavité sphérique est susceptible de permettre une meilleure prévision de la capacité portane en pointe puisqu'elle prend en compte la compressibilité du sol et al diminution de l'angle de frottement lorsque la contrainte normale moyenne augmente. Une équation, plus simple que les équations de Vesic, a été établie entre la pression en pointe, la pression d'expansion d'une cavité et l'angle de frottement tangential du sol. Cependent, avec notre modèle de pieux actuel, les valeurs de tassement, correspondant aux valeurs prévisionnelles de l'essai d'expansion de cavité, augmentent avec la compressibilité du sol et diminuent lorsque la densité relative augmente. On propose une relation linéaire simple entre l'indice de compressibilité Cpdu sol et le tassement des pieux pour lequel la capacité portante prevue par la méthode d'expansion d'une cavité théorique est mobilisée.

End bearing capacity of piles in calcareous sands : Golightly, C R; Nauroy, J F Proc 22nd Annual Offshore Technology Conference, Houston,7–10 May, 1990 V1, P345–356, Publ Richardson: OTC, 1990

End bearing capacity of piles in calcareous sands : Golightly, C R; Nauroy, J F Proc 22nd Annual Offshore Technology Conference, Houston,7–10 May, 1990 V1, P345–356, Publ Richardson: OTC, 1990