Piles In Cohesionless Soils Research Articles

Inelastic Seismic Response of Bridge Drilled-Shaft RC Pile/Columns

An analytical model based on a Winkler beam is used to represent the lateral force response of a reinforced concrete (RC) pile in cohesionless soil. An inelastic finite-element analysis was performed on the structure, using as the pile constitutive model the section moment-curvature relationship based on confined stress-strain relationships for the concrete. Parameters varied were pile head restraint (free and fixed head), height of pile head above grade level, and soil stiffness. Linear, bilinear, and hyperbolic soil models were examined. The analysis showed that shear would be significantly underpredicted by an elastic analysis, as inelastic behavior moved the point of maximum moment in the pile shaft closer to the surface, thus reducing the shear span. Maximum moment depth in the pile shaft and plastic hinge length were also shown to be strongly dependent on soil stiffness, and in the case of fixed-head piles, on abovegrade height of the superstructure. Linear soil models were shown to be adequate for most cases of pile/column design.

Experimental study of axial behaviour of tapered piles: Reply

Experimental study of axial behaviour of tapered piles: Reply

Response of tapered piles subjected to lateral loading

Eighteen lateral loading tests were conducted on large-scale steel piles to establish the lateral behaviour of tapered piles in cohesionless soil. Three piles 1.52 m in length with different taper angles but the same average embedded diameter of 168 mm were installed in sand enclosed in a steel chamber 1.5 m in diameter and 1.445 m in depth. The soil chamber was lined with an air bladder so that sand inside the chamber could be pressurized to vary the confining pressure. The piles were instrumented with electrical resistance strain gauges and the horizontal pile movements at grade and the loading point were measured with displacement transducers. The bending-moment functions along the pile were calculated from the strain measurements by curve fitting the measured strain data. The soil resistance (p) and pile displacement (y) relationships were developed in the form of p-y curves by differentiating and integrating these bending-moment functions. It was found that tapered piles carried up to 77% more lateral loads than straight-sided-wall piles with the same average diameter. The maximum bending moment occurred in all piles at almost the same depth of one third of the embedded length of the pile. Hence, the cross section of tapered piles at the location of maximum bending moment was larger than that of straight-sided-wall piles, resulting in lower stresses in the pile. It was concluded that the tapered piles represent a more efficient distribution of the pile material and display better performance under lateral loading conditions.Key words: tapered piles, lateral response, p-y curves, modulus of subgrade reaction.

Lateral Capacity of Model Rigid Piles in Cohesionless Soils

The analysis and computation of the ultimate lateral capacity of rigid piles is usually based on a simplified soil pressure distribution along the pile length. Actual soil pressure distributions were measured in a rigid model pile along its length and across the diameter and it was found that the simplified theoretical assumptions of pressure distribution needs a modification. A method is suggested in this paper to predict soil pressure distribution and ultimate lateral capacity for rigid piles in cohesionless soils. Field and laboratory data from published literature are used to validate the proposed method.

General Regression Neural Networks for Driven Piles in Cohesionless Soils

Numerous investigations have been conducted in recent years to predict the load-bearing capacity of driven piles in cohesionless soils. The problem is extremely complex owing to the large number of factors that affect the behavior of piles. The available methods either oversimplify the nature of the problem or improperly consider the effect of certain governing factors. In this paper, a general regression neural network (GRNN) is used for predicting the capacity of driven piles in cohesionless soils. Predictions of the tip, shaft, and total pile capacities are made for piles with available corresponding measurements of such values. This is done using four different procedures as well as the GRNN. Comparisons of capacity component predictions (i.e., tip and shaft capacities) are achieved only for instrumented piles. The actual measurements of tip and shaft pile capacities were adjusted to account for residual stress using the wave equation analysis. For the remaining piles, the predicted total capacities are compared only with the measured values. The GRNN provides the best predictions for the pile capacity and its components. It is also shown that the GRNN is applicable for all types of conditions of driven piles in cohesionless soils.

Centrifugal testing of laterally loaded piles in sand

Results of an investigation of the response of piles in sand, under lateral loads, are presented. Model piles of three different diameters and flexural stiffnesses were tested in a centrifuge apparatus to determine prototype pile behavior. The experimental results, consisting of pile head displacements and bending moment distributions along the pile length, were interpreted, analyzed, and compared with the results of several numerical analyses. The piles were treated as elastic beams on nonlinear springs, examining several different types of soil reaction relationship (p-y curves). A new p-y relationship was developed for piles in cohesionless soil which provided very satisfactory results. Key words : pile, sand, lateral loading, centrifuge, numerical analysis.

Model for Capacity of Single Piles in Sand Using Fuzzy Sets

Prediction of load-carrying capacity of piles in cohesionless soils has been and is still one of the most challenging problems facing geotechnical engineers. The problem is complex and difficult due to the lack of understanding of the phenomena of soil-pile interaction, and the limited quantity and inexact quality of subsurface soil information that can be provided for analysis. Current methods of estimating pile capacity have uncertainties that are not accounted for, including uncertainties in the method and in the data used to execute the method. Many of these uncertainties defy conventional quantification. The application of fuzzy-set theory, which can assist in accounting for these uncertainties, is offered as a solution. A model based on the theory of fuzzy sets that estimates ultimate capacity of single piles in sand is presented. Uncertainties associated with both input data and predicting methods are accounted for. In particular, qualitative information and subjective judgment are incorporated in the computations. A computer program that adopts the proposed model yields improved prediction of ultimate capacity for the cases studied.

Nonlinear analysis of laterally loaded piles in cohesionless soils : Budhu, M; Davies, T G Can Geotech JV24, N2, May 1987, P289–296

Nonlinear analysis of laterally loaded piles in cohesionless soils : Budhu, M; Davies, T G Can Geotech JV24, N2, May 1987, P289–296

Nonlinear analysis of laterally loaded piles in cohesionless soils : Budhu, M; Davies, T G Can Geotech JV24, N2, May 1987, P289–296

Nonlinear analysis of laterally loaded piles in cohesionless soils : Budhu, M; Davies, T G Can Geotech JV24, N2, May 1987, P289–296

Load‐Deformation Response of Axially Loaded Piles

A new empirical scheme for simulating the nonlinear point resistance response of single piles in cohesionless soils is proposed. The pile‐soil system is idealized by using a one‐dimensional finite element technique. The shear resistance response along the pile shaft is found by using the concept of t‐z curve proposed by Kraft et al., whereas the new method is used to define the tip resistance response or the so‐called p‐z curve. A generalized Ramberg‐Osgood model is utilized to simulate the nonlinear t‐z and p‐z curves. To check the validity of the method, four examples involving field and laboratory tests on piles in sands are considered. The comparisons between the finite element predictions, and the laboratory and field observations, show good correlation. The results are relevant to a specific class of problems that involve submerged or dry sand, long piles, and a constant value of the lateral earth pressure coefficient.

Nonlinear analysis of laterality loaded piles in cohesionless soils

The results of a numerical analysis of single laterally loaded piles embedded in cohesionless soils, taking soil yielding into account, are presented. The analysis is intended to serve as an independent alternative to the well-known p–y method. The input parameters for the soil are the angle of internal friction and a parameter characterizing the increase in soil stiffness with depth, here assumed to be linear. A parametric study shows that soil yielding significantly increases the maximum pile bending moments and lateral displacements. Equations suitable for routine design applications are presented and the ease with which these can be applied in practice is demonstrated by an illustrative example. Good agreement between the theoretical results and data from published case histories attests to the validity of the method. Key words: analysis, angle of friction, cohesionless, deformation, design, failure, foundations, piles, lateral, loads.

Comprehensive investigations of horizontally loaded piles in cohesionless soils

down to 10% at near-critical loads, i.e., friction forces along the side surfaces come into full operation before the limiting state is reached, and in the early stages of loading greatly affect the total reactive resistance. However, these conclusions require refinement because in the tests, the intensity of contact pressures was measured only at the middle of the pile width, and the distribution of the soil reaction over its width was assumed to be uniform; furthermore, no investigations at all were made of the intensities of the friction forces. Meanwhile, Baguelin and Jezequel [5] had established on the basis of thorough tests that, at large displacements, the soil-reaction pressure at the center of a plane surface of a pile is 30% greater than at its edges. From this it is obvious that account must be taken of the characteristic features of the reactive-pressure distribution along the contact surface, in order to reliably determine the average reactive pressure of the soil where large displacements are involved. Where cylindrical piles are under investigation, the problem becomes even more complex; and in order to determine the average soil-reaction pressure over the pile perimeter, one has to install 3-5, or even a greater number, of soil dynamometers. As has already been remarked above, the p vs u relationship is nonlinear; therefore, the variable modulus of subgrade reaction or, as it is more aptly named-modulus of horizontal soil resistance K is a function of depth z and displacement u. If the function K = f(u, z) is known, then the problem of the bending of a pile subjected to external force factors can be solved by an electronic computer. The quantitative description of modulus K is best realized by a family of p--u graphs plotted to give the soil reaction pressure p as a function of pile displacement u for each of the design sections along the pile depth [6]. The results of tests during which measurements are taken of all the soil-reaction components and pile displacements at various depths, enable K(u, z) to be determined in the most definite and reliable manner.

Numerical design-analysis for piles in sands

A number of field load tests for piles in cohesionless soils are analyzed using the finite element method. Satisfactory correlations are obtained between numerical predictions and observations for pile movements versus applied load, and division of total load into point and skin friction components. Computed bearing capacities using various failure criteria show good agreement with those evaluated from a formula based on limit equilibrium and from field data. Distributions of normal and shear stresses along the pile wall, and coefficient of lateral earth pressure, and significance of stress paths in the stress-strain law are examined. Effects of diameter and length of embedment on bearing capacity, particularly at higher lengths of embedments, are found to differ from those given by the limit equilibrium formula. A modification in the formula is suggested to account for the reduction in bearing capacity with length of embedment.

Numerical Design-Analysis for Piles in Sands

A number of field load tests for piles in cohesionless soils are analyzed using the finite element method. Satisfactory correlations are obtained between numerical predictions and observations for pile movements versus applied load, and division of total load into point and skin friction components. Computed bearing capacities using various failure criteria show good agreement with those evaluated from a formula based on limit equilibrium and from field data. Distributions of normal and shear stresses along the pile wall, and coefficient of lateral earth pressure, and significance of stress paths in the stress-strain law are examined. Effects of diameter and length of embedment on bearing capacity, particularly at higher lengths of embedments, are found to differ from those given by the limit equilibrium formula. A modification in the formula is suggested to account for the reduction in bearing capacity with length of embedment.

Pile tests at Beech River

A program of pile loading tests has been carried out by the D.H.O. Foundation Section, at the site of the proposed new bridge over Beech River on Hwy. 35 near Carnarvon, Ontario. Subsoil consists of deep deposits of sands and silts. Five piles of various lengths were tested to failure, these being [Formula: see text]. O.D. (32.4 cm) steel tubes, 12 BP 53 steel H-piles, and one No. 14 timber pile.The results of the tests have been compared with predictions based on theoretical and empirical conventional methods and, also, by a method using information obtained in the field using the Geoprobe. The results of the load tests illustrate clearly the difficulties involved in attempting to assess loading capacities of piles in cohesionless soils by means of the conventional methods based on soil properties determined during routine foundation investigations.

Closure to “Lateral Resistance of Piles in Cohesionless Soils”

Closure to “Lateral Resistance of Piles in Cohesionless Soils”

Discussion of “Lateral Resistance of Piles in Cohesionless Soils”

Discussion of “Lateral Resistance of Piles in Cohesionless Soils”

Closure to “Bearing Capacity of Piles in Cohesionless Soils”

Closure to “Bearing Capacity of Piles in Cohesionless Soils”

Lateral Resistance of Piles in Cohesionless Soils

Methods are presented for the calculation of deflections, ultimate resistance, and moment distribution for laterally loaded single piles and pile groups driven into cohesionless soils. The lateral deflections have been calculated assuming that the coefficient of subgrade reaction increases linearly with depth and that the value of this coefficient depends primarily on the relative density of the supporting soil. The ultimate lateral resistance has been assumed to be governed by the yield or ultimate moment resistance of the pile section or by the ultimate lateral resistance of the supporting soil. The ultimate lateral resistance is assumed to be equal to three times the passive Rankine earth pressure. The deflections and lateral resistance, as calculated by the proposed methods, have been compared with available test data. Satisfactory agreement was found.

Lateral Resistance of Piles in Cohesionless Soils

Lateral Resistance of Piles in Cohesionless Soils