An analytical method for developing a theoretical load-settlement curve for axially loaded piles in clay is presented. The method is based on the correlation of the ratio of load transfer to soil shear strength as a function of pile movement. The results of studies of field tests of instrumented piles and laboratory tests of small piles in clay are used to obtain the desired correlation. The correlation is presented in the form of a family of curves that are obtained when the ratios of load transfer to soil shear strength versus pile movement are plotted as a function of depth. The validity of the family of correlation curves is checked by comparing computed and actual load-settlement curves for some typical field tests. Results obtained by this method indicate that the method may be used effectively to determine load-carrying capacity for axially loaded piles in clay.

Closure to “Load Transfer for Axially Loaded Piles in Clay”

Current seismic design of bridges is based on a displacement performance philosophy using nonlinear static pushover analysis. This type of bridge design necessitates that the geotechnical engineer predict the resistance of the abutment backfill soils, which is inherently nonlinear with respect to the displacement between soil backfill and the bridge structure. This paper employs limit-equilibrium methods using mobilized logarithmic-spiral failure surfaces coupled with a modified hyperbolic soil stress-strain behavior (LSH model) to estimate abutment nonlinear force-displacement capacity as a function of wall displacement and soil backfill properties. The calculated force-displacement capacity is validated against the results from eight field experiments conducted on various typical structure backfills. Using LSH and experimental data, a simple hyperbolic force-displacement (HFD) equation is developed that can provide the same results using only the backfill soil stiffness and ultimate soil capacity. HFD is compatible with current CALTRANS practice in regard to the seismic design of bridge abutments. The LSH and HFD models are powerful and effective tools for practicing engineers to produce realistic bridge response for performance-based bridge design.

Nonlinear Soil-Abutment-Bridge Structure Interaction for Seismic Performance-Based Design

An elastic analysis is presented for the horizontal displacement and rotation of a laterally loaded pile group and the distribution of horizontal forces within the group. The interaction between two identical equally loaded piles is analyzed first, and the increases in displacement and rotation of the piles, in relation to the single pile values, are expressed in terms of interaction factors. Using these interaction factors, a method for calculating the displacement and rotation of a general pile group, based on the principle of superposition, is described. An examination of the behavior of square groups of piles reveals that the displacement, rotation, and load distribution in the group is largely influenced by the length-to-diameter ratio of the piles and the relative pile flexibility. It is also found that the displacement depends on the breadth of the group rather than the number of piles in the group. A reasonable measure of agreement is found between a limited number of reported measurements and theoretical predictions of group displacements.

Closure to “Behavior of Laterally Loaded Piles: II-Pile Groups”

Although most designers prefer the p-y curve method as compared to elastic continuum or finite-element analysis of laterally loaded pile behavior, the profession has reached a state where it is tim...

Modeling lateral soil-pile response based on soil-pile interaction

Analysis of soil resistance on laterally loaded piles based on 3D soil–pile interaction

Beam on elastic foundation theory provides an efficient solution for the problem of a laterally loaded pile. The accuracy of such a solution depends upon the characterization of the interaction between the pile and the surrounding soil. A particularly good representation of the soil-pile interaction yields a more realistic solution. While traditional nonlinear "p-y" characterization provides reasonable assessment for a wide range of loaded piles, it has been found that the p-y curve (or the modulus of subgrade reaction) depends on pile properties (width, shape, bending stiffness, and pile-head conditions) as well as soil properties. The strain wedge model allows the assessment of the nonlinear p-y curve response of a laterally loaded pile based on the envisioned relationship between the three-dimensional response of a flexible pile in the soil to its one-dimensional beam on elastic foundation parameters. In addition, the strain wedge model employs stress-strain-strength behavior of the soil as established from the triaxial test and the effective stress condition to evaluate the mobilized soil behavior.

Lateral loading of a pile in layered soil using the strain wedge model

Analysis of pile stabilized slopes based on soil–pile interaction

Assessment of the response of a laterally loaded pile group based on soilpile interaction is presented in this paper The behavior of a pile group in uniform and layered soil (sand and/or clay) is 

Lateral Behavior of Pile Groups in Layered Soils

Formulation of the mobilized force-displacement-capacity for the seismic design of a bridge abutment–embankment system is presented herein. As part of the seismic design philosophy of bridge structures, a realistic prediction of the abutment–embankment participation should be included in the bridge demand and capacity assessments. The nonlinear force-displacement capacity and/or stiffness of a bridge abutment–embankment system is a function of the abutment height, embankment soil properties (mobilized soil resistance), and the mobilized interface friction angle between the embankment and bridge abutment. A method based on a limit equilibrium logarithmic spiral, method of slices, coupled with characterization of the stress-strain behavior of the soil is employed. The stress-strain characterization relies on standard triaxial test results. The use of Mohr–Coulomb strength criteria based on mobilized strength parameters allows the consideration of a developing mobilized surface via limit equilibrium. The str...

Mohamed Ashour

Papers

Lateral loading of a pile in layered soil using the strain wedge model

Modeling lateral soil-pile response based on soil-pile interaction

Analysis of pile stabilized slopes based on soil–pile interaction

Lateral Behavior of Pile Groups in Layered Soils

Bridge Abutment Nonlinear Force-Displacement-Capacity Prediction for Seismic Design