Settlement analysis of friction piles in consolidating soft soils

Reliable prediction of settlement behaviour of axially loaded piles is one of the major concerns in geotechnical engineering. Therefore, this paper focuses on the finite element solutions of load-settlement behaviour of a single pile and pile group using PLAXIS numerical package. Three different types of analysis were incorporated: a linear elastic analysis, a complete nonlinear analysis and a combined analysis. The pile case history with settlement measurements made during field pile load test was considered to validate the single pile load-settlement simulation, and the same load test result was extended to simulate the load-settlement behaviour of pile group using RATZ analytical approach. The single pile analysis results suggest that realistic load-settlement predictions can be drawn by considering complete soil as Mohr-Coulomb model at lower working loads, and incorporation of an interface zone thickness of two times pile diameter using Hardening-Soil model is required to simulate the load-settlement behaviour at higher working loads. The group pile analysis results provide a better load-settlement prediction when incorporating an interface zone thickness of pile dimeter from the pile shat using Hardening-Soil model while leaving the remaining soil as Linear-Elastic material.

Japanese Geotechnical Society Special Publication, 2016

In the early stages of design and analysis of structures that are supported by piled foundation, the stiffness of piles is often required to be evaluated. Without going through the complication of pile-soil system, piles can be simulated as springs if the load-settlement behavior of each pile is accurately determined. In this paper, the governing differential equation of pile displacement problem is implicitly solved through a sequence of computation steps. A simple Matlab M-file is built up to perform the computations and present the analysis results. The proposed computation scheme accounts for the nonlinearity of soil mechanical properties and for the non-homogeneity of the soil profile along the pile depth. Consequently, an iterative loop of recalculation and tolerance checking is used and convergence is achieved very rapidly. The procedure is then applied to calculate the pile-settlement behavior of an 1800 mm diameter and about 18m length concrete pile installed in dense to very dense sandy soil. The pile which has a working load of about 6670 kN, is one of the New Hindiya railway bridge piles located in the central part of Iraq. The pile was in situ tested under an axial load of about twice the working load. The results obtained by the proposed computation method compared well (the deviation is less than 10%) with the test results in terms of pile load settlement behavior. This may enhance the reliability of the proposed method.

This study investigates the consolidation settlement of a single pile by combining finite element modelling techniques and field data validation. Using Plaxis 2D and 3D, the study considers a series of static load tests performed over time on a pile driven in Florida and explores the performance of different modelling approaches. The pile is modelled with the soft soil advanced constitutive model, embedded beam row and soil volume. Two different geometry configurations are considered in the models. The average discrepancy between the numerical model values and the field measurement values is determined via the Mean Absolute Error (MAE) and the bias error. It was observed that the embedded beam row feature in the model has given satisfying results. The MAE is equal to 0.93, indicating a low discrepancy between the numerical model values and the reference values. Parametric investigations were conducted to explore soft clay parameters influencing displacement changes. Findings showed that the modified swelling index. 𝜅 * is a critical parameter for the analysis, contributing 56% to the overall variation in the results. Cohesion and pile width also influenced, accounting for 22% and 13%, respectively.

2008

When considering the interaction of two media in contact with highly-distinct deformability characteristics failure is often accompanied by the formation within the more deformable medium of a rather thin zone oriented in the direction of the contact surface. This zone, called the soil-structure interface, or simply interface, experiences intense strain localization and plays the role of a kinematic discontinuity characterized by extremely high strain gradients. Quite a large number of civil engineering structures lie in contact with soils. Such is the case, for example, in soil-retaining walls, soil-anchorage rods, soil-piles or micropiles, or soil-reinforcements (e.g. “terre armee”, nailed soils). Failure in these structures occurs mainly due to progressive shearing and is often observed at the interface, in the softer medium (i.e. the soil mass), where stresses and strains are transmitted. The description of the mechanical behaviour, mainly in terms of mobilized friction between ...

International Journal of GEOMATE, 2018

Skin friction distribution occurs due to a relative movement between pile and adjacent soil. Varied factors affecting this movement get the soil to, occasionally, settle more than that of the pile. In this case, negative skin friction distributes along some part of the pile's shaft. Primary consolidation begins after applying surcharge load on ground surface next to pile's head-where pressure will be carried by the pore water until the entire excess pore pressure dissipates and shear stress is mobilized. This paper presents a finite element parametric study to investigate the effect of viscosity on soil settlements and skin friction distribution along the pile during primary consolidation. Single pile in clay soil is modelled using FORTRAN in conjunction with two different soil constitutive models. On the one hand, numerical modeling has been carried out using the elasto-plastic soil behavior-as defined by Matsui-Abe soil constitutive model. On the other hand, the effect of viscosity has been modeled using the elasto-viscoplastic soil model as defined by Sekiguchi-Ohta model. A parametric study has been conducted in order to compare the results of the above two soil models to clarify the viscous impact. FORTRAN 2-D analytical model has been validated by comparing numerical results with two field tests measurements. Viscosity is clearly effective when a specific value of surcharge load is applied. Structural viscosity has increased the soil settlements compared to the other settlements that occurred by using elasto-plastic soil model-where part of the pile induced by negative skin friction becomes greater.

Géotechnique, 1997

A numerical code for the prediction of the settlement of pile groups and piled rafts is presented. The code is based on the interaction factors method; the non-linearity is simulated as suggested by Caputo and Viggiani, that is, concentrating it at the pile±soil interface. In the linear range, the accuracy is checked against known benchmark solutions. A standard procedure, based on the results of load tests on single piles, is suggested for the evaluation of soil properties and for the implementation of the analysis in real cases. Nineteen well-documented case histories are then analysed, calculating for each of them a linear elastic, an equivalent linear elastic and a non-linear solution. Five out of the 19 cases are illustrated in some detail, to allow a deeper insight into the procedure. In all but one of the analysed cases the predicted values of the average settlement are within AE20% of the observed values. The maximum differential settlement is predicted with slightly lesser accuracy. For foundations characterized by a relatively high safety factor, linear and non-linear analyses are essentially equivalent. Some evidence suggests that the low-strain shear modulus, obtained by in situ shear wave velocity measurements, can be successfully employed in the prediction of the settlement. When the safety factor is low, the consideration of nonlinearity becomes mandatory.

17th Pan-American Conference on Soil Mechanics and Geotechnical Engineering . ISSMGE, 2024

The case of a contiguous piles wall, designed as part of the project to rescue a collapsed diaphragm wall, is presented. The pile wall is built in the soft soils of Mexico City; the rescue process process involved the pile wall, excavation with two levels of struts, berms and slopes. The analysis and design were carried out through numerical modeling, using the finite element method, and includes the effect of soil arching between piles. The advantages and disadvantages of modeling the piles as volume elements or beams are shown. Some aspects observed during construction are highlighted, which demonstrate the correct functioning of the wall. Measurements of displacements on the wall are shown, as well as a comparison with the ones estimated with numerical modeling

Computers and Geotechnics, 2008

A method of settlement analysis for axially loaded piles with rectangular cross section embedded in a multi-layered soil medium is presented. The differential equations governing the displacements of the pile-soil system are obtained using variational principles. Closed-form solutions for pile deflection and axial force along the pile shaft are then produced by using the method of initial parameters. The input parameters needed for the analysis are only the pile geometry and the elastic constants of the soil and pile.

Port-Said Engineering Research Journal

In Egypt, large diameter piles are used in some sites with diameters exceeding 2 m. In some cases, these piles carry foundations of heavy structures and/or large vertical and lateral loads. The analysis and design methodologies of large diameter piles are mainly controlled by the relatively smaller diameter piles, usually ranging between 60 and 120 cm. However, there is a special need for the analysis and design of larger diameter piles (i.e., larger than 120 cm) to assess their actual load carrying capacities. This paper presents numerical modeling of end bearing piles constructed in thick layer of soft to very soft clay underlain by a dense sand layer, typical to large zones in Northern and North Eastern zones in Egypt. The finite element analysis software ADINA (2018) [2] is used to simulate the behavior of the large diameter bored piles. Results showed that increasing the pile diameter cause a corresponding increase in pile capacity. It is also noticed that increasing pile embedded length in the end bearing sand layer has an enormous effect on pile capacity especially for larger diameter piles. .

Acta Geotechnica, 2016

Presented in this paper are results of two centrifuge tests on single piles installed in unimproved and improved soft clay (a total of 14 piles), with the relative pile-soil stiffness values varying nearly two orders of magnitude, and subjected to cyclic lateral loading and seismic loading. This research was motivated by the need for better understanding of lateral load behavior of piles in soft clays that are improved using cement deep soil mixing (CDSM). Cyclic test results showed that improving the ground around a pile foundation using CDSM is an effective way to improve the lateral load behavior of that foundation. Depending on the extent of ground improvement, elastic lateral stiffness and ultimate resistance of a pile foundation in improved soil increased by 2-8 times and 4-5 times, respectively, from those of a pile in the unimproved soil. While maximum bending moments and shear forces within piles in unimproved soil occurred at larger depths, those in improved soil occurred at much shallower depths and within the improved zone. The seismic tests revealed that, in general, ground improvement around a pile is an effective method to reduce accelerations and dynamic lateral displacements during earthquakes, provided that the ground is improved at least to a size of 13D 9 13D 9 9D (length 9 width 9 depth), where D is the outside diameter of the pile, for the pile-soil systems tested in this study. The smallest ground improvement used in these tests (9D 9 9D 9 6D), however, proved ineffective in improving the seismic behavior of the piles. The ground improvement around a pile reduces the fundamental period of the pile-soil system, and therefore, the improved system may produce larger pile top accelerations and/or displacements than the unimproved system depending on the frequency content of the earthquake motion.