Emilios M. Comodromos

Numerical assessment of axial pile group response based on load test

Abstract Axial pile load tests are considered within the design procedure of most major construction projects that include pile foundations, aiming to determine both the ultimate bearing capacity and the pile stiffness at working load level. Commonly used pile spacings of 3–4 pile diameters between the test pile and the reaction piles cause significant interaction with drastic effect on to the load-settlement relationship. The objective of this paper is to evaluate the influence of this interaction on both bearing capacity and stiffness of single piles and pile groups. For this purpose, a back analysis of a pile load test was initially performed which facilitated the determination of the single pile response and the verification of the soil properties. Subsequently, a numerical analysis was carried out to establish load-displacement relationships for several different layouts of pile groups. Based on these non-linear analyses the effect of the interaction was quantified for both the pile load test and pile group layouts examined.

Effect of Cracking on the Response of Pile Test under Horizontal Loading

Capacity-based design of structures limits the soil-structure interaction mechanism to the determination of the bearing capacity of a pile group. However, in many cases the criterion for the design of piles to resist lateral loads is not the ultimate lateral capacity but the deflection of the piles. Many procedures exist for estimating the response of single piles and pile groups under lateral loading, ranging from application of empirical relationships and simple closed-form solutions to sophisticated nonlinear numerical procedures. With the aim of investigating the effect of cracking, disregarded by most of the above-mentioned methods, a three-dimensional (3D) nonlinear analysis that accounts for cracking is presented. Response prediction correlates well with the experimental data from a full-scale pile load test. Interesting conclusions have also been drawn regarding the discretization of the computational domain and the combination of 3D numerical nonlinear analysis and the structural beam theory.

Numerical Assessment of Subsidence and Adjacent Building Movements Induced by TBM-EPB Tunneling

AbstractA three-dimensional (3D) numerical model simulating a twin tunnel excavated by a tunnel-boring machine (TBM)–earth-pressure balance (EPB) is presented. All relevant components are taken into account, and the influence of the parameters adopted in the TBM-EPB method on the induced ground settlements is investigated. The sensitivity to variations of the face support, the pressure applied to the steering gap slurry, and the tail gap grouting were also evaluated within the framework of parametric analyses. The effects from and on a building located at or beyond the greenfield trough width were also investigated. The greenfield volume loss at the ground surface was found to be 0.85%, increasing to 0.97% at the building foundation level. These values were further increased by 6% at the cross section where the building is located. Furthermore, a full soil-structure interaction using 3D numerical analysis was carried out to evaluate the ability of numerical methods to provide accurate displacement prognos...

Numerical Evaluation of Pile Response Under Combined Lateral and Axial Loading

Piled foundations are frequently subjected to simultaneous axial and lateral loadings. However, the interaction effects of the one loading on the other are, in most cases, disregarded for the sake of simplicity. With the aim of evaluating this effect, a detailed research work on the response of a single pile under simultaneous application of axial and lateral loading was carried out. A qualitative assessment of the effect was initially attempted and the effect was afterwards quantified, based on the results of an intensive three-dimensional parametric numerical analysis. The influence arising from pile head fixity and the second order phenomenon was examined, while the post-peak behaviour was also considered using a strain hardening/softening constitutive law. Interesting conclusions have been drawn, providing a qualitative and quantitative evaluation of the effect on clayey and sandy soils. It was also found that no loading interaction effect is developed, when ultimate limit state is applied for a piled foundation design. On the contrary, when the serviceability limit state is applied and if the pile capacity in both lateral and axial loading is simultaneously reached, a reduction in the pile axial capacity is observed in the case of clayey soils. On the contrary, in the case of sandy soils the action of a lateral load is leading to an increase of pile axial capacity.

Response Prediction for Axially Loaded Fixed Head Pile Groups

The aim of this paper is to evaluate the influence of the interaction between the piles of a group fixed in a pile head on both bearing capacity and stiffness. For this purpose, numerical analyses were carried out to establish the load-displacement relationships for different 3*3 layouts of pile groups. The results are compared with those of the pile test carried out for the purposes of the project and the numerically established load-displacement curve of the single pile. Based on these non-linear analyses, the effect of the interaction was quantified for the pile group layouts examined, and was compared to proposed empirical relationships and reduction factors resulting from linear elastic analyses based on the principle of superposition.