Keywords: Fondation ; Mur de soutenement ; Pieux ; Capacite portante ; Ancrage ; Dimensionnement Reference Record created on 2004-09-07, modified on 2016-08-08

Foundation analysis and design

Impact of Variability in Soil Parameter on Culvert Load Rating

Simplified models of railway tracks can provide quick reply to some fundamental issues. However, when nonlinear effects like irreversible ballast deformations are important, a detailed model involving all structural details is preferable. Such a model can be solved by the finite element method, but then it is difficult to choose the correct (i) size of the model, (ii) size of the finite elements and (iii) type of boundary conditions. Techniques based on a moving window method could overcome some of these difficulties. The moving window method is based on the assumption that the load is kept still, while the track model (or a part of it) moves in the direction opposing the originally supposed load movement. This can be accomplished by several techniques, from which the simplest one is to shift the results of the current time step against the load. Nevertheless, in commercial finite element software such an operation is usually protected against inappropriate usage. Alternatively, some results of the current time step can be moved in form of initial conditions for the next time step, but then, if the boundary conditions are violated, the results can start to diverge from the pretended objective. In this contribution two new techniques are proposed. The enhanced moving window method is introduced and implemented in commercial finite element software. In addition, and for handling irreversible nonlinearities, an approach based on time-dependent boundary conditions on the front and rear faces of the moving window is established. The methods proposed have several advantages, some of them are listed as: (i) the model itself can be rather small, but the time dependent results can cover an arbitrarily large model; (ii) quasi- stationary results can be obtained; (iii) in the linear case the effect of a set of loads can be achieved by superposition of previous results; (iv) in the nonlinear case the effect of repeated loads can be accounted for by implementation of the time-dependent boundary conditions. Several one- two- and three-dimensional case studies are analyzed. Influence of various parameters is studied. Accuracy is verified by comparison with analytical solutions or with results of the long simulation on large models. L 2 -norm is used for accuracy evaluation.

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The moving window method and time-dependent boundary conditions: applications to high-speed tracks

This paper presents a description and the results of instrumented macro-scale laboratory indentation testing of Champlain Sea Clay with a stainless steel, flat-tipped, cylindrical indenter. The results of the tests were analyzed using published analytical solutions for the indentation testing of elastic–plastic materials. The relationship between the depth of indentation, h, and the load on the indenter, P, the hardness, the undrained shear strength and the Young’s modulus of the clay were determined from these methods. The undrained shear strength and Young’s modulus were compared to values from conventional geotechnical testing. Indentation testing was simulated numerically using the finite element method. The clay was modelled using the conventional Mohr–Coulomb elastic–plastic model. The distribution of total vertical stress below the indenter from the simulations compared well with an analytical solution based on elastic theory. The simulations using material properties derived from the conventional geotechnical tests (Set 1) and derived from the indentation testing (Set 2) with a Poisson’s ratio of 0.49 (undrained loading) did not produce load-penetration (P–h) curves in good agreement with the curves from indentation testing. However, simulations with the material properties derived from indentation testing and a Poisson’s ratio of 0.2 (drained loading), produced load-penetration curves in good agreement with the indentation testing results.

Foundation analysis and design

Citations

Impact of Variability in Soil Parameter on Culvert Load Rating

The moving window method and time-dependent boundary conditions: applications to high-speed tracks

Indentation of a Sensitive Clay by a Flat-Ended Axisymmetrical Punch

Well-posedness and stability results for a swelling porous-heat system of second sound

Numerical Estimation of Bearing Capacity of Shallow Footings Resting on Layered Sand

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