A weak form quadrature element formulation for consolidation analysis of non-homogeneous saturated soil is established based on Biot’s theory. Numerical examples are given, and the results are ...compared with the analytical solutions available or those from the commercial finite element software ABAQUS, demonstrating accuracy and rapid convergence of quadrature element solutions. The disparity between various treatments of non-homogenous soil is discussed, and the effectiveness and advantages of the quadrature element formulation in consolidation analysis of non-homogeneous soil are demonstrated.
The response of rectangular rigid footings resting on an elastic soil of shear modulus decreasing monotonically with depth is studied. Such profiles are typically encountered after ground ...improvement. The propagation characteristics of SV/P surface waves are investigated, showing the appearance of cut-off frequencies above which surface waves do not exist. The semi-analytical method of the subdivision of the footing/soil contact area is then used for solving the boundary value problem, whereby the influence functions for the sub-regions are determined by integration of the corresponding surface-to-surface Green׳s functions. Impedance functions are presented over a wide range of frequencies for typical values of the non-homogeneity parameters, the Poisson׳s ratio and the foundation geometry. The salient features that are associated with the non-homogeneity and the appearance of cut-off frequencies are elucidated.
•Frequency-domain analysis of a half-space with shear modulus decreasing with depth.•Appearance of cut-off frequencies for the propagation of SV/P surface waves is shown.•Cut-off frequencies depend on the Poisson׳s ratio and modulus depth-profile.•Impedances for footings are evaluated both for absence/presence of surface waves.•Main feature is the increase in damping in the low to medium frequency range.
The purpose of this study is to analyze the behavior of the structural foundation of transmission line towers as a grounding system. Using the Segmentation-Integration method implementation available ...in industry-standard software, a typical tower structure is analyzed under different scenarios, with a compreheensive assessment of current distributions, GPR, touch and step voltages for different values of concrete electrical resistivity, considering a non-homogeneous soil. The results show that in soils with two layers, if the resistivity of the top layer is lower than of the bottom layer, then the tower foundation grounding performance may become impaired, depending on the characteristics and humidity state of the concrete. However, the association of counterpoise conductors with the foundation shows satisfactory results. If the top soil layer has a higher resistivity than the bottom layer, the foundation itself may be sufficient to ensure effective grounding dispersion.
By means of a semi-analytical FE approach an embedded circular footing under monotonic horizontal and moment loading is studied. In a non-homogeneous soil whose shear modulus is characterized by a ...power law variation with depth, horizontal, rocking and coupled modes of displacement, expressed in terms of influence factors are thoroughly examined. The exponent α that controls the shape of the stiffness variation with depth is termed shear modulus factor. Surface influence coefficients are considered for the situations where the interface between the soil and the footing is either perfectly rough or perfectly smooth. First, results of semi-analytical FE analysis in the case of rough footing are established and compared with those of another numerical method. Results of comparison show good agreement. Then, for different values of α the surface influence coefficients are presented for an embedded footing in perfect smooth contact with soil. The metacentre is referred to as the depth at which there is no coupling between the sliding and the rocking modes of footing deformations. Expressions for location and horizontal influence coefficient corresponding to this particular depth are developed and their variations with α examined. The paper finishes by showing the effect of interface conditions on the soil normal stresses developed beneath the embedded circular footing for the case of loading applied at the footing top.
An efficient computer-based method for evaluation of an optimal two-layer soil model from Wenner four probe test data is presented. The method is based on recently developed finite expressions for ...computation of potential in two-layer soil. The coefficients of the formulae have been readjusted to suit the present application. A computer program SPEF (Soil Parameters Estimation using Finite Expressions) based on the proposed method is described. The accuracy and efficiency of the method are established by determining two-layer soil models for several sets of apparent resistivity data. SPEF is shown to be much more efficient and convenient than programs based on infinite series expressions.< >
Many international standards highlight the relevance of studying the compatibility of forces and displacements between the structure and the foundation that supports it. In the case of pile ...foundations, some authors use continuum models that rigorously reproduce the interaction of the pile with the surrounding soil. However, their high computational cost justifies the use of simplified methodologies that allow obtaining sufficiently accurate results in significantly less time. This work presents a surrogate model based on Artificial Neural Networks (ANNs) trained from a synthetic dataset generated by a continuum numerical model. A good regression capacity is observed by the proposed model, also requiring very short evaluation times. Two use examples are presented to illustrate the smooth behaviour of the ANNs model and its ability to determine the critical pile length. This surrogate model allows introducing soil–structure interaction in problems with large volume of evaluations in a feasible way without significantly compromising the confidence of the results.
•An ANN-based model can reproduce the pile stiffness in a non-homogeneous soil.•The proposed model agrees with analytical expressions present in the literature.•Active length of the pile is adequately reproduced by the surrogate model.
This study investigated the effect of reducing seepage under a hydraulic structure. This article aims to find positional equations for the control devices that reduce the seepage under the hydraulic ...structure. Using lengths and angles of sheet-piles under the hydraulic structure where the sheet-pile was placed up- and downstream, respectively, upon the hydraulic structure with anisotropy soil hypothetically affects both uplift pressure and seepage values. The experiments were conducted in two cases: in the first case, a couple of sheet-piles were oriented to the upstream passage; while in the second case, they were oriented to the downstream. Then, the second case was compared with three sheet-piles placed upstream, downstream, and intermediate to the passage. For each experiment (at the hydraulic toe position), the major affecting parameters such as the uplift pressure, gradient exit, and outlet flow rate were found. A correlation equation to correlate the exit gradient and discharge parameters was developed.
A lightning strike is considered one of the most risky natural phenomena that can lead to human harmful and the surrounding soil layers. To tackle this issue, this article investigates the influence ...of direct lightning characteristics in terms of human body safety. Specifically, such investigation is carried out on the effect of resistivities of two-layer soils on human safety when lightning stroke hits the towers of the high voltage transmission lines (HVTLs). The merit of the proposed study is that the soil ionization phenomenon is taken into consideration. Further, the study focuses on the current passing through the human heart, when step and touch (contact) voltages are generated by grounding potential rise, caused by direct lightning strikes transmission tower and the produced potential rise that a person could be exposed. Also, studying the effects of peak current and time of lightning strokes are investigated. Additionally, the paper presents the effect of different reflection factors on human safety. For validation purposes, the ATP program is used in the simulation of the grounding system as well as the human body model. Numerous simulations were accomplished in order to examine the behavior of the current passing through with the human heart. Based on the simulation results, it was concluded that the soil characteristics have superior influences on the contact and step potentials and, accordingly, the survival threshold.
