Mohammad Rezania

A new genetic programming model for predicting settlement of shallow foundations

In this paper, a new genetic programming (GP) approach for predicting settlement of shallow foundations is presented. The GP model is developed and verified using a large database of standard penetration test (SPT) based case histories that involve measured settlements of shallow foundations. The results of the developed GP model are compared with those of a number of commonly used traditional methods and artificial neural network (ANN) based models. It is shown that the GP model is able to learn, with a very high accuracy, the complex relationship between foundation settlement and its contributing factors, and render this knowledge in the form of a function. The attained function can be used to generalize the learning and apply it to predict settlement of foundations for new cases not used in the development of the model. The advantages of the proposed GP model over the conventional and ANN based models are highlighted.

An Evolutionary-Based Data Mining Technique for Assessment of Civil Engineering Systems

Purpose – Analysis of many civil engineering phenomena is a complex problem due to the participation of a large number of factors involved. Traditional methods usually suffer from a lack of physical understanding. Furthermore, the simplifying assumptions that are usually made in the development of the traditional methods may, in some cases, lead to very large errors. The purpose of this paper is to present a new method, based on evolutionary polynomial regression (EPR) for capturing nonlinear interaction between various parameters of civil engineering systems.Design/methodology/approach – EPR is a data‐driven method based on evolutionary computing, aimed to search for polynomial structures representing a system. In this technique, a combination of the genetic algorithm and the least‐squares method is used to find feasible structures and the appropriate constants for those structures.Findings – Capabilities of the EPR methodology are illustrated by application to two complex practical civil engineering pro...

An evolutionary based approach for assessment of earthquake-induced soil liquefaction and lateral displacement

Prediction of liquefaction and the resulting lateral displacement is a complex engineering problem due to heterogeneous nature of soils and participation of a large number of factors involved. In this paper new models are developed, based on evolutionary polynomial regression (EPR), for assessment of liquefaction potential and lateral spreading. The models developed for liquefaction and lateral spreading are compared to those obtained from neural network and linear regression based techniques. It is shown that the developed models are able to learn the complex relationship between either of these problems and their contributing factors in the form of a function with high level of accuracy (mostly in excess of 90%). The results of the EPR model developed for the liquefaction determination are used to find a novel 3-D boundary surface that discriminates between the cases of occurrence and non-occurrence of liquefaction. The developed boundary surface is employed to calculate the factor of safety against liquefaction occurrence.

Intelligent finite element method: An evolutionary approach to constitutive modeling

In this paper, a new approach is presented, for constitutive modeling of materials in finite element analysis, with potential applications in different engineering disciplines. The proposed approach provides a unified framework for modeling of complex materials, using evolutionary polynomial regression-based constitutive model (EPRCM), integrated in finite element analysis. Evolutionary polynomial regression (EPR) is a computing technique that generates a transparent and structured representation of the system being studied. The main advantage of EPRCM over conventional constitutive models is that it provides the optimum structure for the material constitutive model representation, as well as its parameters, directly from raw experimental (or field) data. The proposed algorithm provides a transparent relationship for the constitutive material model that can readily be incorporated in a finite element model (FEM). The incorporation of EPRCM into FEM will be presented and the application of the resulting methodology for material modeling in finite element analysis will be illustrated through two examples.

Comparison of Anisotropic Rate-Dependent Models for Modeling Consolidation of Soft Clays

Two recently proposed anisotropic rate-dependent models are used to simulate the consolidation behaviour of two soft natural clays: Murro clay and Haarajoki clay. The rate-dependent constitutive models include the EVP-SCLAY1 model and the Anisotropic Creep Model (ACM). The two models are identical in the way the initial anisotropy and the evolution of anisotropy are simulated, but differ in the way the rate-effects are taken into consideration. The models are compared first at the element level against laboratory data and then at boundary value level against measured field data from instrumented embankments on Murro and Haarajoki clays. The numerical simulations suggest that at element the EVP-SCLAY1 model is able to give a better representation of the clay response under oedometric loading than ACM, when the input parameters are defined objectively. However, at boundary value level the issue is not as straightforward, and the appropriateness of the constitutive model may depend heavily on the in situ overconsolidation ratio (OCR).

Probabilistic evaluation of seismic liquefaction potential in field conditions: A kinetic energy approach

Purpose – In this paper, the peak kinetic energy density (KED) of soil particles during earthquake excitation is used as an intensity measure for the evaluation of liquefaction potential under field conditions. The paper seeks to discuss this measure.Design/methodology/approach – Using centrifuge tests data, it is shown that seismic pore water pressure buildup is proportional to cumulative KED at a particular soil depth. Linear relationships are found between cumulative kinetic energy and corresponding cumulative strain energy. To consider the effect of soil amplification, several equivalent linear ground response analyses are performed and the results are used to derive an equation for depth reduction factor of peak kinetic energy density. Two separate databases of liquefaction case histories are used in order to validate the proposed model. The performance of the proposed model is compared with a number of commonly used shear stress‐based liquefaction assessment methods. Finally, the logistic regression...

The comparison of modelling inherent and evolving anisotropy on the behaviour of a full-scale embankment

The behaviour of a full-scale embankment constructed on a soft soil deposit has been studied using two different anisotropic elasto-plastic constitutive models, namely S-CLAY1 and Sekiguchi–Ohta (SO) inviscid, in order to investigate the influence of modelling (initial) inherent and evolving anisotropy on boundary value level simulations. The initial inherent anisotropy which is generally modelled by a rotated yield surface can also influence the model prediction capability. A Finnish test embankment known as Murro embankment was chosen for finite-element analysis using the two advanced soil models. The predictions of each model were studied and compared with measured field data. For the purpose of model comparison, the influence of evolution of anisotropy was further investigated by using only the inherent anisotropy feature of S-CLAY1 model, by setting the values of rational hardening parameters to zero. Overall, the S-CLAY1 model predictions are in good agreement with the measured data, which is due to the incorporation of a rotational hardening law (evolution of anisotropy) into the model in addition to the consideration of inherent anisotropy. However, the SO inviscid model predictions are less comparable with the measured data due to the consideration of only the inherent anisotropy into the model. The results clearly demonstrate the importance of including soil’s evolving anisotropy in the analysis and how the inherent anisotropy is modelled (i.e. the shape of yield surface).

An Experimental study of the initial volumetric strain rate effect on the creep behaviour of reconstituted clays

Clayey soils tend to undergo continuous compression with time, even after excess pore pressures have substantially dissipated. The effect of time on deformation and mechanical response of these soft soils has been the subject of numerous studies. Based on these studies, the observed time-dependent behaviour of clays is mainly related to the evolution of soil volume and strength characteristics with time, which are classified as creep and/or relaxation properties of the soil. Apart from many empirical relationships that have been proposed in the literature to capture the rheological behaviour of clays, a number of viscid constitutive relationships have also been developed which have more attractive theoretical attributes. A particular feature of these viscid models is that their creep parameters often have clear physical meaning (e.g. coefficient of secondary compression, Cα). Sometimes with these models, a parameter referred to as initial/reference volumetric strain rate, has also been alluded as a model parameter. However, unlike Cα, the determination of and its variations with stress level is not properly documented in the literature. In an attempt to better understand , this paper presents an experimental investigation of the reference volumetric strain rate in reconstituted clay specimens. A long-term triaxial creep test, at different shear stress levels and different strain rates, was performed on clay specimen whereby the volumetric strain rate was measured. The obtained results indicated the stress-level dependency and non-linear variation of with time.

Transport in Porous Media with Nonlinear Flow Condition

We investigate local aspects and heterogeneities of porous medium morphology and relate them to the relevant mechanisms of momentum transfer. In the inertial flow range, there are very few experimental data that allow to recognize the effects of porous structure on the flow and transport through porous media. An experimental analysis was performed in order to understand above processes at different Reynolds numbers in randomly structured porous media. The objective of the analysis is to explore the effects of porous media particle size on inertial and viscous forces and determine range of the Reynolds numbers in which the inertial flow predominantly contributes in dispersive processes. Transport characteristics of the randomly structured porous media and the influence of inertial force on longitudinal and transverse dispersion coefficients were studied.

Modeling Pile Setup in Natural Clay Deposit Considering Soil Anisotropy, Structure, and Creep Effects: Case Study

AbstractThis paper reports the results of a numerical investigation of the behavior of a natural soft clay deposit under the installation of a case study pile. The case study problem included installation of an instrumented close-ended displacement pile in a soft marine clay deposit, known as Bothkennar clay, in Scotland. The site has been used for a number of years as a geotechnical test bed site, and the clay has been comprehensively characterized with both in situ tests and laboratory experiments. The soft soil behavior, both after pile installation and subsequent consolidation, was reproduced by using an advanced critical-state-based constitutive model that accounts for the anisotropy of soil fabric and destructuration effects during plastic straining. Furthermore, a time-dependent extension of the model was used to study soil creep and the significance of its consideration in the overall pile-installation effects. The simulation results were compared against field measurements; furthermore, for compa...