Numerical Methods In Geotechnical Engineering Research Articles

FEM Simulations of Granular Matter Behaviour Under Triaxial Tests

This article presents the results of a numerical simulation carried out from a series of standard triaxial tests conducted on limestone sand from a quarry situated in Algiers (center of Algeria). The main objective of the investigation is to obtain from a numerical analysis a simple soil model to represent the behaviour of the studied material. The 2D Plaxis program is used in this study with the introduction of a model based on the work of Brinkgreve et al. (in: Benz T, Nordal S (eds) Numerical methods in geotechnical engineering, CRC Press, Boca Raton, 2010). Corrections were made to the formulas used, which are based on the relative density, in order to improve the quality of the results in terms of soil behaviour, mechanical strength and deformation. The comparison of the experimental and numerical results for the Mohr–Coulomb model gives a considerable appreciation on the deformation and resistance. However, it fails to represent properly the stress–strain curve. The use of Duncan and Chang model (Hardening Soil Model-HSM) leads to an underestimation of the resistance characteristics (values of the friction angles) with an overall error of 7.98%. Our work consists of the application of two corrections to the HSM model. The first correction is based on the work of Brinkgreve et al. (2010), which focused on the common parameters between the HSM and the HSSM. An overestimation of the deformations was observed with an overall error of 155.96%. The second step consists of canceling the correction of the elastic modules ( $$E_{50}^{ref}$$ , $$E_{oed}^{ref}$$ ) which reduces the error to 1.53%.

A New Contact Formulation for Large Frictional Sliding and Its Implement in the Explicit Numerical Manifold Method

Modelling discontinuous systems involving large frictional sliding is one of the key requirements for numerical methods in geotechnical engineering. The contact algorithms for most numerical methods in geotechnical engineering is based on the judgement of contact types and the satisfaction of contact conditions by the open–close iteration, in which penalty springs between contacting bodies are added or removed repeatedly. However, the simulations involving large frictional sliding contact are not always convergent, particularly in the cases that contain a large number of contacts. To avoid the judgement of contact types and the open–close iteration, a new contact algorithm, in which the contact force is calculated directly based on the overlapped area of bodies in contact and the contact states, is proposed and implemented in the explicit numerical manifold method (NMM). Stemming from the discretization of Kuhn–Tucker conditions for contact, the equations for calculating contact force are derived and the contributions of contact force to the global iteration equation of explicit NMM are obtained. The new contact algorithm can also be implemented in other numerical methods (FEM, DEM, DDA, etc.) as well. Finally, five numerical examples are investigated to verify the proposed method and illustrate its capability.

Fatores de redução para fluência em geocomposto drenante

A construção civil, muitas vezes considerada atrasada tecnologicamente quando comparada a outros setores, tem buscado incorporar novas tecnologias às suas atividades tradicionais. Na engenharia geotécnica, pode-se destacar o uso crescente dos materiais geossintéticos como evidência. O uso de geocompostos drenantes com a finalidade de captação e condução da água presente no solo tem se tornado cada vez mais frequente. Conhecer e compreender o comportamento deste tipo de material pode representar um dimensionamento mais preciso e, consequentemente, uma maior segurança na aplicação e redução de custos para implementação deste tipo de solução. O estudo busca medir o desempenho de um geocomposto drenante a partir de resultados de ensaios de laboratório para obtenção das características mecânicas, hidráulicas e de durabilidade do geossintético. Com os parâmetros obtidos foi feita uma correlação entre os ensaios de compressão, transmissividade e fluência. Deste modo foi possível fazer a previsão da redução na capacidade de vazão do material em longo prazo, estabelecendo fatores de redução quanto à fluência, específicos para este tipo de material. Baseando-se nos resultados obtidos, o material mostrou um desempenho considerado bastante satisfatório.

Calibration of an advanced material model for a shotcrete lining

Proper choice of a constitutive model is an essential part of any successful application of numerical methods in geotechnical engineering. In most cases, attention is paid to the soil constitutive model. For structural elements, such as tunnel linings, retaining structures etc. elastic constitutive models are often used. These material models however do not involve many aspects of a real structural behavior such as limited tensile and compressive strength, strain softening and time dependent behavior during service life of a construction. In the proposed paper, an application of the novel constitutive model for shotcrete (Schädlich, Schweiger, 2014) is presented. The paper is focused at the process of determination of input parameters values of this model based on performed laboratory test. Section of the primary collector network in Brno was chosen for the purpose of obtaining shotcrete lining samples.

Numerical simulation of evapotranspiration using a root water uptake model

Abstract The abstraction of ground water by vegetation and its influence on the behaviour of geotechnical structures such as pavements, foundations and slopes has been researched for many years. In recent years, the use of numerical methods in geotechnical engineering has rapidly increased. A major challenge for numerical modelers involves the specification of the surface flow boundary condition to model root water uptake by vegetation. The abstraction of ground water by roots is a complex process which involves the interaction of the atmosphere, vegetation and the ground. Accurate prediction of the pore water pressure changes induced by vegetation requires the development of algorithms which can mimic the process of transpiration by vegetation in the continuity equation of fluid flow. This paper presents a root water uptake model which has been coded into a finite element program that can perform coupled (mechanical and fluid flow behaviour) analyses. The input data includes rainfall, potential evapotranspiration and maximum root depth. The key features of the model are discussed first, followed by a presentation of results from a series of parametric studies.

Modélisation hiérarchisée du comportement des sols

ABSTRACT In this paper, a tool for better controlling the use of constitutive models in numerical methods in geotechnical engineering is proposed. For this purpose a constitutive model based on CJS model is developed. This model is hierarchically composed of several levels of constitutive modelling, respectively from a simple level to a more complex level. The transition from one level to another is easy in operating only over some constants of the model. The strategy of identification and physical meanings for all of the constants are clearly defined. In order to validate the different levels of the model, the results of homogeneous drained and undrained tests, in the same way as boundary problems concerning pressuremeter and tunnel are presented and discussed.

Interview with ITA President Z. Eisenstein

Dr. Zdenek (Dan) Eisenstein has been involved in tunnelling for nearly thirty years. He received his undergraduate and doctoral degrees in civil engineering and geo-technical engineering, respectively, from Czech Technical University, Prague. Since 1969, he has been a professor of civil engineering at the University of Alberta in Edmonton, Canada. His research has been oriented toward design and analysis of undeground structures; deep excavations; soil structure interaction problems; and application of numerical methods in geotechnical engineering. He has develop graduate and professional courses in solid mechanics, foundation engineering, tunnelling, light rail transit, and numerical modelling. Prof. Eisenstein has served as a consultant on several hundred projects throughout the world involving dams, foundations, deep excavations, and tunnels. For the Channel Tunnel project, he was engaged to evaluate the compatibility of the tunnel systems with the ground. A member of the Canadian Geotechnical Society and the advisory board of the International Journal for Numerical Methods in Geomechanics, Prof. Eisenstein served as Editor of Canadian Tunnelling from 1985 to 1989. He has lectured extensively on a wide range of topics related to tunnelling, and has published more than 100 papers in journals and conference proceedings. Prof. Eisenstein has served on the Executive Council of the International Tunnelling Association since 1987; he was elected ITA First Vice-President in 1989 and President in 1991. Midway through his presidency, Prof. Eisenstein talked with Tunnelling and Underground Space Technology about the ITA's accomplishments over the past year-and-a half, and his goals for the remainder of his term of office.

Numerical methods in geotechnical engineering. Edited by C. S. Desai and J. T. Christian. McGraw‐Hill Book Company, 1977. No. of Pages: 783.

Numerical methods in geotechnical engineering. Edited by C. S. Desai and J. T. Christian. McGraw‐Hill Book Company, 1977. No. of Pages: 783.

Numerical methods in geotechnical engineering : Desai, C S; Christian, J T (editors) New York: McGraw-Hill, 1977, 783P

Numerical methods in geotechnical engineering : Desai, C S; Christian, J T (editors) New York: McGraw-Hill, 1977, 783P