Enhancement of a hypoplastic model for granular soil–structure interface behaviour     

H. Stutz  D. Mašín  F. Wuttke 《Acta Geotechnica》2016,11(6):1249-1261

Modelling of interfaces in geotechnical engineering is an important issue. Interfaces between structural elements (e.g., anchors, piles, tunnel linings) and soils are widely used in geotechnical engineering. The objective of this article is to propose an enhanced hypoplastic interface model that incorporates the in-plane stresses at the interface. To this aim, we develop a general approach to convert the existing hypoplastic model with a predefined limit state surface for sands into an interface model. This is achieved by adopting reduced stress and stretching vectors and redefining tensorial operations which can be used in the existing continuum model with few modifications. The enhanced interface model and the previous model are compared under constant-load, stiffness and volume conditions. The comparison is followed by a verification of two the approaches for modelling the different surface roughness. Subsequently, a validation between available experimental data from the literature versus simulations is presented. The new enhanced model gives improved predictions by the incorporation of in-plane stresses into the model formulation.  相似文献   

Must critical state theory be revisited to include fabric effects?     

Yannis F. Dafalias 《Acta Geotechnica》2016,11(3):479-491

Critical state (CS) is a physically observed state of granular materials at failure, based on which the critical state theory (CST) was founded. CST attempts to describe analytically the material response when CS failure occurs and constitutes the framework within which constitutive modeling techniques have been developed in the last half-century. The conditions of CST defined as necessary and sufficient to characterize CS do not include fabric orientation of material samples. In the present work, this absence of fabric is discussed in light of a newly developed anisotropic critical state theory (ACST) that enhances the classical CST by introducing an additional condition that fabric must satisfy at CS. The use of ACST framework in constitutive modeling is presented in a generic way, usable in conjunction with various constitutive models that comply with CST. Answers to some fundamental questions are attempted or suggested, e.g., as to whether the conditions of classical CST are necessary and sufficient for CS to occur, whether the ACST is simply a convenient supplement to CST or a necessary enhancement, and if the latter is true, the merits and open questions that arise. The presentation focuses on the justification and thoughts behind the proposed specific features of ACST, provides clarifications not made before, while several suggestions and disclaimers are made, and alternate approaches are proposed for further investigations on the subject matter.  相似文献   

Autonomic visiting in digital 3D scenes     

Song Chen  Liang Cheng 《Earth Science Informatics》2016,9(3):383-400

Human-machine interactive visiting and fixed-route visiting are currently the main roaming modes in digital three-dimensional (3D) scenes. However, in general, when a person visits an attraction area, s/he does not follow a fixed path, but instead wander about according to his/her interests. Here, we propose a new roaming mode, called autonomic visiting. That is, in a digital 3D scene, a user selects several interest spots, then a route connecting these spots can be automatically determined and 3D scene can be seen along this route. This study presents a technical approach that enables the realization of autonomic visiting in 3D scenes. Firstly, Delaunay triangular meshes for the terrain in 3D scene are established. Secondly, a plane-growth algorithm and a line-connection algorithm are introduced to automatically mend the broken parts of these triangular meshes. Thirdly, the triangular meshes are then merged and differently weighted according to different layers. Finally, a progress-zone transmission algorithm is presented to optimal the shortest route, which is derived from A-Star (A*) algorithm. Digital 3D campus of Nanjing University, China, is taken as the experimental materials. The experimental results prove the effect of the proposed approach.  相似文献   

Spatial characterization of the seawater upconing process in a coastal Mediterranean aquifer (Plana de Castellón,Spain): evolution and controls     

Olga García-Menéndez  Ignacio Morell  Bruno J. Ballesteros  Arianna Renau-Pruñonosa  Alejandra Renau-Llorens  Mª Vicenta Esteller 《Environmental Earth Sciences》2016,75(9):728

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Temporal and spatial changes in soil micronutrients in managed <Emphasis Type="Italic">Nothofagus pumilio</Emphasis> forest of Tierra del Fuego,Argentina     

Romina Mansilla  Juan Carlos Nóvoa-Muñoz  Xabier Pontevedra-Pombal  Verónica Pancotto  Antía Gómez-Armesto  Julio Escobar  Alicia Moretto 《Environmental Earth Sciences》2016,75(9):738

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An experimental database for the development,calibration and verification of constitutive models for sand with focus to cyclic loading: part I—tests with monotonic loading and stress cycles     

Torsten Wichtmann  Theodoros Triantafyllidis 《Acta Geotechnica》2016,11(4):739-761

For numerical studies of geotechnical structures under earthquake loading, aiming to examine a possible failure due to liquefaction, using a sophisticated constitutive model for the soil is indispensable. Such a model must adequately describe the material response to a cyclic loading under constant volume (undrained) conditions, amongst others the relaxation of effective stress (pore pressure accumulation) or the effective stress loops repeatedly passed through after a sufficiently large number of cycles (cyclic mobility, stress attractors). The soil behaviour under undrained cyclic loading is manifold, depending on the initial conditions (e.g. density, fabric, effective mean pressure, stress ratio) and the load characteristics (e.g. amplitude of the cycles, application of stress or strain cycles). In order to develop, calibrate and verify a constitutive model with focus to undrained cyclic loading, the data from high-quality laboratory tests comprising a variety of initial conditions and load characteristics are necessary. The purpose of these two companion papers was to provide such database collected for a fine sand. The database consists of numerous undrained cyclic triaxial tests with stress or strain cycles applied to samples consolidated isotropically or anisotropically. Monotonic triaxial tests with drained or undrained conditions have also been performed. Furthermore, drained triaxial, oedometric or isotropic compression tests with several un- and reloading cycles are presented. Part I concentrates on the triaxial tests with monotonic loading or stress cycles. All test data presented herein will be available from the homepage of the first author. As an example of the examination of an existing constitutive model, the experimental data are compared to element test simulations using hypoplasticity with intergranular strain.  相似文献   

Shearing characteristics of SCP-inserted clay specimens in triaxial compression test     

Yoon-Sik Choo  Wanjei Cho  Choong-Ki Chung 《Acta Geotechnica》2016,11(1):209-219

Sand compaction piles (SCPs) have been widely applied to the construction on the soft ground for decades, due to not only the acceleration of the consolidation but also the enhancement of strength and stiffness of ground. However, physical behaviors of SCP-improved ground have not been clearly unveiled due to complex response of two distinct materials, compacted sand and soft clay, which are having quite different mechanical characteristics. Therefore, in this study, the mechanical characteristics of SCP composite ground were investigated via triaxial compression tests on SCP-inserted clay specimens. Tests were performed elaborately with four specimens with different replacement ratios. Based on the comparisons of consolidation and shearing behaviors of tested SCP-inserted clay specimens, the SCP effects on the stiffness and strength are also investigated. Even though the SCP-inserted clay specimens show stronger and stiffer behaviors than clay-only specimens, the effects vary on strength, stiffness, and volume change with regard to the applied replacement ratios.  相似文献   

Sand eddies induced by cyclic tilt of a retaining wall     

Chien-Hsun Chen  Dimitrios Kolymbas 《Acta Geotechnica》2016,11(2):269-280

The cyclic tilt of a retaining wall induces a peculiar motion in the backfill (sand), which exhibits closed trajectories (eddies). In this paper, the motion of the backfill has been optically traced and analyzed by means of particle image velocimetry, also known as digital image correlation. The results are of importance for cyclically loaded structures (e.g, piles for off-shore structures) and can also serve to test numerical simulations of large deformation.  相似文献   

Estimation of thermal conductivity of rocks from their mineralogical composition (Asturian Coal Basin,NW Spain) for modelling purposes     

C. Andrés  R. Álvarez  A. Ordóñez 《Environmental Earth Sciences》2016,75(3):266

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Multi-temporal InSAR evidence of ground subsidence induced by groundwater withdrawal: the Montellano aquifer (SW Spain)     

Ana Ruiz-Constán  Antonio M. Ruiz-Armenteros  Francisco Lamas-Fernández  Sergio Martos-Rosillo  J. Manuel Delgado  David P. S. Bekaert  Joaquim João Sousa  Antonio J. Gil  Miguel Caro Cuenca  Ramon F. Hanssen  Jesús Galindo-Zaldívar  Carlos Sanz de Galdeano 《Environmental Earth Sciences》2016,75(3):242

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