Papers by Keyword: Geomaterial

Abstract: The composition of the energy in the process of material deformation and failure and the relationship between energy and strength were summarized; the features, essences and main problems of the energy release rate theory, the three-shear energy theory and the net shear strain energy density theory were illustrated. It is pointed out that the roles of distortion strain energy, volumetric strain energy and dissipated energy are not identical, especially distortion strain energy and volumetric strain energy must be separately processed. The three-shear energy theory and the net shear strain energy density theory can properly deal with the problems, and also well reflect the intermediate principal stress effect. The above research results can provide references for further discussions.

Abstract: In designing earth structures, various kinds of complex soils and rocks are constantly encountered. These geomaterials exhibit heterogeneous, nonlinear, and anisotropic behavior. A failure criterion for such complicated materials is proposed. This model is highly comprehensive. It characterizes heterogeneity, nonlinearity, and anisotropy simultaneously in one equation. Many classical failure criteria employed in geomechanics and plasticity are its special cases. The material parameters in the proposed criterion may be determined from tests of unconfined compression, uniaxial tension, biaxial compression, and direct shear. The case study illustrates the potential of the proposed model in engineering application.

Abstract: It is well-known that soils may display strong nonlinear and inelastic characteristics. Furthermore, the viscosity or rheology of soft clays cannot be usually overlooked in the design of major structures founded on soft ground. Especially, rheologic deformation of soils may get considerable under high stress level. In fact, the saturated soft ground usually displays low strength, sensitive thixotropy, and high compressibility. In this paper, the soil deformation on interaction behaviour of piled rafts and soil foundation by using a fully coupled finite-element method of consolidation in which an elasto-viscoplastic model is incorporated. Through numerical computations, it is demonstrated that the coupled creep-consolidation analysis can give a more rational evaluation of overall performance of interaction of piled raft and soils and conventional analyses which overlooks time-dependency of soil deformation may give rise of inaccuracy in engineering evaluation and design of structures.

Abstract: Most soil constitutive models were developed based on the traditional triaxial tests with isotropic assumption, in which the load is applied as the major principal stress direction and the other two principal stresses are symmetric. When such isotropic models are applied to practical analysis, stress induced anisotropy under complex stress state and the middle principal stress effects are often neglected, thus there are many disagreements between the calculated results and the infield testing data. To simulate the practical loading process, true triaxial tests were carried out on geomaterial under three-dimensional stress state. It was found that the stress induced anisotropy effects are remarkable and the middle principal stress effects are obvious because of the initial three-dimensional stress state. Such kind of stress-induced anisotropy could have important impact on the numerical analysis results and should be taken into consideration when developing the constitutive model.

Abstract: The present work focuses on the elaboration of low energy consuming materials and the correlation between their final properties and the fabrication route. For this purpose, geomaterials have been elaborate using a common raw clay material. Also an original route has been developed to elaborate “geomimetic” materials. The raw material consists of lateritic clay, whereas the main reactives are namely: nitric acid, fulvic acid, and calcium hydroxide in an aqueous medium. In both materials, the strengthening process and the final characteristics of the as obtained products have been investigated. Namely: the characteristic compressive strength and the resistance to water seeping and wearing. The geomaterials exhibit a good resistance towards water seeping and wearing, but the products obtained using Portland cement present a greater characteristic compressive strength than with lime. “Geomimetic” materials are also water resistant. In fact, the products elaborated using nitric acid exhibit the best characteristic compressive strength, namely 20 MPa. While with fulvic acid, an environmental friendly organic acid, a characteristic compressive strength of 12 MPa is obtained. Thus the latter appears competitive towards usual stabilized earth and concrete building materials.

Abstract: An explicit dynamic Galerkin meshfree formulation under the updated Lagrangian framework is presented to simulate large deformation damage and failure process in geomaterials. The failure initiation and development are characterized by the pressure sensitive Drucker-Prager plasticity coupled with the isotropic energy-based damage theory. A stabilized conforming nodal integration based on non-local gradient smoothing is employed to improve the computational efficiency and to regularize the material instability arising from strain localization. The capability of the proposed methodology to model the evolution of dynamic failure in geomaterials is demonstrated through a numerical example.