Consolidation of partially saturated ground improved by impervious column inclusion:Governing equations and semi-analytical solutions

This study focuses on the consolidation behavior and mathematical interpretation of partially-saturated ground improved by impervious column inclusion.The constitutive relations for soil skeleton,pore air and pore water for partially saturated soils are proposed in the context of partially-saturated ground improved by impervious column inclusion.Settlement equation and dissipation equations of excess pore air/water pressures for a partially saturated improved ground are then derived.The semi-analytical solutions for ground settlement and pore pressure dissipation are then obtained through the Laplace transform and validated by the existing solutions for two special cases in the literature and the numerical results obtained from the finite difference method.A series of parametric studies is finally conducted to investigate the influence of some key factors on consolidation of partially saturated ground improved by impervious column inclusion.Based on the parametric study,it can be found that a higher value of the area replacement ratio or modulus of the pile results in a longer dissipation time of excess pore air pressure(PAP),a shorter dissipation time of excess pore water pressure(PWP),and a lower normalized settlement.

Pellet mixtures in isolation barriers

Granular mixtures made of high-density pellets of bentonite are being evaluated as an alternative buffer material for waste isolation. Ease of handling is an often-mentioned advantage. The paper describes the experimental program performed to characterize the hydro-mechanical （HM） behaviour of compacted pellet mixtures. Grain size distribution was adjusted to a maximum pellet size compatible with the specimen＇s dimensions. Dry densities of statically compacted specimens varied in most of the cases in the range from 1.3 to 1.5 Mg/m^3. Pellets had a very high dry density, close to 2 Mg/m^3. The outstanding characteristic of these mixtures is their discontinuous porosity. Pore sizes of the compacted pellets varied around 10 nm. However, the inter-pellet size of the pores was four to five orders of magnitude higher. This double porosity and the highly expansive nature of the pellets controlled all the hydraulic and mechanical properties of the mixture. Performed tests include infiltration tests using different water injection rates and mechanisms of water transfer （in liquid and vapour phases）, suction-controlled oedometer tests and swelling pressure tests. The interpretation of some performed tests required back analysis procedures using a hydro-mechanical （HM） computer code. Material response was studied within the framework of the elastoplastic constitutive model proposed by Alonso et al. （1990） （Barcelona basic model, BBM）. Parameters for the model were identified and also a set of hydraulic laws are necessary to perform coupled HM analysis. A large scale in-situ test （the ＂EB＂ test in Mont Terri, Switzerland） was described and analyzed. Rock barrier parameters were adjusted on the basis of available tests. The test excavation, barrier emplacement and forced hydration were simulated by means of the CODEBRIGHT program. The comparison between measurements and computed results include data on relative humidity in the rock and the buffer, swelling pressures and displacements.

THE AXISYMMETRIC MIXED BOUNDARY-VALUE PROBLEM OF THE VERTICAL VIBRATION OF A RIGID FOUNDATIONON SATURATED LAYERED SOIL SUBGRADE

Based on the theory of elastic wave propagation in saturated soil subgrade established by the author of this paper, the axisymmetric vertical vibration of a rigid circular foundation resting on partially saturated soil subgrade which is composed of a dry elastic layer and it saturated substratum is studied. The analysis relied on the use of integral transform techniques and a pair of dual integral equations governing the vertical vibration of the rigid foundation is listed under the consideration of mixed boundary-value condition. The results tire reduced to the case for saturated half-space. The set of dual integral equations are reduced to a Fredholm integral equation of the second kind and solved by numerical procedures, Numerical examples are given at the end of the paper and plots of the dynamic compliance coefficient C-b versus the dimensionless frequency a(0) are presented.

Effect of various physical properties on the reflection coefficients of inhomogeneous waves at the stress-free surface of partially saturated soils induced by obliquely incident fast P-wave

Ghasemzadeh and Abounouri[1]developed a mathematical model of partially saturated soils that is solved using the potential method,which decomposes elastodynamics equations into two standard wave equations,a scalar wave equation for scalar potential and a vector wave equation for vector potential.In such a medium,four waves exist three longitudinal and one shear.Each fluid phase tortuous path is taken into account in this model.The inertial coupling between solid and fluid particles is consid-ered.Furthermore,both open-pore and sealed-pore boundaries are explored to investigate the reflection phenomenon at the surface of partially saturated soils.For both boundaries,the reflection coefficients of inhomogeneous waves at a partially saturated soil surface are found as a non-singular set of linear equations.All waves(both reflected and incident)in partially saturated soils are pronounced as inhomogeneous due to viscosity in pore fluids(i.e.,distinct directions of attenuation and propagation).The energy shares of reflected waves are determined using an energy matrix.A numerical example is used to determine the reflection coefficients and the distribution of incident energy among the various reflected waves.The effect of different physical features on reflection coefficients and incident energy partitioning is illustrated graphically.The conservation of incident energy at the surface of partially saturated soils is mathematically confirmed at all angles of incidence.

A discrete contact model for complex arbitrary-shaped convex geometries

The shape of particles has a significant influence on the behavior of suspensions,as the particle-fluid,particle-particle,and particle-wall interactions depend on it.However,the simultaneous consideration of complex particle shapes and four-way coupling remains a major challenge.This is mainly due to a lack of suitable contact models.Contact models for complex shapes have been proposed in literature,and most limit the accuracy of the particle-fluid interaction.For this reason,this paper presents a novel contact model for complex convex particle shapes for use with partially saturated methods,in which we propose to obtain necessary contact properties,such as the indentation depth,by a discretization of the contact area.The goal of the proposed model is to enable comprehensive and accurate studies of particulate flows,especially with high volume fractions,that lead to new insights and contribute to the improvement of existing industrial processes.To ensure correctness and sustainability,we validate the model extensively by studying cases with and without fluid.In the latter case,we use the homogenized lattice Boltzmann method.The provided investigations show a great agreement of the proposed discrete contact model with analytical solutions and the literature.