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To understand the mesoscopic mechanism of clayey soil in view of macroscopic behavior, it is essential to quantitatively calculate the electric double-layer repulsion between arbitrarily inclined clay particles. However, suitable calculation methods with high efficiency and accuracy are still rare at present in literature. Based on a great number of numerical calculations of the repulsion between two inclined platy clay particles, explicit empirical formulae for estimating electric double-layer repulsion between clay particles are put forward. Comparison between the empirical solutions and corresponding numerical results shows that the proposed formulae have a reasonable accuracy, and application of the presented formula is easy and efficient. Keywords: Clay particles, Electric double-layer repulsion, Numerical analysis, Empirical formula

For one-dimensional soil freezing process, a separate-ice frost heave model is established, and the coupled process of heat transfer, fluid flow and stress development is considered in the model. First, a coupled heat–fluid–stress model describing the growth of a single ice lens is developed by extending the coupled heat–fluid model presented by Zhou and Zhou (Can Geotech J 49(6):686–693, 2012). Second, the mechanism for the formation of a new ice lens in the frozen fringe is studied, and we indicate that if the total vertical disjoining pressure at certain place exceeds the sum of the external pressure and the critical pressure, a new ice lens will emerge. By combining the growth model of a single ice lens and the criterion for the formation of a new ice lens, the separate-ice frost heave model is then established. The difference between the separate-ice model and the rigid-ice model is explained, and the relations for different mathematical models which describe the soil freezing process are also discussed. Numerical analysis of the separate-ice model is conducted using the finite volume method. The freezing tests for Devon silt under no external pressure and Xuzhou silty clay under a constant external pressure are applied to verify the computational results. The consistence between the calculation and the observation validates the separate-ice frost heave model.

The coefficient of earth pressure at rest (K0) for normally consolidated clays increases nonlinearly with increasing consolidation pressure toward a steady value under high pressure rather ...

Consolidated-isotropically undrained triaxial compression (CIUC) tests were performed on the reconstituted deep clay from a mine in East China. It was consolidated to maximum stresses in the range of 0.3–2.6 MPa. The test results show that the stress-strain-strength properties of the clay during undrained shear are significantly stress-dependent. In particular, in the case of high consolidation pressure, the post-peak drop in strength on stress-strain curves and shear plane in soil specimens are more evident, the peak stress ratio and the axial strain at which this ratio was reached are smaller, and the relationship between pore pressure and axial strain is also significantly different from that for the case of low consolidation pressure. The environmental scanning electron microscope observations and micro analysis lead to an understanding of the physical mechanisms underlying the above stress-dependent mechanical behavior. In addition, the CIUC behaviors of the studied clay are discussed in the context of critical state soil mechanics.

In order to investigate the mechanism underlying the reported nonlinear at-rest coefficient of earth pressure,K0of clays at high pressure, a particle-scale model which can be used to calculate vertical and horizontal repulsion between clay particles has been proposed. This model has two initial states which represent the clays at low pressure and high pressure, and the particles in this model can undergo rotation and vertical translation. The computation shows that the majority of particles in a clay sample at high pressure state would experience rotation during one-dimensional compression. In addition, rotation of particles which tends to form a parallel structure causes an increase of the horizontal interparticle force, while vertical translation leads to a decrease in it. Finally, the link between interparticle force, microstructure, and macroscopicK0is analyzed and it can be used to interpret well the nonlinear changes inK0with both vertical consolidation stress and height-diameter ratio.

This For mastering the effect of particle size to strength and deformation characteristics of sand under high pressure, DRS-1 high pressure direct shear test system is used in shear test for 3 groups of sand under pressure of 12 to 15 MPa. Through analysis of the test results, it is obtained that standard sand under high pressure shows strain hardening and volume contraction characteristics. The relationship curves of stress-strain and volume contraction-shear strain appear as hyperbola, they can be simulated by Duncan-Chang hyperbolic model. Sand with small particle size has better group, greater density and higher strength, but the shear contraction is not obvious. Sand with poor group has particle crushing under high pressure, which makes the soil particles rearrange and then the average porosity decreases at the same time large pores disappear, so finally it shows a more significant shear contraction characteristic.

Analysis of the expansion of cylindrical and spherical cavities in soil and rock provides a versatile and accurate geomechanics approach for study of important problems in geotechnical engineering. As the method getting more important, the analysis of non-circular shape cavity is becoming significance. The paper has investigated the cavity wall shape varying characteristic and elasto-plastic distribution of stress of elliptic shape cavity under internal uniform pressure during the expansion period through ABAQUS FEM numerical. It pointed that the elliptic cavity wall will tend to circle shape as the internal uniform pressure increasing. It also gain that the elasto-plastic distribution around the elliptic cavity is bigger than spherical cavity’s and smaller than spherical cavity’s when material and pressure are same . The stress characters and the cavity wall transfiguration result is useful for estimate non-circular shape cavity expansion.

At-rest earth pressure codfficient,K0,is very important in geotechnical engineering design and finite element analysis. At present, it’s treated as a constant usually for given soil in FEM analysis. However recent test results indicate that K0of both clay and sand varies with pressure increasing nonlinearly. It’s shown that Duncan-Chang model, a kind of hypoelastic model widely used, can reproduce K0varying with pressure. The calculating procedure of K0derived from Duncan-Chang’s E-B model is proposed, and then influence of model parameters on calculated K0is explored. Studies show that cohesionless soil’s calculated K0decreases with pressure increasing, while cohesive soil’s calculated K0increases with pressure increasing. Three of the seven model parameters, m, Kband Rf, have a positive correlation with calculated K0, and there is a negative correlation between the residual parameters and calculated K0.The influence of seven model parameters on the calculated K0decreases gradually in the following order: m ,n, Rf, φ, c, K, Kb.

In this paper, experimental research on the response of frost heave in intermittent freezing mode characterized by different frequencies and amplitudes was carried out in opening system, temperature distribution, temperature gradient and evolution of frost heave in the soil samples made up of Tibetan silty clay were acquired and analyzed. Based on frost heave model of coupled heat and moisture, compiled program to simulate the temperature distribution and evolution of frost heave in soil samples in opening system, the simulated results agreed well with the experimental values and showed that the continuous-intermittent freezing mode was effective for restraining the magnitude of frost heave, and the various responses of frost heave in frozen soils were caused by different intermittent freezing modes characterized by frequencies and amplitudes.

Efficient calculation of the electrostatic interactions including repulsive force between charged molecules in a biomolecule system or charged particles in a colloidal system is necessary for the molecular scale or particle scale mechanical analyses of these systems. The electrostatic repulsive force depends on the mid-plane potential between two charged particles. Previous analytical solutions of the mid-plane potential, including those based on simplified assumptions and modern mathematic methods, are reviewed. It is shown that none of these solutions applies to wide ranges of inter-particle distance from 0 to 10 and surface potential from 1 to 10. Three previous analytical solutions are chosen to develop a semi-analytical solution which is proven to have more extensive applications. Furthermore, an empirical closed-form expression of mid-plane potential is proposed based on plenty of numerical solutions. This empirical solution has extensive applications, as well as high computational efficiency.