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This paper presents numerical models and mathematical formulations to predict the pullout capacity of anchor plates with different inclination angles embedded in clay. The models were developed based on the failure mechanism deduced from laboratory testing and utilize the Mohr-Coulomb yielding criteria. Expression was given to estimate the maximum pullout resistance of plates with different dimensions and inclination angles embedded in various clayey soils. A comparison between results of finite-element analyses has been performed to find out the effect of different parameters. New two-variable functions have been presented to show the relationship between pullout resistance and embedment ratio with different inclination angles. In addition, an interesting relationship among pullout capacities of anchor plates at different inclination angles was found, and a new concept, ellipse of pullout capacity, has been pronounced. Finally, a new theory has been introduced to predict the pullout capacity of any anchor plates with different inclination angles and various depths, without any computer analysis and just by using the new proposed theory. [ABSTRACT FROM AUTHOR]

This paper presents the results of an analysis of the spatial distribution of the excess pore-water pressure induced by piezocone penetration into overconsolidated clays. From the experimental results obtained for moderately and heavily overconsolidated clays, it was observed that the excess pore-water pressure increases monotonically from the piezocone surface to the outer boundary of the shear zone and then decreases logarithmically, approaching zero at the outer boundary of the plastic zone. It was also found that the size of the shear zone decreases from approximately 2.2 to 1.5 times the cone radius with increasing overconsolidation ratio (OCR), whereas the plastic radius is about 11 times the piezocone radius, regardless of the OCR. The expressions developed in this study based on the modified Cam clay model and the cylindrical cavity expansion theory, which take into consideration the effects of the strain rate and stress anisotropy, provide a good prediction of the initial pore-water pressure at the piezocone location. The method of predicting the spatial distribution of excess pore-water pressure proposed in this study is based on a linearly increasing Δushear in the shear zone and a logarithmically decreasing Δuoct, and was verified by comparing the pore-water pressure measured in overconsolidated specimens in the calibration chamber. [ABSTRACT FROM AUTHOR]

This paper presents the results of 150 finite-element simulations conducted to define the effects of excavation geometry, i.e., length, width, and depth of excavation, wall system stiffness, and factor of safety against basal heave on the three-dimensional ground movements caused by excavation through clays. The results of the analyses are represented by the plane strain ratio (PSR), defined as the maximum movement in the center of an excavation wall computed by three-dimensional analyses normalized by that computed by a plane strain simulation. A simple equation for PSR is presented based on excavation geometry, wall system stiffness, and factor of safety against basal heave. This PSR equation reasonably represents trends in results of the 150 simulations as well as those simulations reported in literature. When the excavated length normalized by the excavated depth of an excavation wall is greater than 6, results of plane strain simulations yield the same displacements in the center of that wall as those computed by a three-dimensional simulation. [ABSTRACT FROM AUTHOR]

Triaxial consolidation undrained shear tests are performed on both undisturbed and remolded Ariake clays to investigate the undrained shear strength behavior. When the applied confining stress is larger than the triaxial consolidation yield stress, the strength envelopes expressed in the plot of undrained shear strength versus confining stress of both the undisturbed and the remolded Ariake clays are straight lines through the origin. The strength envelope of the remolded Ariake clays lies above that of the undisturbed Ariake clays when the applied confining stress is larger than the consolidation yield stress. This difference is caused by the difference in water content between undisturbed and remolded states. When the data obtained from triaxial consolidation undrained shear tests of both the undisturbed and the remolded Ariake clays are plotted in the plot of undrained shear strength versus water content, it is found that the undrained shear strength decreases uniquely with the increase in water content. [ABSTRACT FROM AUTHOR]

This paper presents the findings of a digital image analysis based study of clay fills, compacted with dynamic compaction for a building foundation in northeast Beijing, People’s Republic of China. Three levels of compaction energy were used at three compaction pits, respectively. Ground settlements and soil density increased with the number of dynamic impact blows. Microstructures of dry clay fill samples from the pits were examined with a scanning electronic microscope (SEM). Their microstructural parameters were further measured and analyzed quantitatively using digital image analysis. The clay SEM images are automatically converted into ternary images representing particles, pores, and contact zones for effective and efficient calculation of the clay microstructural parameters. The effect of dynamic compaction on the clay microstructural properties at different blow numbers and compaction energy levels is examined. Analysis revealed that the changes of the soil microstructural properties have a good correlation with the observed ground settlements at the three pits. The ground settlements are due to the size and shape changes and reorientation of the grain particles and pores of the clay fills. [ABSTRACT FROM AUTHOR]

The present contribution reports on a mixed numerical experimental study of the time dependent processes in saturated soils with reference to isotropic consolidation. Owing to its relative simplicity, isotropic consolidation is often viewed as a basic tool for inferring the material parameters of various constitutive models. Within this modeling framework, the paper advocates the use of critical state models for an accurate description of the time dependent deformation of clayey soils. Material models, in which the critical state model applies only to the subcritical region, have been also addressed. Examples include models where the supercritical region is cut off, e.g., by a Mohr–Coulomb surface. Starting with the modified Cam clay model, as a classical representative, the paper revisits a simple isotropic consolidation test. It is suggested that such a conventional laboratory experiment, when combined with a suitable optimization procedure, is sufficient in deriving the desired material parameters, including the initial void ratio, deformation dependent variation of the coefficient of permeability and the preconsolidation pressure representing here an important measure of the structural strength of soils. Several numerical and experimental results are presented to support the theoretical grounds. [ABSTRACT FROM AUTHOR]

The time-dependent behavior of soils has been investigated extensively through one-dimensional and triaxial test conditions. Most of the observations in literature have focused on the determination of the time-dependent behavior of clayey soils, whereas the reported experimental studies of granular materials are few. This paper presents an up-to-date review of the various observed time- and rate-dependent phenomena that are known to exist for both clay and sand. The description is carried out separately for creep, stress relaxation, rate dependency, and structuration in laboratory experiments. All of the above-mentioned phenomena are present in both sand and clay. The time-dependent phenomena are more pronounced in clay than sand. However, sand exhibits relatively large deformations at high confining pressures because of grain crushing. Furthermore, the review revealed an essential characteristic situation for soils. That is whether the time-dependent behavior can be characterized as isotach or nonisotach. It seems that the isotach behavior is adequate for describing the time effects in clays in most situations. But for sand, the isotach description is inadequate. Further, the phenomenon of structuration plays a role in both clay and sand. [ABSTRACT FROM AUTHOR]

Different classes of constitutive models have been developed to capture the time-dependent viscous phenomena (creep, stress relaxation, and rate effects) observed in soils. Models based on empirical, rheological, and general stress-strain-time concepts have been studied. The first part is a review of the empirical relations, which apply only to problems of specific boundary conditions and frequently involve natural time alone. The second part deals with different rheological models used for describing the viscous effects in the field of solid mechanics. The rheological models are typically developed for metals and steel but are, to some extent, used to characterize time effects in geomaterials. The third part is a review of constitutive laws that describe not only viscous effects but also the inviscid (rate-independent) behavior of soils, in principle, under any possible loading condition. Special attention is paid to elastoviscoplastic models that combine inviscid elastic and time-dependent plastic behavior. Various general elastoviscoplastic models can roughly be divided into two categories: Models based on the concept of overstress and models based on nonstationary flow surface theory. Although general in structure, both have shortcomings when used for modeling of soils. [ABSTRACT FROM AUTHOR]