Three simplified models for the analytic determination of the dynamic response of a crossanisotropic poroelastic half-plane to a load moving with constant speed on its surface are presented and compared against the corresponding exact model. The method of analysis of the exact and approximate models uses complex Fourier series to expand the load and the displacement responses along the horizontal direction of the steady-state motion and thus reduces the partial differential equations of the problem to ordinary ones, which are easily solved. The three simplified models are characterized by reasonable simplifying assumptions, which reduce the complexity of the exact model and facilitate the solution. In the first simplified model all the terms of the equations of motion associated with fluid acceleration are neglected. In the second simplified model, solid displacements are assumed to be equal to the corresponding fluid ones, while the third simplified model is the second one corrected with respect to the fluid pressure at the free boundary (top) layer. All three simplified models are compared with respect to their accuracy against the exact model and the appropriate range of values of the various significant parameters of the problem, like porosity, permeability, anisotropy indices, or load speed, for obtaining approximate solutions as close to the exact solution as possible is thoroughly discussed.

A large diameter triaxial specimen of 61.9 mm was made by mixing coconut shell fibers with red clay soil. The shear strength of coconut shell fiber-reinforced soil was investigated using a dynamic triaxial shear test with confining pressure in a range of 50-250 kPa, a fiber content of 0.1%-0.5%, and a loading frequency of 0.5-2.5 Hz. The Hardin-Drnevich model based on the coconut shell fiber-reinforced soil was developed by analyzing and processing the experimental data using a linear fitting method, determining the model parameters a and b, and combining the influencing factors of the coconut shell fiber-reinforced soil to improve the Hardin-Drnevich model. The results show a clear distinction between the effects of loading frequency and fiber content on the strength of the specimens, which are around 1 Hz and 0.3%, respectively. Hardin-Drnevich model based on coconut shell fiber-reinforced soil can better predict the dynamic stress-strain relationship of coconut shell fiber-reinforced soil and reflect the dynamic stress-strain curve characteristics of the dynamic stress-strain curve coconut shell fiber-reinforced soil.

Due to its particulate nature, the mechanical properties of bulk clay are determined by interparticle forces and fabrics of particle assemblies. A thorough study of the connection between properties across length scales is crucial to a fundamental understanding of the mechanisms behind the complex mechanical behavior of clays and clayey soils. This paper demonstrates the development of a multiscale constitutive model for describing the small-strain elastic properties of illite, based on the results of coarse-grained mesoscale molecular dynamic simulations for monodisperse assemblies of illite primary particles. The formulation consists of a homogenization scheme linking the potential energy of the system with an optimal parameter set describing the mesoscale fabric of the particles, and a perturbation scheme describing the change of the parameters in response to infinitesimal strains applied to the systems. The small strain elastic stiffness tensors are calculated as the second-order derivative of the potential energy with respect to the infinitesimal strain. The results from model prediction are validated against the stiffness properties interpreted from numerical simulations as well as experimental findings from prior research studies. The multiscale constitutive model is able to effectively capture the elastic properties of illite in terms of magnitude and material symmetry purely based on the information of interparticle forces and fabrics.

Meteorites provide access to information on the formation and evolution of planetary bodies which is otherwise difficult to study. The unique nature of these samples and their relative scarcity means that non-destructive analysis techniques are needed to study their properties. This paper uses the laser ultrasound technique spatially resolved acoustic spectroscopy to non-destructively determine both the crystal orientation and the single crystal elastic constants (Cif) of a sample of the Gibeon meteorite. There are no published values to directly compare the results of this study, as non-destructive measurements of the single crystal elasticity on granular material have not been possible. Therefore, comparisons with theoretical values for man-made iron-nickel alloys are given showing the Cif values are in the expected range. There are studies providing bulk elastic properties of meteorites, and so calculated bulk properties derived from the single crystal elasticity measurements are compared and also agree well.

In aggressive environments, including acidic environments, low and high-plasticity clays play an important role in transmitting and spreading dangerous pollution. Stabilisation of these types of soils can improve their characteristics. In this research, different ratios of two precursors with a low calcium percentage, for example, waste statiti-ceramic sphere powder (WS-CSP) and a high calcium percentage (e.g. ground granulated blast furnace slag [GGBFS], were employed to investigate the properties of soils with different plasticity indices [PIs]). Low and high-plasticity-stabilised and stabilised with 5 wt% Portland cement specimens were prepared and exposed to an acidic solution with a pH of 2.5 in intervals of 1, 3, 6 and 9 months. The long-term durability of specimens was evaluated using the uniaxial compressive strength test (UCS) and bending strength test (BS). Additionally, the microstructures of these specimens under various time intervals were analyzed using scanning electron microscopy and Fourier-transform infrared. According to the results, in an acidic environment, the reduction in UCS, BS, toughness and secant modulus of elasticity (E50) for low-plasticity-stabilised specimens and containing 100% WS-CSP was lower than that of other specimens. The Taguchi method and ANOVA were used to investigate the effect of each control factor on the UCS and BS.

Wave propagation in an ocean site is an essential research topic in various scientific fields, such as offshore geotechnical engineering, ocean seismology, and underwater acoustics. Previous studies have considered the seabed soil as elastic or poroelastic, ignoring the viscoelastic characteristics of its solid skeleton. Based on the fractional-derivative viscoelastic theory and the modified Biot theory, considering the flow-independent viscosity related to solid skeleton, this paper proposes a generalized viscoelastic wave equation for a fluid-saturated porous medium. The equation has a flexible mathematical form to describe soil rheological properties more accurately through fractional order. On this basis, the total wave field equation of an ocean site, modeled as the fluid-poroviscoelastic-solid media, is established. Then an analytical solution for wave propagation in an ocean site subjected to obliquely incident P and SV waves is obtained, and its degeneration and extension are studied. The proposed method is comprehensively validated through experiment, analytical, and numerical methods. Finally, a parameter analysis is performed to investigate the effects of water depth, seabed properties (including viscoelastic parameters, fractional order and permeability), and incident angle on the seismic response of a poroviscoelastic seabed.

A novel theoretical model is proposed to investigate the torsional response of a pile in fractional-order viscoelastic unsaturated transversely isotropic soil with imperfect contact. This model employs Biot's framework for three-phase porous media along with the theory of fractional derivatives. Unlike previous models that assume continuous displacement at the pile-soil interface, this study uses the Kelvin model to simulate relative slippage between pile-soil contact surfaces (imperfect contact). Incorporating fractional-order viscoelastic and transversely isotropic models to describe the stress-strain relationship, comprehensive dynamic governing equations are derived. Using the separation of variables method, inverse Fourier transform, and convolution theory, analytical solutions for the frequency domain response and semi-analytical solutions for the time domain response of the pile head under semi-sine pulse excitation are obtained. Using numerical examples, the effects of model parameters in the fractional-order viscoelastic constitutive model, pile-soil relative slip and continuity model, and soil anisotropy on the torsional complex impedance, twist angle, and torque are presented.

In contrast to homogeneous soil deposits, stratified layering introduces vertical heterogeneity, resulting in not only greater spatial variability but also more complex structural responses. This complexity is further exacerbated by gravitational compaction, which gives rise to distinct fluid flow and solid deformation mechanics within each variably saturated layer and at the interfaces between layers-markedly differing from those observed in homogeneous, single-layer soils. The current study systematically addresses these key issues by developing a comprehensive flow-deformation formulation of poroelasticity that rigorously captures the conservation of mass and momentum within and between phases in a system of unsaturated, multi-layer unconsolidated sediments under time-invariant loading. A key innovation of this formulation is its robust incorporation of gravitational body forces, enabling the establishment of a physically-consistent boundary-value problem that ensures continuity-preserving conditions at layer interfaces. Furthermore, we derive two novel closed-form analytical expressions that, for the first time, quantify the final total stress and total settlement in such a soil system under the influence of gravitational body forces. To characterize the extent of this impact, we introduce a dimensionless parameter that provides a quantitative measure of gravitational effects. To further enhance our understanding of the theory, we conduct a series of numerical simulations on a duallayer soil system comprising sand overlying clay, with varying levels of water saturation. Our results demonstrate that, irrespective of the saturation levels examined, gravitational body forces exert a significantly greater influence on the lower clay layer than on the upper sand layer, particularly at lower water saturations. Neglecting gravitational body forces in a layered soil model leads to an underestimation of both the dissipation rate of excess pore water pressure and the total settlement. Notably, the discrepancy in final total settlement between models that include and exclude gravitational forces exhibits an approximately linear dependence on soil thickness.

The pile foundation construction adjacent to an operational subway tunnel can induce the creep effects of the surrounding soil of the tunnel, resulting in the deformation of the existing tunnel lining and potentially compromising the safe operation of the tunnel. Therefore, the Mindlin solution and the generalized Kelvin viscoelasticity constitutive model were employed to establish the theoretical calculation model for the deformation of the adjacent subway tunnel caused by the pile construction. Then, the effect of pile construction on the deformation of adjacent tunnels under different pile-tunnel spacing was analyzed via three-dimensional numerical simulation and theoretical calculation methods and compared with the field monitoring data. The results showed that the theoretical and numerical data are in agreement with the field monitoring data. The theoretical model provides closer predictions to the field-measured values than the numerical simulation. As the distance between the pile and the tunnel increases, both the vertical settlement and the horizontal displacement of the subway tunnel lining exhibit a gradual reduction. In the hard plastic clay region of Hefei City (China), pile foundation construction near an operational subway tunnel can be classified into three distinct zones based on proximity to the tunnel: the high-impact zone (3.0 D). The pile foundation in high-, moderate-, and low-impact zones should be monitored for 7 days, 3 days, and 1 day, respectively, to ensure the stable deformation of the lining.

An analysis for the torsional dynamic response of end-bearing pile foundations embedded in a layered transversely isotropic geomaterial (soil/rock) is presented. The deformation of the transversely isotropic soil or rock is described by the method of separation of variables. The elasticity theory for a viscoelastic medium with frequency independent hysteretic material damping, and the Extended Hamilton's Principle are utilised to derive the differential equations describing pile and soil motions. The differential equations are solved analytically in an iterative algorithm. The accuracy of the analysis is verified with existing studies reported in the literature for pile foundations embedded in a homogeneous and layered soil deposit. The effect of the degree of anisotropy on the pile-soil response - dynamic pile-head stiffness, distribution of pile rotation and torque with depth, dimensionless soil displacement function for various values of pile slenderness and pile-soil stiffness ratios in a homogenous soil deposit is investigated. Design charts of static pile-head stiffness in a homogeneous soil deposit for a wide range of pile-soil stiffness and pile slenderness ratios, and degree of anisotropy are also reported. The effect of soil layering for a pile embedded in a two-layered soil deposit is also studied.