International Journal of Geomechanics

An assessment of three-dimensional slope stability analysis methods in terms of safety factors using several idealized sliding masses composed of plane sliding surfaces was made. Three-dimensional safety factors were calculated and compared for different study cases considered in this study on the basis of the exact solution methods, the Hovland method, and the 3D simplified Janbu method. Parameters investigated in this study included the effect of water pressure, horizontal seismic force, the changing gradient of a sliding surface, the changing lateral gradient of a sliding surface, and anchor force. Results showed that the Hovland method gives smaller safety factor values compared to the exact solutions, especially in cases of narrow failure width and high water pressure along sliding surfaces whereas the 3D simplified Janbu method gives the same safety factor values as the exact solutions

This paper presents the study of negative skin friction of the superlong pile caused by the soil settlement under large-scale surcharge loading. Based on the displacement equilibrium principle and transfer matrix method, with the introduction of a load transfer model considering shaft resistance softening, the analytical model of negative skin friction of superlong pile under surcharge loading is established by considering the three-dimensional consolidation settlement along the pile under surcharge loading, the compression deformation of pile, and the soil settlement around pile-end. Three-dimensional Biot consolidation is used to derive the settlement of soil surrounding pile and the settlement formula is simplified by using the Laplace and Hankel integral transform. Furthermore, the analysis is conducted for an engineering example using the theoretical model and FEM simulation method. The results are also compared with the corresponding measured data. The characteristics of negative skin friction of superlong pile under surcharge loading are obtained, and the effect of soil parameters on negative skin friction is discussed as well, which can offer valuable reference for the design of superlong piles.

Meshfree method is one of the numerical methods that typically use higher-order approximate functions and a weighted-residual approach to formulate the shape functions that are independent of the grids. In this paper, a series of computational modeling were conducted using the meshfree local Petrov-Galerkin (MLPG) method to evaluate the bearing capacity and response behavior of extended-length piles. The computational program codes and boundary conditions were generated based on the elastic-plastic behavior of the surrounding soil, reinforcements, and the noncontinuous interfaces between the piles and the soil. Compared to the traditional finite-element method (FEM), the MLPG exhibited higher accuracy in the results and indicated that the optimal length of the pile is directly related to the stiffness of the soil, i.e., the stiffer the soil, the longer the allowable pile length. Overall, the MLPG meshfree method was found to be a reliable and potentially promising numerical method for studying the bearing behavior of pile foundations.

Anchor foundations of various embedment ratios, shapes, and sizes are frequently used in civil engineering structures to provide uplift resistance. Therefore, to achieve economic and safe design of such foundations, engineers should understand the failure mechanism associated with them. In the present study, a three-dimensional (3D) finite element model incorporating an elastoplastic material model coupled with the isotropic strain-softening law, the nonassociated flow rule, and the shear-band effect, is used to investigate the failure mechanisms of vertically uploaded shallow rectangular anchor foundations buried in dense Toyoura sand. Satisfactory agreement was found between the experimental and numerical uplift resistance-displacement factor relationships. In particular, the peak uplift resistance, response stiffness, and passive plastic zone development are found to be functions of the embedment ratio, shape, and size. However, previous design approaches cannot capture the size effect on the peak uplift resistance factor of the rectangular anchor foundation.

An estimation of the runway pavement deflection during landing for design purposes has been a challenging problem for engineers. This paper presents a simple analytical model to predict dynamic deflection of a runway pavement at touchdown point caused by a landing gear load during aircraft landing. Three independent parameters, modulus of subgrade reaction ($k_s$), contact pressure ($p$), and vertical component of aircraft velocity ($v_v$), are required to estimate the deflection using this model. This model shows that the dynamic deflection increases with an increase in vertical velocity and contact pressure. These observations follow an expected trend and the field observations made during inspection of the runways. Likewise, the impact factor, which is defined as the ratio of the dynamic deflection to static deflection, also increases with an increase in vertical velocity for a given value of the contact pressure. Irrespective of contact pressure values, the impact factor for zero vertical velocity is 2 under elastic runway pavement conditions. An illustrative example is presented to explain the use of model expressions as well as the use of graphical presentations as design charts for calculating the dynamic deflection and associated impact factor.

Laboratory model tests in geotechnical engineering are routinely performed in small concrete or steel test tanks to examine the bearing capacity of footings, lateral earth pressures on retaining walls, behavior of reinforced foundation soils, and more. Results from these model tests are influenced by the shear forces generated on the sidewalls. The influence of such extraneous forces may completely change the interpretation of the test results or the failure mechanism. This paper presents a methodology for assessing the influence of such sidewall forces through numerical simulations. Through systematic numerical simulations, the influence of factors such as the relative size of the test tank, soil properties, and sidewall properties as investigated. The influence of sidewall friction and relative size of the test tank on the results as also investigated. Sidewall friction was found to a lesser effect for a wider test tank or for soil with a greater friction angle. Some recommendations on the relative tank sizes are also made on the basis of the results of this investigation.

Application of the smoothed particle hydrodynamics (SPH) method to the simulation of granular materials under large deformation is presented. The Drucker–Prager constitutive model with nonassociated flow rule is implemented in the SPH formulations to model granular flow in a continuum framework. The model developed is validated by experiments on the collapse of two-dimensional granular columns as reported in the literature. Simulations of the collapse of three-dimensional axisymmetric sand columns with various aspect ratios are also conducted. Numerical results of the granular flow pattern, final runout distance, final deposit height, and nondeformed region are in good agreement with the experimental observations as reported in the literature. It is suggested that despite being a continuum-scale model, the SPH model developed can be used to effectively simulate large deformation and dense flow of granular materials, and geomaterials in general, if proper constitutive models are implemented. The model developed may thus find applications in various problems involving dense granular flow and large deformations, such as landslides and debris flow.

Most of the municipal solid waste (MSW) landfills can fail in different modes such as sliding, rotational, or translational mode under both static and seismic loading conditions. These landfills constructed in the seismic zones experience additional seismic inertial forces in both horizontal and vertical directions during earthquakes. The conventional pseudostatic method of analysis suffers from major limitations by not considering the dynamic nature of forces such as variation of seismic inertial forces with time, frequency and the effects of shear and primary waves in the analysis. The scope of this paper is to present the application of the modern pseudodynamic method for evaluating seismic stability of MSW landfills by using a translational failure mode. In the present analysis, closed-form solutions are developed for upper and lower ranges of the factor of safety against translational failure and the yield acceleration by using the limit equilibrium method for pseudodynamic forces. A parametric study is performed to evaluate the influence of variation of different parameters, such as backfill and face slopes, base inclination, soil friction angle, the interface friction angle, and the ratio of top width-to-height of landfill, on the factor of safety and the yield acceleration. The results obtained are compared with the static translational failure analysis results available in the literature.

An exponential creep model on the basis of material properties degradation law was applied in the paper to simulate the rheological behavior of inhomogeneous rock and time-dependent response of rock tunnels. The primary, secondary, and tertiary creep regimes associated with damage were observed in the simulations, indicating that the macroscopic creep failure is linked to clusters of microstructure damage evolution at a mesoscale. Simulations on the time-dependent response of tunnels in the long-term under different coefficients of lateral pressure show that creep deformation and damage occurs in rock mass at tunnel sidewalls around rock mass under the coefficient of lateral pressure less than unity, whereas creep deformation and damage occurs at the roof and floor of the tunnel under the coefficient of lateral pressure larger than unity. Under the hydrostatic pressure of the coefficient of lateral pressure equal to unity, creep deformation and damage randomly occurs and damage localization forms and failure occurs at weak zone of the tunnel. Furthermore, tunnel closure displacements of the tunnel wall along the horizontal direction under three coefficients of lateral pressure are directly proportional to the coefficients of lateral pressure. Tunnel closure will be a maximum in the maximum principal stress direction and a minimum perpendicular to it for the coefficients of lateral pressure differing from unity.

This paper investigates the main parameters that affect the propagation of a fluid driven-fracture in a poroelastic medium. The fracture results from the pumping of an incompressible Newtonian viscous fluid at the fracture inlet, and the flow in the fracture is modelled by the lubrication theory. Rock deformation is assumed as porous-elastic. Leak-off in the host rock is considered to account for the diffusion effects in the surrounding formation. The propagation criterion is of the cohesive type. Finite element analysis was performed to compute the fracturing pressure and fracture dimensions as a function of the time and length. It was found that higher pressures are needed to extend a fracture in a poroelastic medium than in an elastic medium, and the created profiles of poroelastic fracture are wider. It was found that grain compressibility plays a minor role and does not result any significant difference in the fluid pressures and fracture dimensions. Wider fracture profiles are obtained with higher injection rates. The fluid pressures and the fracture apertures are larger in the case of a high permeability formation.

Saturated sparsely fractured granite (average fracture spacing on the order of meters) is currently studied as the host rock for a potential high-level nuclear waste repository in China. As part of an effort to study the coupling of waste-decay induced heat conduction in the rock matrix and heat convection in the fractures, a mathematical model is proposed for two-dimensional advective-conductive heat transfer in sparsely fractured water-saturated rocks with heat source(s), and an integral-equation solution scheme is developed by using discrete Laplace transform and numerical integration. The model and solution procedure is verified against an analytical solution for a single-fracture case with 1D perpendicular-to-fracture heat conduction. Illustrative calculations reveal, among other things, that significant interactions exist between the heat source intensity and the locations, apertures, and water velocities of the fractures, and that the influence of water in the fractures on the temperature in the rock matrix increases with the magnitudes of the fracture apertures and the water velocities.

In this study, three-dimensional finite element models, incorporating an elastoplastic material model coupled with isotropic simple softening law, nonassociated flow rule, and shear-band effect, are validated for the evaluation of the shape effect of the square and rectangular vertically uploaded anchor foundations embedded in dense Toyoura sand with embedment ratio of 2 and width of $50\mathrm{mm}$. The proposed numerical model has closely predicted experimental uplift load-displacement relationships. The shape effects on the results are also discussed in relation to the progressive failure around the foundations and the shape of the failure boundaries on the ground surface.

The failure anisotropy of geomaterial is inherently related to the microstructure such as grain arrangement, bedding, and crack pattern. This paper presents a formulation of an anisotropic failure criterion in three-dimensional (3D) stress space on the basis of the combination of the SMP criterion and a material microstructure tensor proposed in previous publications. The criterion is specialized for cross-anisotropic granular-material based on the loading direction and the direction of material bedding determined by two angles in 3D stress space. Consequently, it can describe the variation of strength resulting from the changing of the direction of material bedding and the changing of the stress state. Furthermore, the proposed criterion can capture the cross-anisotropic strength behavior of granular materials, which is concluded from the comparisons between its predicted and relevant experimental results.

Drilling and blasting method has been used for many years in underground excavations and still is very popular because of its many advantages. Blast performance is ordinarily measured by specific charge and by explosive consumption of broken rock. The empirical models are available for estimation of specific charge and different sets of parameters. This paper presents the possibility of applying artificial neural networks (ANNs) to estimate the specific charge in various conditions of tunnel blasting. Among available existing parameters in the literature, some of the most influencing parameters are selected. After running different models, $P$ wave, rock-quality designation (RQD), tunnel area, maximum depth of the hole, and coupling ratio (charge-to-hole diameter) are selected to estimate specific charge of tunnel blasting under various conditions. Also, conventional multi variable linear regression analysis (MVLRA) is applied to estimate specific charge. The results show that the accuracy of ANN is more than the MVLRA-based models.

This paper aims to study the dispersion of torsional surface waves in a self-reinforced layer over a half-space with linearly varying rigidity and density. Dispersion equation has been obtained in closed form. Dispersion relation for isotropic layer lying over a heterogeneous half-space has been deduced. As a result, the velocity equation for reinforced layer over a half-space of constant density has also been obtained. It has been observed that for isotropic upper layer over a homogeneous half-space, the velocity of torsional surface waves coincides with that of Love waves. This study shows that the increment in inhomogeneity decreases the phase velocity but the presence of reinforcement increases it significantly. Effects of different inhomogeneity parameters on the phase velocity have been depicted by means of graphs. Dispersion curves have been plotted for both reinforced and reinforcement free cases.