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Tensile cracks significantly influence stability of mining, tunneling, and other geotechnical engineering scenarios. Discontinuous deformation analysis (DDA) is widely employed to analyze, predict, and prevent the deformation and progressive failure of such geomaterials. However, an accurate and efficient simulation of the cracking process remains a challenge, requiring appropriate fracture models. This study presents an improved DDA algorithm featuring a nonlinear cohesive zone model (CZM) designed for the intricate deformation and fragmentation analysis of geotechnical structures composed of quasi-brittle materials. Building upon fracture mechanics theory, an exponential-type CZM that accounts for both post-peak softening behaviors and nonlinear relations inherent in quasi-brittle materials is introduced. This exponential-type CZM is integrated into the original DDA method, addressing the co-edge blocks connected with cohesive springs. The ensuing unbalanced force in normal contact arising from the nonlinear cohesive spring is mitigated using a nonlinear iterative algorithm. The formulation, the implementation, and the iteration of the exponential-type CZM within the DDA framework are elucidated. Finally, the feasibility and the accuracy of the improved DDA for analyzing quasi-brittle crack propagation are demonstrated and validated by comparing several examples with experimental and numerical results. Highlights: An improved DDA, incorporating an exponential-type CZM, is presented to simulate the nonlinear fracture behaviors in geomaterials. A nonlinear iterative algorithm is proposed to address the solution of nonlinear equilibrium equations in the improved DDA. The effectiveness and the accuracy of the improved DDA are validated and verified through typical examples. [ABSTRACT FROM AUTHOR]

A simplified numerical method was proposed for computing the slip-line field, as well as the associated earth-pressure coefficient, in a cohesionless backfill with an inclined surface lying behind an inclined rough wall. The potential failure zone, in either active or passive cases, was divided into the Rankine zone, which was rigorously obtained by the theory of plasticity, and the transition zone being further divided into a series of triangular slices. Within the transition zone, the theoretical relationship between the inclination of the interslice force and that of the slip surface was established by satisfying the Mohr–Coulomb failure criterion, and equations involving the forces on a typical slice were formulated in accordance with the force and moment equilibrium conditions. An iterative procedure was presented for computing the lateral forces on the wall by adjusting the inclination of the slip surface until the stress condition on the upper boundary of the transition zone was satisfied, resulting in the two families of slip lines. Several examples demonstrate the slip-line field configurations, and the computed earth-pressure coefficients were found to agree fairly well with those of other numerical methods. The determination of earth pressures and the associated critical failure surface play an important role in the design of retaining walls and other problems of geotechnical engineering. Conventional methods are frequently used for this purpose, but the errors involved are sometimes unacceptably large in cases of inclined rough walls. Hence, certain numerical methods have been employed, which, despite their sophistication, have not yet approached exact solutions. This paper presents a simplified numerical procedure for approaching theoretical slip-line fields and earth-pressure coefficients for the most frequently encountered cases of inclined rough walls with inclined cohesionless backfills. With this method, no assumptions need to be made about the shape of the slip surface or the inclinations of the forces acting on the boundaries of the triangular slices, into which the potential slip zone is divided. Furthermore, both the stress equilibrium condition and the Mohr–Coulomb criterion were completely satisfied within the failure zone and on its boundaries. An effective iterative procedure was provided for determining the slip surface location, which converged rapidly, resulting in an approximately theoretical configuration of slip-line field and associated earth-pressure coefficient values if a sufficiently large number of triangular slices were employed. [ABSTRACT FROM AUTHOR]

Soil structure is an important mechanics property which has drawn much attention from researchers. A piecewise‐linear numerical model, called SCS, is developed to investigate the large strain consolidation of structured soils. SCS accommodates large strain, soil self‐weight, vertical flows, time‐dependent loading, unloading/reloading, seepage force, soil heterogeneity, and soil structure. A three‐stage formulation is proposed to specify the compressibility behaviors of structured soils in SCS. The accuracy of SCS in the cases of small strain and large strain is checked comparing with analytical solutions and numerical solutions respectively. The effect of the main factors impacting soil structure on the consolidation processes of structured soils is investigated using several SCS simulations. Finally, a few SCS simulations with multiple structured soil layers are conducted. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The 2008 Mw7.9 Wenchuan earthquake in China caused widespread soil liquefaction and ground failures. A liquefaction case study of gently sloping ground at Yingxiu Town in the near-fault region is presented, which features its relatively thick deposits of sand-gravel mixtures, high soil stiffness, extremely intensive ground motion, large lateral spreading and severe damage of superstructure. The details of ground motion, site condition, field manifestations of liquefaction, subsurface soil profiles and field testing of shear wave velocities are presented. A conceptual binary mixture model is proposed to explain the gravel content effect on the stiffness and liquefaction resistance of gravelly soils. A preliminary liquefaction triggering evaluation method for gravelly soils is proposed by considering the gravel content correction of shear wave velocities based on the existing simplified procedure for typical sandy soils. The failure mechanism of the Baihua Bridge built at this site is explored, and the liquefaction-induced lateral spreading in down-slope direction might aggravate the failure process by imposing a large kinematic load on the piers besides the inertial forces transferred from the superstructure. [ABSTRACT FROM AUTHOR]

Estimating the possible region of liquefaction occurrence during a strong earthquake is highly valuable for economy loss estimation, reconnaissance efforts and site investigations after the event. This study identified and compiled a large amount of liquefaction case histories from the 2008 Wenchuan earthquake, China, to investigate the relationship between the attenuation of seismic wave energy and liquefaction distance limit during this earthquake. Firstly, we introduced the concept of energy absorption ratio, which is defined as the absorbed energy of soil divided by the imparted energy of seismic waves at a given site, and the relationship between the energy absorption ratio and the material damping ratio was established based on shear stress-strain loop of soil element and the seismic wave propagation process from the source to the site. Secondly, the threshold imparted seismic energy of liquefaction was obtained based on existing researches of absorbed energy required to trigger liquefaction of sandy soils and the ground motion attenuation characteristics of the 2008 Wenchuan earthquake, and the liquefaction distance limit of this earthquake was estimated according to the proposed magnitude-energy-distance relationship. Finally, the field liquefaction database of 209 sites of the 2008 Wenchuan earthquake was used to validate such an estimation, and the field observed threshold imparted seismic energy to cause liquefaction in recent major earthquakes worldwide was back-analyzed to check the predictability of the present method, and several possible mechanisms were discussed to explain the discrepancy between the field observations and the theoretical predictions. This study indicates that seismic energy attenuation and liquefaction distance limit are regional specific and earthquake dependent, and 382 J/m3 is the average level of threshold imparted seismic energy to cause liquefaction for loose saturated sandy soils, and the corresponding liquefaction distance limit is approximately 87.4 km in fault distance for a Mw = 7.9 event in the Chengdu Plain. The proposed regional energy attenuation model and threshold imparted seismic energy may be considered as an approximate tool in evaluating the liquefaction hazard during potential earthquakes in this area. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Central South University is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Zhejiang University: Science A is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Liquefaction-induced large deformations of shallow foundations were widely observed during strong earthquakes, and one important feature of these is that they occur relatively slowly compared to the duration of earthquake shaking. As most previous model tests used clean sands with high permeability, this type of “delayed” failure mode has not been observed or reproduced realistically in the laboratory to date. In this study, a dynamic centrifuge model test was performed under 30 g to study the mechanism of post-liquefaction progressive failure of buildings with shallow foundation on relatively thick deposits of liquefiable sandy soils. A two-dimensionally asymmetrical model structure was used to simulate the eccentric loads at the interface between the foundation and the subsoil. A clayey sand model with a relative density of 35% was prepared to have the relatively low permeability and coefficient of consolidation comparable to those of in-situ sandy soils. A prototype 2 Hz, 80 s long sine sweep with peak amplitude of 300 gal was used to simulate an earthquake strong enough to trigger a typical liquefaction state. Seismic responses in the liquefiable deposits and deformations of the structure were monitored during and after shaking. The main finding of this study is that the post-liquefaction progressive failure of shallow foundation was due to the large ground deformation of subsoil where significant shear strain localization had developed during liquefaction. Progressive settlement and tilting of shallow foundation will continue as long as the liquefaction state maintains, and longer durations of liquefaction lead to larger deformations. [ABSTRACT FROM AUTHOR]

Based on consolidation equations proposed for unsaturated soil, an analytical solution for 1D consolidation of an unsaturated single-layer soil with nonhomogeneous mixed boundary condition is developed. The mixed boundary condition can be used for special applications, such as tests occur in laboratory. The analytical solution is obtained by assuming all material parameters remain constant during consolidation. In the derivation of the analytical solution, the nonhomogeneous boundary condition is first transformed into a homogeneous boundary condition. Then, the eigenfunction and eigenvalue are derived according to the consolidation equations and the new boundary condition. Finally, using the method of undetermined coefficients and the orthogonal relation of the eigenfunction, the analytical solution for the new boundary condition is obtained. The present method is applicable to various types of boundary conditions. Several numerical examples are provided to investigate the consolidation behavior of an unsaturated single-layer soil with mixed boundary condition. [ABSTRACT FROM AUTHOR]

Based on the Biot theory of porous media, the exact solutions to onedimensional transient response of incompressible saturated single-layer porous media under four types of boundary conditions are developed. In the procedure, a relation between the solid displacement u and the relative displacement w is derived, and the well-posed initial conditions and boundary conditions are proposed. The derivation of the solution for one type of boundary condition is then illustrated in detail. The exact solutions for the other three types of boundary conditions are given directly. The propagation of the compressional wave is investigated through numerical examples. It is verified that only one type of compressional wave exists in the incompressible saturated porous media. [ABSTRACT FROM AUTHOR]

The incorrect deduction of equations in the research works devoted to the studies of transient stress in cylindrically orthotropic tubes and done by Kardomateas (Journal of Applied Mechanics, 1989, 1990) leads to the wrong results. The errata ( 1991) correct the deduction error, but do not give the right numerical results. All errors are corrected, and the Mathematica is adopted to solve the large argument problem for Bassel function. A theoretical solution of the transient thermal stresses in tubes with uniform form is presented, and a numerical example is studied. [ABSTRACT FROM AUTHOR]

Axisymmetric fundamental solutions that are applied in the consolidation calculations of a finitecaly clay layer with impeded boundaries were derived. Laplace and Hankel integral transforms were utilized with respect to time and radial coordinates, respectively in the analysis. The derivation of fundamental solutions considers two boundary-value problems involving unit point loading and ring loading in the vertical. The solutions are extended to circular distributed and strip distributed normal load. The computation and analysis of settlements, vertical total stress and excess pore pressure in the consolidation layer subject to circular loading are presented. [ABSTRACT FROM AUTHOR]

The virtual laminated element method (VLEM) can resolve structural shape optimization problems with a new method. According to the characteristics of VLEM, only some characterized layer thickness values need be defined as design variables instead of boundary node coordinates or some other parameters determining the system boundary. One of the important features of this method is that it is not necessary to regenerate the FE (finite element) grid during the optimization process so as to avoid optimization failures resulting from some distortion grid elements. The thickness distribution in thin plate optimization problems in other studies before is of stepped shape. However, in this paper, a continuous thickness distribution can be obtained after optimization using VLEM, and is more reasonable. Furthermore, an approximate reanalysis method named “behavior model technique” can be used to reduce the amount of structural reanalysis. Some typical examples are offered to prove the effectiveness and practicality of the proposed method. [ABSTRACT FROM AUTHOR]

According to the results of experiments on the municipal solid waste (MSW), a series of formula are deduced to calculate the leachate free-faced headline curve. By means of static and dynamic finite element method (FEM), the stability of a wasteland during earthquakes is analyzed. It is demonstrated that the positions of the most dangerous sliding surfaces during earthquakes are fairly stable. Based on the above findings, this paper developed the Newmark method by increasing the precision to reckon the permanent deformation of wastelands during earthquakes. The method presented in the paper is not only of great importance to instruct the anti-seismic design of wasteland, but also valuable to the design of ordinary dams and embankments. [ABSTRACT FROM AUTHOR]