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Although lithium–sulfur batteries are promising replacements for conventional lithium-ion batteries, their commercial applications have been limited due to issues such as polysulfide dissolution, volume variation, and low conductivity. To overcome these problems, we designed and hydrothermally synthesized a flower-like three-dimensional CoS/multiwall carbon nanotube (MWCNT) composite as the sulfur host material. The CoS and MWCNTs were tightly joined by chemical bonds to form a stable composite structure. The polar and catalytic CoS can promote the redox process and reduce the dissolution of polysulfides, while the flexible carbon nanotubes can buffer the expansion/shrinkage of the electrode during charging and discharging. CoS/MWCNT-S displays an excellent specific capacity (1120 mAh g−1, 0.1 C) and high capacity retention after 200 cycles (78%, 0.5 C).

In this paper, a three-dimensional time-dependent Riesz space-fractional diffusion equation is considered, and an alternating direction implicit (ADI) difference scheme is proposed, in which a weighted and shifted Grunwald difference scheme (see Tian et al. (2015) [33] ) is utilized for the discretizations of space-fractional derivatives, and a fractional-Douglas-Gunn type ADI method is utilized for the discretization of time derivative. The method is proved to be unconditionally stable and convergent with second-order accuracy both in time and space with respect to a weighted discrete energy norm. Efficient implementation of the method is carefully discussed, and then based on fast matrix-vector multiplications, a fast conjugate gradient (FCG) solver for the resulting symmetric positive definite linear algebraic system is developed. Numerical experiments support the theoretical analysis and show strong effectiveness and efficiency of the method for large-scale modeling and simulations. Finally, a linearized ADI scheme based on second-order extrapolation method is developed and tested for the nonlinear Riesz space-fractional diffusion equation.

The study on fluid-solid interaction in heterogeneous suspensions is essential for theoretical research and engineering practice. In this paper, a three-dimensional fully resolved SPH-DEM method is presented to model suspensions with non-Newtonian fluids and solid particles of arbitrary shape. The fluid phase is modelled using SPH with a regularized Bingham model, whereas aggregates with irregular shapes is modelled using a DEM method based on surface mesh representation. A simple unified hybrid contact method is proposed to model the SPH-boundary, SPH-DEM, DEM-DEM, and DEM-boundary interactions in a generalized fashion. Furthermore, GPU parallelization is employed to increase the numerical efficiency. The coupling method is validated using numerical examples including: (1) water-entry of a sphere, (2) Poiseuille flow of a Bingham material, (3) collapse of columns of irregular particles, and (4) gravity-driven heterogeneous flows with irregular particle shape. The simulation results indicate that the presented method is suitable for heterogeneous flows with irregular solid particles.

A surface mesh represented discrete element method (SMR-DEM) for granular systems with arbitrarily shaped particles is presented. The particle surfaces are approximated using contact nodes obtained from surface mesh. A hybrid contact method which combines the benefits of the sphere-to-sphere and sphere-to-surface approaches is proposed for contact detection and force computation. The simple formulation and implementation render SMR-DEM suitable for three-dimensional simulations. Furthermore, GPU parallelization is employed to achieve higher efficiency. Several numerical examples are presented to show the performance of SMR-DEM. It is found that on the particle level the method is accurate and convergent, while on the system level SMR-DEM can effectively model particle assemblies of various regular and complex irregular shapes.

Evidence is scant on the relative and attributable contributions of ambient temperature on stroke subtypes mortality. Few studies have examined modification effects of multiple greenness indicators on such contributions, especially in China. We quantified the associations between ambient temperature and overall, ischemic, and hemorrhagic stroke mortality; further examined whether the associations were modified by greenness.We conducted a multicenter time-series analysis from January 1, 2013 to December 31, 2019. we adopted a distributed lag non-linear model to evaluate county-specific temperature-stroke mortality associations. We then applied a random-effects meta-analysis to pool county-specific effects. Attributable mortality was calculated for cold and heat, defined as temperatures below and above the minimum mortality temperature (MMT). Finally, We conducted a multivariate meta-regression to determine associations between greenness and stroke mortality risks for cold and heat, using normalized difference vegetation index (NDVI), soil adjusted vegetation index (SAVI), and enhanced vegetation index (EVI) as quantitative indicators of greenness exposure.In the study period, 138,749 deaths from total stroke were reported: 86,873 ischemic and 51,876 hemorrhagic stroke. We observed significant W-shaped relationships between temperature and stroke mortality, with substantial differences among counties and regions. With MMT as the temperature threshold, 17.16 % (95 % empirical CI, 13.38 %-19.75 %) of overall, 20.05 % (95 % eCI, 16.46 %-22.70 %) of ischemic, and 12.55 % (95 % eCI, 5.59 %-16.24 %) of hemorrhagic stroke mortality were attributable to non-optimum temperature (combining cold and heat), more mortality was caused by cold (14.94 %; 95 % eCI, 11.57 %-17.34 %) than by heat (2.22 %; 95 % eCI, 1.54 %-2.72 %). Higher levels of NDVI, SAVI and EVI were related to mitigated effects of non-optimum temperatures-especially heat.Exposure to non-optimum temperatures aggravated stroke mortality risks; increasing greenness could alleviate that risks. This evidence has important implications for local communities in developing adaptive strategies to minimize the health consequences of adverse temperatures.

A μ(I) rheology–based avalanche flow model whose governing equations are established in a rectangular Cartesian coordinate system is proposed in this paper. The motivation is updating the term related to gradients of the depth-averaged pressure and extending the application of μ(I) rheology to natural avalanche simulation. The main advantage of the proposed method is that it captures the constitutive properties of the avalanche by introducing the μ(I) rheology. The main novelty of the present model that distinguishes other μ(I) rheology–based approaches is that the in-plane shear is not considered in our model (consistent with the traditional Savage–Hutter theory); thus, the μ(I) rheology only plays a part in describing the normal transverse stresses. Experimental example shows that the proposed model can predict the moving process of granular flow satisfactorily. Simulation of a natural case (the Ermanshan avalanche in China) demonstrates that the simulation can approximately reproduce real avalanches tolerably well.

BackgroundLocal governments in China took restrictive measures after the outbreak of COVID-19 to control its spread, which unintentionally resulted in reduced anthropogenic emission sources of air pollutants. In this study, we intended to examine the effects of the COVID-19 lockdown policy on the concentration levels of particulate matter with aerodynamic diameters of ≤1 μm (PM1), ≤2.5 μm (PM2.5), and ≤10 μm (PM10), nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), and carbon monoxide (CO) and the potential subsequent reductions in the incidence of ischemic and hemorrhagic stroke in Shandong Province, China.MethodsA difference-in-difference model combining the daily incidence data for ischemic and hemorrhagic stroke and air pollutant data in 126 counties was used to estimate the effect of the COVID-19 lockdown on the air pollutant levels and ischemic and hemorrhagic stroke incident counts. The avoided ischemic stroke cases related to the changes in air pollutant exposure levels were further estimated using concentration-response functions from previous studies.ResultsThe PM1, PM2.5, PM10, NO2, and CO levels significantly decreased by −30.2, −20.9, −13.5, −46.3, and −13.1%, respectively. The O3 level increased by 11.5% during the lockdown compared with that in the counterfactual lockdown phase of the past 2 years. There was a significant reduction in population-weighted ischemic stroke cases (−15,315, 95% confidence interval [CI]: −27,689, −2,942), representing a reduction of 27.6% (95% CI: −49.9%, −5.3%). The change in the number of hemorrhagic stroke cases was not statistically significant. The total avoided PM1-, PM2.5-, PM10-, NO2-, and CO–related ischemic stroke cases were 739 (95% CI: 641, 833), 509 (95% CI: 440, 575), 355 (95% CI: 304, 405), 1,132 (95% CI: 1,024, 1,240), and 289 (95% CI: 236, 340), respectively.ConclusionThe COVID-19 lockdown indirectly reduced the concentration levels of PM1, PM2.5, PM10, NO2, and CO and subsequently reduced the associated ischemic stroke incidence. The health benefits due to the lockdown are temporary, and long-term measures should be implemented to increase air quality and related health benefits in the post-COVID-19 period.

Short-term exposure to ambient PMCounty-specific incidence of stroke was obtained from health statistics in years 2014-2019. We linked county-level mean daily concentrations of PMThe study included a total of 2,193,954 stroke, from which 1,861,331 were ischemic and 332,623 were hemorrhagic stroke. PMPM

Variable-order time-fractional diffusion equations (VO-tFDEs), which can be used to model solute transport in heterogeneous porous media are considered. Concerning the well-posedness and regularity theory (cf., Zheng & Wang, Anal. Appl., 2020), two finite difference ADI and compact ADI schemes are respectively proposed for the two-dimensional VO-tFDE. We show that the two schemes are unconditionally stable and convergent with second and fourth orders in space with respect to corresponding discrete norms. Besides, efficiency and practical computation of the ADI schemes are also discussed. Furthermore, the ADI and compact ADI methods are extended to model three-dimensional VO-tFDE, and unconditional stability and convergence are also proved. Finally, several numerical examples are given to validate the theoretical analysis and show efficiency of the ADI methods.

A stabilized coupled total-Lagrangian and conventional Euler kernel based smoothed particle hydrodynamics (TL-CE SPH) method is presented to model three-dimensional granular flow-structure interaction with rigid and deformable structures. In the coupled TL-CE SPH, the granular material is simulated using CESPH with the Dracker-Prager model, while the structure solver is based on TLSPH. The stabilized TLSPH with corrected kernel gradient, Lagrangian kernel function and hourglass control technique overcomes the common deficiencies of inconsistency, tensile instability and hourglass mode in structure modeling. Based on the Adami boundary condition (Adami et al., 2012), a unified framework for modeling solid boundaries and the granular media-structure interfaces is presented. Furthermore, the advanced GPU-acceleration is employed to achieve high efficiency. The coupled method is employed to simulate problems of granular collapse, granular material-structure interaction at quasi-static regime and granular flows impact on rigid and deformable structures. The presented method can simulate granular flows, the flow-structure interactions, and the deformation and stress of the structures correctly. Furthermore, the GPU-acceleration gives hundreds times of speed-up over serial CPU implementation. The presented method can be applied to large scale three-dimensional cases.

A coupled total Lagrangian (TL) and weakly compressible (WC) smoothed particle hydrodynamics (SPH) method is presented to model three-dimensional fluid–structure interactions (FSI) with deformable structures. In the coupled TL–WC SPH, the fluid phase is simulated using WCSPH, while the structure solver is based on TLSPH. The three main deficiencies of solid simulation using conventional SPH, i.e. inconsistency, tensile instability and hourglass mode are circumvented in the stabilized TLSPH by means of corrected kernel gradient, Lagrangian kernel function and hourglass control technique, respectively. The resulted stabilized TLSPH is stable, accurate and has almost quadratic convergence rate in solid modeling. To increase the accuracy in FSI modeling, the δ − SPH technique is employed to improve the pressure results in the fluid phase. Based on the Adami boundary condition (Adami et al., 2012), a unified framework for modeling solid boundaries and the fluid–structure interfaces is presented. Furthermore, the GPU parallelization is employed to accelerate the proposed TL–WC SPH method for higher efficiency. The coupled method is employed to simulate problems of pure fluid flow, elastic solids with large deformation and fluid–structure interaction with deformable structures. The numerical results are compared with analytical solutions and results from literature. The GPU efficiency and speed-up compared with CPU implementations are analyzed. The novelty of this work consists: (1) three-dimensional SPH modeling of FSI problems with deformable structures, (2) stabilized structure simulation free of hourglass mode, (3) a unified framework for FSI problems taking advantages of δ -SPH, TLSPH, hourglass control, and GPU acceleration. Importantly, with the hourglass control technique proposed by Ganzenmuller (2015), stresses can be captured accurately in the TL–WC SPH-based FSI simulations.

Essential amino acids (EAAs) are involved in growth and development in children and adolescents. This study was aimed at exploring the relationship between dietary EAA intakes and metabolic biomarker, and the influence of obesity in children and adolescents. A total of 3566 subjects were analysed. Participators were classified according to weight status. Metabolic biomarkers were determined using standardized methods and conditions. Normal, overweight, and obesity statuses were defined according to the Working Group on Obesity in China (WGOC) BMI cutoff points based on age- and sex-specific screening criteria. In normal-weight group, blood uric acid was negatively correlated with dietary Ile, Leu, Lys, Phe, Thr, Val, and His, and zinc was negatively correlated with Ile, Leu, Lys, Phe, Thr, Val, His, Met, and Trp. In overweight group, TC was negatively correlated with Ile, Leu, Phe, Val, and His, and LDL-C was negatively correlated with Ile, Leu, Lys, Phe, Thr, Val, His, and Met, while TG was positively correlated with Leu, Lys, Phe, Thr, Val, and Met. In obesity group, hemoglobin was positively related to Ile, Leu, Lys, Phe, Thr, Val, His, and Trp, while vitamin D was positively correlated with His and Trp. The serum creatinine was negatively correlated with Ile, Leu, Phe, Val, His, and Met in normal-weight group, and positively correlated with Ile, Leu, Lys, Phe, Thr, Val, His, Met, Trp, His, and Trp in obesity group. Dietary amino acid score (AAS) and Leu intake were protective factors for obesity. The association between fasting blood glucose and EAAs intake was weak and labile. Metabolic biomarkers and EAA intakes were only related under certain weight status. The dietary AAS is positively correlated with HDL-C, LDL-C, serum creatinine, albumin, serum vitamin D, and zinc. The subtle relationship of EAAs and kidney function should be explored further. There is a complex relationship between EAAs and metabolic biomarkers, and overweight and obesity have a certain influence on this relationship.

Due to huge bulk volume and extremely complex geometrical and geological features, it is forbiddingly difficult to perform a dam structural analysis with even moderate geometry fidelity in engineering practices. We present a high resolution of engineering structural analysis of the first ultra-high concrete-faced rockfill dam in China. Mesh resolution is taken to be 20 cm along slab thickness for the bulk volume of 20M $$\hbox {m}^{3}$$ of the whole dam. The engineering problem is solved by considering nonlinear behaviors such as joints’ contact nonlinearity, creep deformation, and strong thermo-mechanical coupling, as well as blended continuous-discontinuous approximation, on a mesh model of 1.1 billion dofs using 16K CPU cores of Tianhe-II. The problem to be solved is a challenging non-positive definite, non-symmetric and ill-conditioned matrix problem. The simulation confirms in the first time that the sunlight temperature effect can contribute up to a contact stress increment of maximum 10.9 MPa and explains frequent extrusion damage observed for the dam. As model tests are difficult to perform for high dams, with this first success, we envision that extreme-scale simulation would pose broad impact on the safety evaluation of high dams in future.

The lithium-sulfur (Li-S) battery has received widespread attention because of the high theoretical energy density and inexpensive raw material. However, some issues still restrict its commercialization, including the shuttle effect, the lithium dendrite growth and low safety, etc. In this work, a PMMA-LLZO/PP/AB multifunctional separator was designed and facilely prepared to overcome these problems. A composite dense layer of the PMMA and LLZO sheets with excellent interface stability was coated on one side of the PP separator to face lithium metal anode, which can inhibit the lithium dendrites growth and increase the safety. Meanwhile, this composite coating possesses high affinity with the liquid electrolyte and the soluble polysulfides, which can improve the ionic conductivity, effectively adsorb the polysulfides. An acetylene black (AB) layer was further coated on the other side of the PP separator to not only act as an electron conductor but also adsorb and hinder the migration of lithium polysulfides. The co-modified PMMA-LLZO/PP/AB separator displays remarkable electrochemical performances and an excellent thermal stability. The cell with the co-modified separator exhibits high specific capacities of 1456 mAh g−1 at 0.1 C and 969 mAh g−1 at 1.0 C, and retains a capacity of 413 mAh g−1 after 500 cycles, corresponding to a retention of 42.6% as well as a low decay of 0.114%/cycle. Especially, the cell with the multifunctional separator also displays a high capacity and a low decay even for a high sulfur mass loading cathode of 2.5–3.0 mg cm−2 or at a high temperature of 60 °C. The co-modified multifunctional separator has great application potential in the high-performance Li-S battery.

Traixial test is a common method for the study of the mechanical behaviors of granular materials. And, the interaction between the membrane and particles will greatly influence the test results. In this paper, computational contact mechanics method is developed for the simulation of sphere-sphere and sphere-membrane contacts in triaxial test. In both algorithms, the contact state and distance functions are determined according to the geometric information of the spheres instead of the finite element mesh. Two benchmarks have been used to validate the proposed algorithms, and the results showed that the sphere-sphere and sphere-membrane interactions were accurately and stably simulated. Furthermore, the size of the spherical particle elements has minor influence on the numerical results and therefore, it can be used for the study of the granular mechanics with larger number of particles. Finally, the consolidation process of a triaxial test is studied and compared with the laboratory tests, which also shows that the algorithm can not only better simulate the membrane penetration process but also the meso mechanics of the granular materials.

Extrusion damage in the concrete face was widely observed in high concrete-faced rockfill dams in the last two decades. However, the accurate estimation of the concrete stress remains a great challenge. In this paper, a thermo-mechanical coupling method is presented to numerically evaluate the solar radiation effect on the concrete stress within the dual mortar finite element framework. The heat conduction is modelled as a transient time-dependent equation and hence the heat flow can be determined by meteorological data. The thermo-mechanical coupling is conducted in a weak way such that the linear system can be split into two subsystems friendly to the linear solver. The present method based on using nonconforming meshes is validated by the comparisons with node-to-segment method, conforming mesh and analytical solution. The application to a concrete-faced rockfill dam indicates that the phase lag and amplitude damping effects are apparent in the thermal analysis, confirming the importance of using transient heat conduction theory. The observed slab-slab separations emphasis the importance of using dual mortar contact method. The thermal stress is found to be larger than 10 MPa and therefore needs to be considered in the design and safety assessment.

In the construction of high concrete-faced rockfill dams (CFRDs), soft filler is used in the longitudinal joints in order to avoid extrusion damage to the concrete face slab. In this paper, we consider the soft joint contact as an equivalent contact interface to avoid introducing conventional elements. Based on the introduction of a general transformation to obtain fully decoupled contact constraints, a new generalized node-to-segment formulation is developed to solve the multi-body contact problem in CFRDs. The high CFRD of Tianshengqiao-1 in China is numerically analyzed; the results show that soft joints can significantly reduce the axial stress of face slabs.

In this paper, a flow model for avalanches based on the three-dimensional yield criterion is presented in an attempt to allow the relaxation of the assumption of lateral confinement pressure that is adopted in the traditional three-dimensional Savage–Hutter model (S–H model). One of the advantages of this model is that a simplified constitutive relationship for granular flow, which could reveal the internal mechanism of avalanches, is adopted. Additionally, another advantage is that the strength parameters used in the proposed model are readily available for natural materials. The flow properties of avalanches are influenced by the generalized friction coefficient, which is a parameter that can be assessed by introducing the three-dimensional yield criterion. By comparing the results obtained by numerical simulations using the model proposed in this paper and laboratory experiments, a reasonably good agreement can be reached with regard to the prediction of the moving process of avalanches.

Conventional two-field mortar methods have master/slave bias and need special treatments for the cross corner problem. In this work, we present a three-field dual mortar method, which employs an intermediate interface to connect individual subdomains with nonconforming meshes. Using this intermediate interface as the master face, a dual mortar method can be formulated by discretizing Lagrange multipliers on the subdomain interfaces using dual basis functions. Furthermore, the computational cost is minimized by static condensation of Lagrange multipliers and elimination of displacement unknowns on subdomain interfaces. Owing to the three-field formulation, the presented method is free of master/slave bias and can handle the cross corner problem naturally. The stability condition for the intermediate interface mesh is investigated by theoretical analysing and numerical modelling. Numerical tests show that the presented method has optimal convergence rate and allows great flexibility in mesh preparation.

This study aimed to explore whether the depression of offspring caregivers can be affected by the intergenerational disagreements on preferred living arrangements for the elderly, and the extent of this influence.A total of 875 participants from five urban neighborhoods were investigated in a cross-sectional survey in Jinan, China. Depressive symptoms were assessed by the Self-rating Depression Scale (SDS). Multiple stratification was performed based on participants' characteristics, then generalized linear models (GLM) were used to adjust confounding factor and analyze the effect of the intergenerational disagreements on depressive symptoms among participants with different characteristics.The intergenerational disagreements on preferred living arrangements for the elderly greatly impact on offspring caregivers' depressive symptoms. Especially in the following two situations: (1) in the case of older adults were relatively independent and offspring caregivers had to co-reside with older adults against their own will, the max mean difference on the depression measures was up to 10.603 (p0.001), in comparison with both parties were willing to co-reside. (2) In the case of older adults were fully dependent and offspring caregivers had not to hire a maid to care older adults against their own will, the max mean difference on the depression measures was up to 8.937 (p0.001), in comparison with both parties were willing not to hire a maid.Intergenerational disagreements on preferred living arrangement for the elderly have negative effect on offspring caregivers' depressive symptoms.

In this paper, we analyze the constitutive laws of a hydraulic dynamic model, the Savage–Hutter (S–H) model, and the Hungr model. To overcome their limitations, we adopt a frictional viscoplastic constitutive law for dense granular flow and propose a new constitutive law-based dynamic model for avalanches by simplifying the internal stresses for shallow granular flow. The range of the earth pressure coefficient in each model is studied and compared. Finally, we compare the previous experimental results with those obtained from the proposed model and the S–H model, and we find that the new model can capture the flow properties of an avalanche.

In terms of \(L_{1/2}\) regularization, a novel feature selection method for a neural framework model has been developed in this paper. Due to the non-convex, non-smooth and non-Lipschitz characteristics of \(L_{1/2}\) regularizer, it is difficult to directly employ the gradient descent method in training multilayer perceptron neural networks. A smoothing technique has been considered to approximate the original \(L_{1/2}\) regularizer. The proposed method is a two-stage updating approach. First, a multilayer network model with smoothing \(L_{1/2}\) regularizer is trained to eliminate the unimportant features. Second, the compact model without regularization has been simulated until there is no improvements for the performance. The experiments demonstrate that the presented algorithm significantly reduces the redundant features while keeps a considerable model accuracy.

The safety issues of geotechnical structures are often related to tension-induced cracking of geomaterials. Conventional finite element analysis often experiences difficulties in re-meshing and adaptively analyzing the crack propagation region. In this work, the Radial Point Interpolation Method (RPIM) is adaptively coupled with the Finite Element Method (FEM) to simulate tensile crack initiation and propagation in earth structures. In the algorithm, FEM mesh in identified crack regions is automatically converted to RPIM nodes and then refined for crack analysis. The behavior of soil under tension and the brittle and quasi-brittle failure types are investigated based on typical tensile test results. Especially, the crack-induced anisotropic and softening behaviors of soils are appropriately simulated using the smeared crack approach. Two types of soil cracking experiments, the four-point bending test and centrifuge model test, were conducted in the laboratory and simulated by the proposed approach. Good agreements between the simulated and experimental results have been obtained, which demonstrates the effectiveness of this coupled method for 2D and 3D simulations of tensile cracking in earth structures.

Summary Failure in geotechnical engineering is often related to tension-induced cracking in geomaterials. In this paper, a coupled meshless method and FEM is developed to analyze the problem of three-dimensional cracking. The radial point interpolation method (RPIM) is used to model cracks in the smeared crack framework with an isotropic damage model. The identification of the meshless region is based on the stress state computed by FEM, and the adaptive coupling of RPIM and FEM is achieved by a direct algorithm. Mesh-bias dependency, which poses difficulties in FEM-based cracking simulations, is circumvented by a crack tracking algorithm. The performance of our scheme is demonstrated by two numerical examples, that is, the four-point bending test on concrete beam and the surface cracks caused by tunnel excavation. Copyright © 2014 John Wiley & Sons, Ltd.

A point-loading device was used to research the breakage characteristics of single particles and to study their crushing mechanism. A series of point-loading tests were completed on the basis of cement ellipsoid particles modeled in various sizes and strengths with cement pastes. A close-packing method of equal spheres with several close-packed assemblies was generated, and the corresponding numerical models for cement ellipsoid particles were established by the discrete-element method. Experimental and numerical tests show that the high-strength materials are brittle, whereas the low-strength materials are ductile, and vice versa. A comparison of the experimental and numerical results show reasonable, rational results, and indicate that the force-displacement relationship is approximately linear for this type of granular material. A measurement-sphere method was used to trace the energy and stress distribution in the particle samples. The accumulation of dilatant deformation causes the collapse of the local skeleton structures in the cement ellipsoid particles.

This paper presents a general 3D contact smoothing method based on the meshfree radial point interpolation method to improve the numerical simulation of contact problems. In particular, a locally smooth contact surface is constructed from the scattered surface nodes by point interpolation using the combination of polynomial and radial bases. With such bases, this method reproduces smooth surfaces even for coarse meshes and the constructed surface passes exactly through the surface nodes. Results for contact problems involving deformable bodies are included to demonstrate its advantages.

Particles of natural rockfill materials come in various sizes and shapes, resulting from natural processes, and their mechanical properties are affected by a multitude of interdependent factors. As a result, it is very difficult to investigate an individual factor. Therefore, most studies are conducted by using substitute materials such as glass beads, gypsum rods, wooden rods, steel balls, and metal rods. However, these commonly used materials have properties that are often quite different from natural rockfill materials, e.g., in particle shape, particle strength, modulus, and grading. This paper suggests a more suitable substitute to simulate rockfill materials by using cement ellipsoids in different sizes cast with cement paste. Results from triaxial compression tests show that this kind of proxy material can reproduce the basic behavior of natural rockfill materials.

The parameters of the constitutive model, the creep model, and the wetting model of materials of the Nuozhadu high earth-rockfill dam were back-analyzed together based on field monitoring displacement data by employing an intelligent back-analysis method. In this method, an artificial neural network is used as a substitute for time-consuming finite element analysis, and an evolutionary algorithm is applied for both network training and parameter optimization. To avoid simultaneous back-analysis of many parameters, the model parameters of the three main dam materials are decoupled and back-analyzed separately in a particular order. Displacement back-analyses were performed at different stages of the construction period, with and without considering the creep and wetting deformations. Good agreement between the numerical results and the monitoring data was obtained for most observation points, which implies that the back-analysis method and decoupling method are effective for solving complex problems with multiple models and parameters. The comparison of calculation results based on different sets of back-analyzed model parameters indicates the necessity of taking the effects of creep and wetting into consideration in the numerical analyses of high earth-rockfill dams. With the resulting model parameters, the stress and deformation distributions at completion are predicted and analyzed.

Following the completion of triaxial compression tests on cement ellipsoid specimens, the particle size distribution for the specimen was analyzed after testing. It is found that neither particle strength nor confining pressure had much effect on the particle size distribution of completely broken particles. That is, the aggregates with different particle strengths have approximately the same fractal dimension. Hardin’s relative breakage was modified based on the concept of optimum distribution. Also, a relationship between relative breakage and plastic work was suggested and verified in this paper.

The variation of stress–strain state induces changes in the permeability of clayey soil and then affects the properties of seepage and consolidation. In previous studies, variations of the permeability of soil in shear process were mainly neglected, and there were no reasonable descriptions of the permeability in such a condition. To study the variation of the hydraulic conductivity of clayey soil in shear process, new triaxial seepage equipment was designed by changing the conventional triaxial apparatus. Based on a series of tests under different confining pressures carried out by this equipment, the influences of the stress–strain state of clayey soil on hydraulic conductivity were investigated. Furthermore, a mathematical model for the hydraulic conductivity of clayey soil under the condition of large shear deformation was proposed. The comparison between the seepage test results and the calculated values of the proposed model indicates that the mathematical model can calibrate the effects of ...

A consolidation analysis method for an earth-rockfill dam based on the coupling of physical state, stress deformation, and seepage was established. In this method, a permeability coefficient model considering physical state and shear stress level was introduced, and it was integrated with Biot’s consolidation theory to simulate the coupling relationship. Taking the Nuozhadu high earth-rockfill dam as an example, a parameter back-analysis method using a neural network and evolutionary algorithm was applied to back-analyze the permeability coefficient model parameters of the core material based on observation data of pore water pressure in the dam. Then, consolidation numerical analyses were performed by using the back-analyzed parameters and the constant permeability measured in situ, respectively. The spatial and temporal distribution of pore water pressure calculated by the back-analyzed parameters coincided quite well with the monitoring data during construction and operation. However, the numer...