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A comprehensive investigation, including experimental research, finite-element analysis, and theoretical derivation, was thoroughly carried out on the steel Q370 under strong corrosion to study its fracture mechanism further. Twenty-seven steel specimens were corroded by 36% industrial hydrochloric acid for 0, 1, 2, 4, 8, 12, 24, 48, and 72 h. In particular, a three-dimensional (3D) noncontact laser scanner measured the size of pits and roughness of the steel surface. To sum up, on the condition that the corrosion time has leaped, the section loss rate mushroomed nonlinearly. An inflection point in the curve of section loss rate occurs at 12 h, and then the growth in section loss rate keeps steady. Moreover, three-dimensional roughness parameters Sa , Sq , and Sp from 3D scanning have a linear increase, and both Ssk and Sv have a nonlinear increase; notwithstanding, Sku has a nonlinear reduction. This finding means growth of surface roughness in corroded specimens. Furthermore, considering the increase in the number of pits and the cross-section reduction, the specimen shows an obvious upward trend in fracture parameters. In this study, the cavitation growth and stress-modified critical strain models were modified to establish a strong corrosion fracture model of steel Q370, including von Mises stress, hydrostatic stress, equivalent plastic strain, and corrosion time. The fracture displacement errors with the comparison of test and finite-element values are within 7%, indicating that the fracture model can precisely simulate the fracture of steel Q370 after strong corrosion. This research can present a reference for the engineering application and subsequent investigation of steel Q370 that suffered strong corrosion. [ABSTRACT FROM AUTHOR]

The primary objective of this study was to investigate the constitutive relations and damage properties of concrete in complex stress states with different stress paths under high pressure. Monotonic hydrostatic pressure, cyclic hydrostatic pressure, uniaxial stress with lateral confinement, and multiaxial proportional stresses were applied in tests. High stresses reaching up to 500 MPa under the aforementioned four loading paths were achieved through a true triaxial testing system. A series of uniaxial tests were carried out after triaxial tests to evaluate the damage degree of concrete. Microscopic observations were also made to visualize the changes of microstructures of the specimen before and after the triaxial compressive tests. The most important finding of this study is that concrete suffers damage even before it is loaded to the ultimate strength under multiaxial compressive stress states, different from the commonly used concrete models that assume the concrete damage only occurs in the strain softening stage. This means the conventional deviatoric strength theory alone may not be sufficient to model concrete material damage under complex stress states, instead the combined effect of hydrostatic and deviatoric stress should be considered together in predicting the concrete material damage. This study also found cyclic hydrostatic loads could induce more severe damage to concrete than monotonic hydrostatic loads with the same stress amplitude. [ABSTRACT FROM AUTHOR]

In geothermal engineering, the long-term thermomechanical responses of sand and clay are difficult to predict due to the lack of an essential understanding of thermally induced volume change. Recent experimental studies have measured thermal creep of dry sand, glass beads, and clays. However, this universal phenomena of thermal creep has not been properly included in constitutive models of soils. In this paper, the Tsinghua ThermoSoil (TTS) model, previously developed for clay, is extended to describe thermal and mechanical creep of sand. The elemental thermal creep and thermal cyclic behavior of Todi clay and Bangkok sand, reported under hydrostatic stress or oedometric conditions, are reproduced by the proposed formulation. These comparisons show the following key features of behavior described by the extended model (e-TTS): (1) thermal creep of clay can produce either compressive or s1welling behavior depending on the consolidation stress history, (2) the heating rate and temperature range have significant influences on thermal creep, but only small effects on swelling behavior, (3) thermal cycling induces compression of sand, which is dependent on effective stress level and relative density, and (4) the e-TTS model predicts stabilization of thermal creep strains for sands over within 50–100 thermal cycles due to equalization of elastic and locked-in hysteretic strains. [ABSTRACT FROM AUTHOR]

An asphalt mixture is always in a complex stress state during the service life of pavement. Its resistance can be objectively characterized only by applying the strength theory to establish the failure criterion model in a three-dimensional stress state. Therefore, based on the double confining pressure triaxial test method, the failure characteristic test in complex stress state was carried out on AC-13 and AC-20 asphalt mixtures widely used in asphalt pavement in China. Meanwhile, according to the generalized octahedral theory, the experimental data of the failure characteristic point, and the strength characteristics of the asphalt mixture itself, the applicability of classical failure criteria, including Bresler-Pister, Ottosen, Willam-Warnke, Kotsovos, Podgorski, amended Zhao-Song, and twin-shear failure criteria was analyzed. In the aforementioned failure criteria models, the amended Zhao-Song failure criterion considered the difference in tension and compression of materials, the effect of hydrostatic stress, and the correlation of stress states of strength, which was consistent with the test results. Therefore, this model can be used as the resistance calculation model of asphalt mixtures in a complex stress state. [ABSTRACT FROM AUTHOR]

Clay minerals are platelike particles that play a critical role in problems involving swelling, deformation, and failure. Fundamental understanding of these phenomena and the parameters that influence them requires studies at the nanoscale. The nanoscale mechanism of the sliding of clay sheets at different states of hydration and hydrostatic stress was studied here using molecular dynamics in an isobaric–isothermal ensemble. The hydration state lay in the range of crystalline swelling (0–400 mgwater/gclay), and the hydrostatic pressure was varied in the range 5–12 GPa. Under hydrostatic pressures as high as several gigpascals, the mobility and the molecular structure of water are comparable to those of supercooled water. Despite high hydrostatic stresses, the failure was located in the shear-dominated zone. Examination of the molecular structure of interlayer water, number of hydrogen bonds, and their configuration during shear loading showed evidence of stick-slip phenomena similar to those found in thin films. The number of hydrogen bonds between interlayer water molecules increased as the clay–water system approached the slip point. Hydration state and hydrostatic stress influenced the stress–strain behavior of system and the average shear stress. The hydration states, in which the maximum average shear stresses occurred, coincided with the formation of the second, third, and fifth water layers. The shear strength decreased with the increase of water content above 340 mgwater/gclay. The nanoscale cohesion and friction angle of the layers were calculated using the Mohr–Coulomb failure criterion and were found to be in good agreement with previous studies. [ABSTRACT FROM AUTHOR]

The goal of this paper is to reveal the influence of temperatures on the triaxial strength of asphalt mixtures. The triaxial compression and triaxial tensile tests, as well as plane tensile and compression/axial tensile tests, which were developed by the self-developed triaxial test equipment to carry out the complex stress state under different temperatures (5°C, 10°C, 15°C, 20°C, and 25°C), were performed on the asphalt mixture. The ultimate failure strength of the material shows that the temperature and stress state significantly affect the triaxial strength characteristics of the asphalt mixture, and the three-dimensional strength decreases by the increase in temperature. Under the triaxial compression and triaxial tensile stress state, the resistance of the octahedral shear stress increases with the hydrostatic stress. A three-dimensional strength calculation model is established based on the influence of temperature and characterization by the tensile meridian, compression meridian, and failure strength envelope. It reveals the change of failure strength envelope with increasing temperatures and decreasing hydrostatic stress under complex stress state. It provides experimental and theoretical references to the design of asphalt pavement structure of different temperature conditions according to the three-dimensional stress state. [ABSTRACT FROM AUTHOR]

This work studied the coupled stretching and bending deformations of a through-thickness nonelliptical elastic inhomogeneity embedded in an infinite matrix within the context of Kirchhoff isotropic and laminated plate theory. The matrix was subjected to uniform remote membrane stress resultants and bending moments, and was also subjected to a concentrated rotational moment at any position. Our analysis, based on complex variable methods, indicated that when the nonelliptical shape of the inhomogeneity is suitably designed and when three specific conditions on the remote loading are met for a given set of material and geometric parameters characterizing the composite: (1) the elastic inhomogneity is harmonic, (2) the internal stress resultants inside the inhomogeneity are uniform and hydrostatic, and (3) the hoop membrane stress resultant and hoop bending moment on the matrix side are uniform along the inhomogeneity–matrix interface. A couple-loaded rigid harmonic inhomogeneity in the absence of remote loading and in the presence of a concentrated rotational moment at any position in the matrix was also obtained using a similar procedure. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) failure criteria based on the Hoek–Brown (HB) criterion and a general Lode dependence for rocks were proposed in this paper. The proposed failure criteria inherited the compression meridian from the HB criterion and can include independent shear meridians to construct the failure envelop surface. Four failure criteria [Rubin-Willam-Warnke (RWW), Rubin-Pan-Hudson, R1.65, and Rubin λ (R)] with curved-triangular cross sections and two failure criteria with hexagonal cross sections (Rubin-Mohr-Coulomb and Rubin-Hoek-Brown) were shown as examples of applications of the general Lode dependence to demonstrate its versatility. The material parameters involved in the new failure criteria can be easily obtained from conventional triaxial compression (TXC) tests. Polyaxial compression (PXC) test data for six different rocks at a variety of stress states from published literatures were used to validate the proposed failure criteria, in which the best-fitting parameters obtained from the TXC tests were used to predict the rock failure in PXC states of stress. The comparison results demonstrated that three criteria (RWW, R1.65, and R) with similar cross section shapes gave better predictions than the other three criteria. One 3D failure criterion (R1.65) with an empirical factor (λ = 1.65) to define the independent shear meridian was considered to be the best among them because the RWW criterion tended to underestimate the strength for some rocks and the R criterion involved an extra parameter λ, which needed to be fitted from expensive PXC tests. The use of best-fitting parameters obtained from TXC tests can provide satisfactory predictions for rock failure with σ2 dependence using the R1.65 criterion. [ABSTRACT FROM AUTHOR]

This article uses the relevance vector machine (RVM) for the prediction of the overconsolidation ratio (OCR) of fine-grained soils based on piezocone penetration test data. RVM provides an empirical Bayes method of function approximation by kernel basis expansion. It uses the corrected cone resistance (), vertical total stress (), hydrostatic pore pressure (), pore pressure at the cone tip (), and the pore pressure just above the cone base () as input parameters. An equation has also been developed for the determination of OCR. The developed RVM model gives the variance of the predicted data. Sensitivity analysis has been conducted for determining the influence of each input parameter. The results are also compared with some of the existing interpretation methods. Comparisons indicate that the developed RVM model performs better than the existing interpretation methods for predicting OCR. [ABSTRACT FROM AUTHOR]