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Sand-gravel mixtures are typical binary materials, exhibiting highly heterogeneous, discontinuous, and significant structural effects. The contact state between sand and gravel particles has a significant influence on the mechanical properties of the mixtures. This article focused on the complex internal structure and its mesostructural behavior of the mixtures, and a systematic statistical analysis was carried out to study the shape, size, and angularity of the coarse particles. The three-dimensional (3D) shapes of coarse aggregates were approximated to be hexahedron, pentahedron, and tetrahedron. An indicator called angularity and surface texture (AT) index was developed to characterize the combined effect of the coarse aggregate angularity and surface texture. Based on the screening testing and digital image processing, the particle size and AT index of aggregates were extracted, and their means, standard deviations, and statistical distributions were studied. An algorithm for generating 3D aggregates was developed based on the statistical results of the coarse aggregate 3D morphology. The coarse aggregate generating code was written using the fish language in PFC3D. The numerical model was then applied to conduct three typical monotonic or cyclic triaxial test simulations. Retrospective simulation of the laboratory tests using the proposed model showed good agreement, and the reliability of the model is effectively verified. The results interpreted well the mechanism of particle motion and the distribution of interparticle contact force during shearing from mesoscale of the mixtures, which can give better understanding and modeling of the nonlinear behavior of the sand-gravel mixtures.

The shear wave velocity (Vs)-based method of assessing the liquefaction susceptibility of soils has given geotechnical engineers a promising alternative for determining soil resistance to seismic liquefaction. Through the use of an expanded global case histories of soil liquefaction, the authors obtained a new calibrated correlation equation for liquefaction triggering analysis. This new liquefaction triggering correlation was found to be reasonably conservative, and yet insensitive to the variations in the components of the adopted simplified analysis framework. A probabilistic version of the liquefaction triggering correlation, obtained with the weighted maximum-likelihood technique, was validated using a weighted empirical probability approach. Three zones of liquefaction potential, transitioning from non-liquefaction to liquefaction, were then defined based on liquefaction probability contours.

Undrained cyclic loading patterns and consolidation states can significantly affect the deformation features of medium-dense saturated fine-grained sand. A series of undrained cyclic loading tests with different consolidation states, i.e., various mean effective consolidation stresses ( p 0 ), principal stress direction angles ( α 0 ), ratios ( R 0 ) of major and minor principal stresses, and relative magnitudes of intermediate principal stress ( b 0 ), were performed on saturated micaceous fine sand specimens with a relative density of 50% corresponding to a wide strain range in the order of 10 − 5 to 10 − 2 . The patterns of cyclic axial, torsional, and axial–torsional combined loadings were applied in a hollow cylinder apparatus. The small-strain shear modulus G 0 , the reference shear strain γ r , curves for shear modulus reduction G / G 0 , the damping ratio λ and Poisson's ratio υ with increasing strain were determined. The results of the cyclic axial–torsional combined tests showed a close relationship between G 0 , γ r , and υ as well as the consolidation state parameters p 0 , R 0 , α 0 , and b 0 . The G 0 and γ r increased nearly linearly with increasing p 0 and with decreasing α 0 or b 0 . The υ is strain dependent and increases as the p 0 decreases. Tests indicated that the reduction of G with increasing shear strain γ became more pronounced as p 0 increased. The relationship for the G / G 0 versus γ / γ r was approximately independent of the cyclic loading patterns and the various values of parameters p 0 , R 0 , α 0 , and b 0 . A slight difference is noted between the damping ratios λ t and λ z , corresponding to vertical and torsional deformations. An empirical model was proposed for the dependence of the increase in damping ratio characteristics on the deviatoric strain.

The post-earthquake rapid risk evaluation on the reservoir dams plays an important role in the emergency danger disposal and reinforcement. The fuzzy Data Envelopment Analysis/Assurance Region (DEA/AR) approach was introduced evaluating the seismic behavior of reservoir dams, in which the seismic risk of dam site, the structure characteristics of reservoir dam, and pre-earthquake state of dams were taken as input variables; in the meantime the seismic crack, leakage and deformation of dams induced by the earthquake were taken as output variables. The proposed DEA/AR approach was adopted to evaluate the seismic behavior of 19 reservoir dams suffered from Wenchuan earthquake in Luojiang County, Sichuan Province. The input and output variable values all originated from the post-earthquake field investigation data. And the weight values of DEA/AR model were determined by the entropy weight method which was able to avoid the interference from subjective consciousness. The evaluation results on the seismic behavior obtained from DEA/AR approach were mainly consistent with those from the experts in the field, which verified that the approach was valid and rational. The proposed DEA/AR approach was based on the objective data and the cognitive ability of the model self to give the evaluation results, which was adaptive for the situation that the seismic behaviors of the reservoir dams were not easy to distinguish. A ranking method was recommended to judge the order of quality of seismic behavior of the evaluated reservoir dams. The ranking results could serve for the post-earthquake emergency disposal and reinforcement.

The XUV spectra emitted from line focused laser-produced Ge plasma were observed. A 1-m grazing-incidence spectrograph viewed the plasma in the axial direction. The spectra due to transitions in GeXX-GeXXVI were identified. The wavelengths and intensities were obtained. Calculations on spontaneous decay rates and oscillator strengths of the spectra were performed.