A simple permanent deformation model of rockfill materials

Existing experimental results have shown that using a semi-log linear relationship between the permanent volumetric strain and cyclic number underestimates the volumetric deformation of rockfill materials with a large cyclic number, and that the error increases with the confining pressure. The existing permanent deformation models are not suitable for the seismic safety analysis of high dams during strong earthquakes. In this study, a series of large-scale triaxial cyclic loading tests of rockfill materials were performed, and a new permanent deformation model of rockfill materials was developed and validated with three kinds of rockfill materials. The results show that the proposed model can properly reflect the general features of the permanent deformation of rockfill materials. The main features of the model are as follows:(1) relations between the cyclic number and permanent volumetric/shear strain are described by hyperbolic functions, which can avoid underestimating the volumetric deformation occurring during strong earthquakes;(2) the model can capture the effect of the mean effective stress on the permanent volumetric strain, with greater confining pressure correlating to greater permanent volumetric deformation, and the permanent volumetric strain under low confining pressure near the dam crest can be well represented; and(3) the model can reflect the effect of the consolidation stress ratio on the permanent shear strain.

Influence of seismic wave type and incident direction on the dynamic response of tall concrete-faced rockfill dams

Owing to the stochastic behavior of earthquakes and complex crustal structure,wave type and incident direction are uncertain when seismic waves arrive at a structure.In addition,because of the different types of the structures and terrains,the traveling wave effects have different influences on the dynamic response of the structures.For the tall concrete-faced rockfill dam(CFRD),it is not only built in the complex terrain such as river valley,but also its height has reached 300 m level,which puts forward higher requirements for the seismic safety of the anti-seepage system mainly comprising concrete face slabs,especially the accurate location of the weak area in seism.Considering the limitations of the traditional uniform vibration analysis method,we implemented an efficient dynamic interaction analysis between a tall CFRD and its foundation using a non-uniform wave input method with a viscous-spring artificial boundary and equivalent nodal loads.This method was then applied to investigate the dynamic stress distribution on the concrete face slabs for different seismic wave types and incident directions.The results indicate that dam-foundation interactions behave differently at different wave incident angles,and that the traveling wave effect becomes more evident in valley topography.Seismic wave type and incident direction dramatically influenced stress in the face slab,and the extreme stress values and distribution law will vary under oblique wave incidence.The influence of the incident direction on slab stress was particularly apparent when SH-waves arrived from the left bank.Specifically,the extreme stress values in the face slab increased with an increasing incident angle.Interestingly,the locations of the extreme stress values changed mainly along the axis of the dam,and did not exhibit large changes in height.The seismic safety of CFRDs is therefore lower at higher incident angles from an anti-seepage perspective.Therefore,it is necessary to consider both the seismic wave type and incident direction during seismic capacity evaluations of tall CFRDs.

Clinical and neuroradiological features of 15 patients diagnosed with Marchiafava-Bignami disease

We retrospectively reviewed the clinical data of 15 patients with MBD who visited at The Affiliated Hospital of Jiujiang University and The Third Affiliated Hospital of Nanchang University between January 2014 and December 2018.The diagnosis of MBD was made based on the following criteria:(1) a history of chronic alcoholism or malnutrition;(2) acute or sub-acute onset of neuropsychiatric symptoms;(3) symmetrical hyperintensity of the CC on T2-weighted and FLAIR images;(4) exclusion of other diseases including Wernicke encephalopathy (WE),reversible splenial lesion syndrome,intra-cranial infections,cerebrovascular diseases,and demyelinating diseases of the central nervous system.Clinical data,including demographics (gender and onset age),risk factors,types of onset,clinical presentations,MRI findings,treatment and outcome,were collected.At the time of follow-up (time range:1-2 months),the treatment outcomes were classified as complete,partial,and bad according to the objective improvement in neurological findings during drug therapy (death,apathetic state,or vegetative state was considered as a bad outcome).

Reversible Cerebral Vasoconstriction Syndrome following Guillain-Barre Syndrome： A Rare Complication

To the Editor： Reversible cerebral vasoconstriction syndrome （RCVS） is well characterized by severe headaches, with or without other acute neurological symptoms, and diffuse segmental vasoconstriction of cerebral arteries, which resolves within 3 months. It has been reported predominantly in middle age, and the syndrome is more common in women than in men. Neuroradiological features of RCVS include convexity subarachnoid hemorrhage, intracerebral hemorrhage.