The critical state and steady state of sand: A literature review

Abstract

The critical state and steady state theories are widely accepted for simulating the soil behavior and providing a basis for liquefaction evaluation and constitutive modeling. However, there was conflicting evidence regarding the critical state and steady state of sands in the last decades. In some cases, the critical state and steady state are taken to be identical and in others they differ significantly. Whether they are the same or not remain a hot academic debate to date. This paper provides a critical review on the origin and history of the critical state and steady state of sands, which identifies conflicting evidences and discusses the influencing factors on the existence and uniqueness of critical state and steady state. Based on a critical review of literature, it is concluded that the steady state concept is a refinement of the critical state concept and the uniqueness of the critical state and steady state was affirmed. Special care should be paid in the laboratory techniques in order to accurately measure the critical state and steady state due to the numerous influencing factors of them.     

Periodicities in blue crab population of Chesapeake Bay

Analysis of the annual blue crab catch in Chesapeake Bay for the years 1922–1976 shows that there are variations with periods of 18.0, 10.7, and 8.6 years. Analysis of Philadelphia air temperatures shows periods of 17.5, 9.8, and 7.4 years. The periods of 18.0 and 17.5 years agree with the 18.6 year period of the Earth-Moon-Sun tidal force, and the periods of 8.6 and 7.4 years agree with the 8.8 year period of the Earth-Moon-Sun tidal force, within experimental error. The periods of 9.8 and 10.7 years, for the temperatures and crabs, respectively, are probably related to the 10.5 year sunspot cycle within experimental error.     

Mantle convection with a brittle lithosphere: thoughts on the global tectonic styles of the Earth and Venus

Plates are an integral part of the convection system in the fluid mantle, but plate boundaries are the product of brittle faulting and plate motions are strongly influenced by the existence of such faults. The conditions for plate tectonics are studied by considering brittle behaviour, using Byerlee's law to limit the maximum stress in the lithosphere, in a mantle convection model with temperature-dependent viscosity.
When the yield stress is high, convection is confined below a thick, stagnant lithosphere. At low yield stress, brittle deformation mobilizes the lithosphere which becomes a part of the overall circulation; surface deformation occurs in localized regions close to upwellings and downwellings in the system. At intermediate levels of the yield stress, there is a cycling between these two states: thick lithosphere episodically mobilizes and collapses into the interior before reforming.
The mobile-lid regime resembles convection of a fluid with temperature-dependent viscosity and the boundary-layer scalings are found to be analogous. This regime has a well defined Nusselt number–Rayleigh number relationship which is in good agreement with scaling theory. The surface velocity is nearly independent of the yield stress, indicating that the 'plate' motion is resisted by viscous stresses in the mantle.
Analysis suggests that mobilization of the Earth's lithosphere can occur if the friction coefficient in the lithosphere is less than 0.03–0.13—lower than laboratory values but consistent with seismic field studies. On Venus, the friction coefficient may be high as a result of the dry conditions, and brittle mobilization of the lithosphere would then be episodic and catastrophic.     

Lizards and snakes from the late Miocene hominoid locality of Ravin de la Pluie (Axios Valley,Greece)

We here describe lizards and snakes from the late Miocene (MN 10) of Ravin de la Pluie, near Thessaloniki, Greece, a locality widely known for its hominoid primate Ouranopithecus macedoniensis. The new finds comprise two large-sized lizards (a probable anguine and a varanid) and two snakes (an elapid and a small-sized “colubrine”). Even if the material is represented by few specimens, this is the first record of squamates from the late Miocene MN 10 biozone of southeastern Europe and the third only for the whole continent. The importance of the varanid vertebrae for systematic attributions is discussed. The new varanid limb elements described herein rank among the few such specimens in the fossil record of monitor lizards. Judging from the new and previously published varanid appendicular material, we suggest that Neogene monitor lizards from Europe possessed comparatively short and robustly built limbs. Distinctive scars on one of the limb elements are interpreted as bite marks of a predator or scavenger, offering insights on the palaeoecology of the herpetofauna of the locality.     

Residues of environmental pollutants and necropsy data for Eastern United States ospreys, 1964–1973

Thirty-three ospreys (Pandion haliaetus) that were found dead or moribund in the Eastern United States between 1964 and 1973 were necropsied. The brains and carcasses of 26 of these birds were analyzed for organochlorines. The livers of 18 and the kidneys of 7 were analyzed for selected metals. Most adults were recovered in April and May and most immatures were recovered in August through October. The adult sex ratio was highly unbalanced in favor of females. Major causes of mortality were impact injuries, emaciation, shooting, and respiratory infections. Of special interest were two birds with malignant tumors and one with steatitis. Many birds had undergone marked weight losses resulting in mobilization and redistribution of organochlorine residues. Organochlorines were detected in the birds at the following percentages: DDE 100%, PCB 96%, DDD 92%, dieldrin 88%, chlordanes (including nonachlors) 82%, DDT 65%, and heptachlor expoxide 38%. Organochlorine levels tended to be higher in adults than in immatures. One adult from South Carolina had a potentially dangerous level of dieldrin in its brain, which might have contributed to its death. Immature ospreys from Maryland had extremely elevated levels of copper in their livers compared with immatures from other areas and all adults. One immature from Maryland had an elevated level of arsenic in its liver, which might have contributed to its death. One adult from Florida that had died of impact injuries had potentially dangerous levels of mercury in both liver and kidney and slightly elevated levels of cadmium in these tissues. Additional birds appeared to have been exposed to contamination of the environment by arsenic and mercury. The levels of chromium, zinc, and lead in livers appeared normal.     

Organic geochemistry of DSDP Site 467, offshore California,Middle Miocene to Lower Pliocene strata

Results of the analyses of twenty-three samples from the Middle Miocene to Lower Pliocene strata from DSDP Site 467, offshore California, are presented. The analyses were performed with the aim of determining the origin of the organic matter, the stratigraphic section's hydrocarbon generation potential and extent of organic diagenesis. Organic carbon contents are an order of magnitude greater than those typically found in deep sea sediments, suggesting an anoxic depositional environment and elevated levels of primary productivity. Hydrocarbon generation potentials are above average for most samples. The results of elemental analyses indicate that the kerogens are primarily composed of type II organic matter and are thermally immature. Analysis of the bitumen fractions confirms that the samples are immature. In cores from 541 to 614 meters, the gas chromatograms of the C₁₅₊ non-aromatic hydrocarbon fractions are dominated by a single peak which was identified as 17α(H), 18α(H), 21β(H)-28, 30-bisnorhopane. This interval is the same area in which the highest degrees of anoxia are observed as reflected by the lowest pristane/phytane ratios. This correlation may have some implications with regard to the origin of the bisnorhopane and its possible use as an indicator of anoxic depositional conditions within thermally immature sediments.