Passive Side Research Articles

Bedded barite deposits in the United States, Canada, Germany, and China; two major types based on tectonic setting

Bedded barite deposits can be divided into two types based on stratigraphic succession, tectonic setting, and geochemistry. The first, herein termed the margin has abundant chert in the host sediments, is deposited in small ocean basins lying between a subduction zone and a passive continental margin, and has a geochemical signature that suggests an appreciable influence of oceanic crust. The barite is deposited on or adjacent to the passive margin side of the basin. Subduction leads to consumption of the ocean floor of the basin, collision of the volcanic arc with the passive margin, and thrusting of the barite-bearing sedimentary sequence onto the stable platform. This group of deposits lacks economic accumulations of Pb and Zn. Examples are the Fancy Hill and Chamberlain Creek deposits in the Ouachita Mountains of Arkansas and the East Northumberland Canyon deposit in central Nevada. The second type, for which we propose the term rift is hosted by coarse clastics of turbidity current origin and is deposited in intracratonic rifts with strong local relief; the host rocks have a chemistry suggesting entirely continental affinities. Volcanic rocks, where present, tend to be alkalic basalts. Most barite deposits of this type are accompanied by economic accumulations of Pb and Zn. Examples include the Meggen and Rammelsberg deposits in Germany and the Anvil and Howard's Pass deposits in the Selwyn basin of western Canada.The barite deposits of south China can be assigned tentatively to these two types. Those of the Qinling district were deposited in a chert-dominated section on oceanic crust in a closing, remnant-ocean basin, placing them in the continental margin type. Those of the Jiangnan region are chemically more like the cratonic rift-type deposits and seem to reflect a similar tectonic setting. If this assignment is correct, the Jiangnan area should be considered prospective for Pb and Zn mineralization near the barite deposits.

The hydrogen permeation through passivating film on iron by modulation method

The permeation of hydrogen through the passivating oxide film on iron has been studied by a modulation method as a function of cathodic charging potential, anodic passivation potential and temperature. The diffusivity of hydrogen in the oxide film is determined from the measured phase shift between the input hydrogen concentration and the hydrogen flux at the passivated side of the specimen. The diffusivity of hydrogen in the oxide is found to increase with increasing hydrogen content in the oxide produced either by increasing the input concentration of hydrogen or by decreasing the passivating potential. The electric field across the oxide, and the potential drop and the hydrogen concentration ratio across the metal-oxide interface are evaluated. The concentration ratio is explained in terms of the interfacial potential drop and the ratio of activity coefficients of hydrogen in the two phases.

Mechanics and performance of a tied‐back wall under seismic loads

AbstractIn this paper the stability of a tied‐back wall subjected to seismic loads is analysed for a predetermined mode of failure (rotation about the top of the wall) and the analysis is compared with data from tests on this type of wall using the seismic simulator at the State University of New York at Buffalo. We carried out a pseudo‐static analysis of the problem using the Mononobe‐Okabe earth pressure coefficients, wherein the dynamic effects due to the seismic loading are converted into equivalent static loads. The acceleration ratio at which the wall fails by rotation about the top was obtained by considering the moments due to the various lateral earth pressure resultants and the inertial forces induced in the soil due to the seismic loading.We found that the presence of wall friction on the passive side significantly enhances the stability of the flexible retaining wall under seismic loads. Thus, flexible retaining walls supporting dry cohesionless soil can be very efficient during earthquakes. Under moderate earthquakes, an increase in the depth of embedment increases the dynamic factor of safety significantly. However, beyond a certain acceleration ratio for a soil with a particular value of ø, any increase in the depth of emdedment has no effect in impeding failure, irrespective of any change in the geometry of the system. Seismic design charts are presented to evaluate the stability of, and to design, flexible retaining walls embedded in dry cohesionless soils under seismic loading.

Finite element analysis of a centrifuge model of a retaining wall embedded in a heavily overconsolidated clay

The current study is aimed at the behaviour right upto collapse of a retaining wall embedded in overconsolidated clay. It is found that the excess pore pressures generated due to the excavation are fairly well simulated. The rupture lines on the passive side in the centrifuge model test were closely matched by two lines along which the stress state was reaching the critical state in the analysis. The displacements on the active side were not well matched especially the vertical settlements near to the wall. The bending moments were significantly overpredicted. The prop force due to excavation was also overpredicted. This is to be expected because the prop was modelled as rigid in the analysis.

Clay Anisotropy and Braced Wall Behavior

A technique is presented which modifies the basal heave analysis procedures for braced excavations to account for the strength anisotropy exhibited by most natural, soft to medium clays. In the case of a braced wall, the clay on the passive side of the wall can develop a much lower strength than the clay on the active side, if the clay is strongly anisotropic. Since the existence of a lower strength zone is not considered by conventional basal heave analysis procedures, these techniques theoretically lead to an overestimate of basal stability. Finite element analyses are used to demonstrate the effects of anisotropy on the behavior of braced excavations. Analysis results show that if the soil is presumed to be isotropic when it is truly anisotropic the following trends develop: (1) The basal heave safety factor may be from 10 to 50 percent larger than the actual one, depending on the degree of anisotropy; (2) lateral wall movements and ground surface settlements can be larger than expected; and (3) unusually high loads can develop on the lower struts in cases of marginal stability.

Montesquieu and Penal Law Reform in England

In Montesquieu's philosophy, laws in general are necessary relationships inherent in the very nature of things. Civil laws may therefore be said to have a double function: on the passive side, they define “natural” relationships between different people and things; on the active side, they aim at reknitting “natural” relationships that have been dissolved. It is in this latter function that they may become penal.