On hardening anisotropy of K0-consolidated clays

The combined isotropic-kinematic hardening rule for clays is presented using the concept of a multisurface model discussed previously in Reference 1. The mechanical behaviour of clays after one-dimensional consolidation is next simulated for the axisymmetric stress stress state. A general three-dimensional formulation of constitutive relations is also presented.     

Design charts for a deep circular tunnel under non-uniform loading

Summary This paper describes design charts which can be used to quickly predict the size and shape of the failed rock regions caused by the excavation of a deep tunnel, and the induced closure for cases of non-uniformin-situ stress fields. Through a simple graphical construction, the design charts can also be used to evaluate the performance of a support system.Previously of J. F. T. Agapito and Associates, U.S.A.     

Statistical analysis of seismic faulting

Summary A calculation of the slip angle and an analysis of the type of faulting associated with earthquakes was made from the presently available fault-plane solutions in the same fashion as this was done six years ago for the then available fault plane solutions. Most of the earlier results were confirmed: It was found that there exist certain large scale areas in the world which can now be much more specifically defined than previously, with a predominance of either strike-slip or dip-slip faulting. There is no evidence of a level of no strain from seismic data since there is no indication of a distinct decrease of pressure type faulting with increasing depth.     

High-resolution microwave spectra of solar bursts

Microwave observations with exceptionally high spectral resolution are described for a set of 49 solar flares observed between May and October 1981. Total power data were obtained at 40 frequencies between 1 and 18 GHz by the Owens Valley frequency-agile interferometer with 10 s time resolution. Statistical analysis of this sample of microwave bursts established the following significant characteristics of their microwave spectra: (i) Most ( 80%) of the microwave events displayed complex spectra consisting of more than one component during some or all of their lifetime. Single spectral component bursts are rare. It is shown that the presence of more than one component can lead to significant errors when data with low spectral resolution are used to determine the low-side spectral index. (ii) The high-resolution data show that many bursts have a low-side spectral index that is larger than the maximum value of about 3 that might be expected from theory. Possible explanations include the effect of the underlying active region on the perceived burst spectrum and/or the necessity for more accurate calculations for bursts with low effective temperatures, (iii) the peak frequencies of the bursts are remarkably constant during their lifetimes. This is contrary to expectations based on simple models in which the source size and ambient field remain constant during the evolution of a burst.Swiss National Science Foundation Fellow from the University of Bern.     

Interpretation of spectra of geomagnetic pulsations as a spectrum of modulated oscillations

Summary The analysis of spectra of modulated oscillations is used to show how these oscillations are distorted when recorded by an instrument whose characteristics depend on frequency, and under what conditions the parameters of the original modulated oscillations can be derived directly from the record. Geomagnetic Pc3 and Pi2 pulsations, recorded at the Budkov Observatory, are discussed; these can be interpreted as amplitude or frequency modulated oscillations.

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Phyllosilicates in the matrix of the unique carbonaceous chondrite Lewis Cliff 85332 and possible implications for the aqueous alteration of CI chondrites

Abstract— The fine-grained matrix of the unique, unequilibrated carbonaceous chondrite Lewis Cliff (LEW) 85332 has been studied by scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). Compositionally, LEW 85332 has a matrix that is more Fe-rich than typical CI chondrites but has elemental abundance ratios that appear to be closer to CI matrices than to CM or CR chondrites. The mineralogy of the matrix is dominated by phyllosilicate phases that are predominantly interlayered Fe-rich serpentine/saponite; anhydrous silicate phases such as olivine and pyroxene are rare. Minor magnetite, troilite and ferrihydrite also occur associated with the phyllosilicates. Despite the high degree of weathering in LEW 85332, the phyllosilicates appear to have an extraterrestrial origin, but the highly variable Mg/Fe ratios of saponite may be the result of partial terrestrial oxidation of Fe-rich saponite to a more Mg-rich saponite and ferrihydrite. Alternatively, some of the ferrihydrite may have formed as a result of terrestrial weathering of Fe-Ni metal. The compositional and mineralogical data suggest that the matrix of LEW 85332 may represent a very early stage in the type of aqueous alteration experienced by the CI chondrites, although it is improbable that LEW 85332 was a precursor to the CI chondrites because of its high abundance of chondrules. The absence of carbonates, the high-Fe content of the matrix and phyllosilicate phases and relatively low abundance of magnetite all indicate that the degree of oxidation and leaching of LEW 85332 matrix was significantly less than that experienced by the CI chondrites. The absence of clear evidence for alteration of chondrules suggests that either the formation of the hydrous phases in the matrix occurred prior to accretion or that alteration occurred on a parent body and involved limited amounts of fluid, such that the reactions took place preferentially and exclusively within the fine-grained (anhydrous?) matrix materials.     

The role of trace elements in controlling H incorporation in San Carlos olivine

We conducted a series of hydroxylation experiments using mm-sized cuboids cut from six different crystals of San Carlos olivine with a range of trace-element concentrations. The cuboids were pre-annealed and then hydroxylated under identical conditions, ensuring that variation in the amounts of H incorporated depended only on the compositional variables. The pre-anneal was at 1400 °C, atmospheric pressure and an oxygen fugacity equivalent to Δlog FMQ?+?1, with the subsequent hydroxylation at 800 °C and 1.5 GPa, for 3 days. Hydrogen was incorporated into all six crystals by the four main substitution mechanisms [Si], [Mg], [Ti] and [triv], with homogeneous H contents in the cores of the crystals, indicating H diffusion rates faster than 10^??11 m²/s. Total H as H₂O in the homogeneous cores calculated by summing all the infrared absorbance bands ranges from 13 to 27 wt. ppm. The total H₂O in the six pre-annealed crystals is poorly correlated with any measured compositional variable. However, when the H₂O associated with individual infrared bands is compared, clear trends emerge. The intensity of absorption bands at 3572 and 3525 cm^??1 are strongly correlated with Ti concentrations, whose range in the six crystals exceeds an order of magnitude. Bands between 3400 and 3300 cm^??1, correlate negatively with Na⁺, but are positively correlated with the difference between molar Cr³⁺ and Na⁺. This highlights a previously unrecognised role for Na in suppressing H incorporation in natural olivines. The results confirm the important role that the trace constituents of olivine play in H incorporation. Two of these trace elements, Na and Ti, tend to be similarly enriched or depleted by partial melting or metasomatism of the mantle, but have opposite effects on H incorporation, with Ti enhancing it but Na suppressing it. Models estimating the effect of H in olivine on mantle rheology must, therefore, consider carefully the availability of these trace elements.     

Fractured bedrock and saprolite hydrogeologic controls on groundwater/surface-water interaction: a conceptual model (Australia)

Hydrologic conceptual models of groundwater/surface-water interaction in a saprolite-fractured bedrock geological setting often assume that the saprolite zone is hydraulically more active than the deeper bedrock system and ignore the contribution of deeper groundwater from the fractured bedrock aquifer. A hydraulic, hydrochemical, and tracer-based study was conducted at Scott Creek, Mount Lofty Ranges, South Australia, to explore the importance of both the deeper fractured bedrock aquifer system and the shallow saprolite layer on groundwater/surface-water interaction. The results of this study suggest that groundwater flow in the deeper fractured bedrock zone is highly dynamic and is an important groundwater flow pathway along the hillslope. Deep groundwater is therefore a contributing component in streamflow generation at Scott Creek. The findings of this study suggest that hydrologic conceptual models, which treat the saprolite-fractured bedrock interface as a no-flow boundary and do not consider the deeper fractured bedrock in hydrologic analyses, may be overly simplistic and inherently misleading in some groundwater/surface-water interaction analyses. The results emphasise the need to understand the relative importance of subsurface flow activity in both of these shallow saprolite and deeper bedrock compartments as a basis for developing reliable conceptual hydrologic models of these systems.