Response of jointed arches to earthquake excitation     

John F. Hall  Michael J. Dowling 《地震工程与结构动力学》1985,13(6):779-798

An efficient method for accurately modelling the gradual opening and closing of joints in two-dimensional slabs and arches has been devised. The method is used in computing the earthquake response of an arch which is a representative horizontal cross-section of a concrete arch dam. Responses of the arch with and without joints are compared to assess the effect of joint opening. An extension to three-dimensional arch dams is proposed.  相似文献   

The physical state of pore water of na smectite used as barrier component     

Roland Pusch  Torbjrn Carlsson 《Engineering Geology》1985,21(3-4):257-265

The molecules constituting the first hydrate layers on montmorillonite crystal platelets appear to be characterized by preferred orientation and, depending on the exchangeable cation, by an ice-like configuration. Such organized interlamellar water is concluded to contribute to the high swelling pressure and shear resistance, as well as to the very low hydraulic conductivity at high clay bulk densities. At low densities the parallel arrangement of the lamellae alters to edge-to-face associations and the fraction of free water increases. However, even at very low densities the homogeneity of the clay gel still offers very tortuous passages to flowing water, which is manifested by a very low hydraulic conductivity.  相似文献   

Creep in rock as a stochastic process     

Roland Pusch 《Engineering Geology》1984,20(4):301-310

The heterogeneous character of rock suggests the use of statistical mechanics for the formulation of models of plasticity and creep. A stochastic creep model which allows for large variations in strength and size of the involved rock mass is outlined. The model, which is analogous to a previously developed concept for clastic materials, is shown to account rather well for typical creep behaviour of rock at moderate stresses and temperatures. Thus, it yields the often observed linear relation between the creep strain and the logarithm of time.  相似文献   

Buried trees,water table fluctuations,and 3000 years of changing climate in west-central Oklahoma     

Stephen A. Hall  Christopher Lintz 《Quaternary Research》1984,22(1):129-133

A sequence of radiocarbon-dated buried trees, buried soils, a carbonate zone, and a molluscan fauna from Carnegie Canyon indicate that between 3200 and 2600 yr B.P. the climate of west-central Oklahoma was drier than today. A high water table accompanied a period of moister climate 2000 to 1000 yr B.P. The water table dropped after 1000 yr B.P. due to a change toward dry conditions.  相似文献   

An introduction to crystal optics. P. Gay, 1982 Longman,London and New York,ix + 262 pp., £6.95     

A. Hall 《Earth》1984,20(2):167-169

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Rock moisture content in the field and the laboratory and its relationship to mechanical weathering studies     

Kevin Hall 《地球表面变化过程与地形》1986,11(2):131-142

Rock moisture content is a major control of mechanical weathering, particularly freeze-thaw, and yet almost no data exist from field situations. This study presents moisture content values for rocks, taken from a variety of positions and conditions, in the maritime Antarctic. Additional information regarding the amount of water the rock could take up, as observed from laboratory experiments, is also presented. The results show that the approaches used in simulation experiments, particularly that of soaking a rock for 24 hours, may produce exaggerated results. It was found that the saturation coefficient (S-value) was a good indicator of frost susceptibility (based on water content) but that the derivation of that value may underestimate the potential of some rocks. The distribution of moisture within rocks is seen as an important, but unkown, factor. The results of these field moisture contents suggest that for simulations of freeze-thaw or hydration to be meaningful then they should have rock water contents based on field observations.  相似文献   

Vertical column abundances of HCN deduced from ground-based infrared solar spectra: Long-term trend and variability     

E. Mahieu  C. P. Rinsland  R. Zander  P. Demoulin  L. Delbouille  G. Roland 《Journal of Atmospheric Chemistry》1995,20(3):299-310

A set of high-resolution IR solar spectra recorded at the International Scientific Station of the Jungfraujoch, Switzerland, from 84/06 to 93/06, and at the National Solar Observatory McMath-Pierce solar telescope facility on Kitt Peak, Arizona, U.S.A. from 78/05 to 92/07 have been analyzed to determine the vertical column abundances of hydrogen cyanide, HCN, above the two stations. The analysis was based on least-squares curve fitting of calculated spectra to the observations encompassing the P4 and the P8 lines of HCN respectively located at 3299.5273 and 3287.2483 cm^–1. The results obtained for the two stations indicate that no significant long-term trend affects either of the two databases; however, this analysis reveals variable increases during springtime of up to a factor of 2 in the HCN total column above the Jungfraujoch and even up to 3 above Kitt Peak. The calculated mean vertical column abundances, excluding the spring observations, are equal to (2.55±0.30)×10¹⁵ molec./cm² (S.D.) and (2.75±0.30)×10¹⁵ molec./cm² respectively above the Jungfraujoch and the Kitt Peak observatories. Based on a realistic volume mixing ratio profile, these columns translate into mean volume mixing ratios equal to 190×10^–12 ppv at the respective altitudes of the stations.  相似文献   

Cyclotella-taxa (Bacillariophyceae) in lakes of the Alpine region and their relationship to environmental variables     

Sybille Wunsam  Roland Schmidt  Rolf Klee 《Aquatic Sciences - Research Across Boundaries》1995,57(4):360-386

Surface sediment diatom assemblages for 86 Alpine lakes were analysed focusing on the dominant genusCyclotella and corresponding environmental data. The range of morphological variability of theCyclotella bodanica/radiosa, C. distinguenda, C. ocellata, C. comensis andC. stelligera complexes was documented. Significance tests included in the canonical correspondence analysis (CCA) indicated that total phosphorus, conductivity and surface water temperature were significantly correlated withCyclotella taxa assemblage distribution. Numerical species optima and tolerances were calculated in respect to these significant variables using weighted averaging (WA) regression and calibration. CCA and WA were able to provide information about the environmental preferences of the various morphotypes observed.  相似文献   

The physical properties of quartz-micaschist and their application to freeze-thaw weathering studies in the maritime antarctic     

Kevin Hall 《地球表面变化过程与地形》1987,12(2):137-149

As part of a study on freeze-thaw weathering in the maritime Antarctic an investigation was made of the physical properties of the local rock. Tests were made of point-load compressive strength, Schmidt hammer in situ rock strength, moisture content, indentor resistance and the size range of weathering products. The resulting data were used to consider the form of freeze-thaw weathering operative in the field and its relationship to laboratory simulations. A distinct difference between ‘massive rock’ and ‘intact rock’ is observed in the field. It is suggested that future studies should generate a greater database pertaining to rock properties as it is an invaluable aid in the study of mechanical weathering.  相似文献   

A paleomagnetic study of the Bilecik Limestone (Jurassic), northwestern Anatolia     

I. Evans  S.A. Hall  M.F. Carman  M. Senalp  S. Coskun 《Earth and Planetary Science Letters》1982,61(1):199-208

Paleomagnetic analyses of samples collected from a 500 m thick Jurassic section in the Pontides reveal the presence of two components of remanent magnetization: an unstable, low-temperature component which is removed during thermal demagnetization through 220°C and a dominant component which displays consistent directions through 650°. Curie point and IRM studies indicate that goethite is responsible for the low-temperature component whereas both magnetite and hematite contribute to the more stable component. The pole position determined from the stable magnetization is located at 18.8°N, 91.8°E (α₉₅=7.7°, N=134) indicating that the section has undergone more than 90° clockwise rotation since the Late Jurassic. Ancillary geologic evidence, particularly the orientation of Jurassic facies belts is also consistent with a 90° clockwise rotation in this region of northwest Anatolia. The pole suggests that the section may also have migrated slightly northward. Although the age of these movements is currently unknow, it is proposed that they are principally related to the closure of the Neo-Tethys during the Late Cretaceous/Early Tertiary. Some of the rotation may be related to the right lateral movement along the North Anatolian Transform Fault which was initiated in the Miocene.  相似文献