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The present study extends the numerical manifold method to include the hydro‐mechanical model to investigate the effect of water flow in fractures on the stability of rock structures, particularly slopes. The proposed flow model is verified by a simple 2‐D flow problem in a homogeneous aquifer. Combining the water flow model with the earlier developed fracture evolution technique, the entire failure process of the rock slope due to a heavy rain is simulated. The results illustrate that the developed numerical manifold method can not only determine the trigger factor of the crack initiation but also model the failure processes related to crack initiation, propagation, block formation, detachment and sliding due to the water effect successfully. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
224.
C.S. Wong James R. Christian S.-K. Emmy Wong John Page Liusen Xie Sophia Johannessen 《Deep Sea Research Part I: Oceanographic Research Papers》2010,57(5):687-695
Partial pressure of CO2 (pCO2) in surface seawater has been measured in the northeastern Pacific Ocean at Station P and along Line P since 1973. These data have been divided into ‘oceanic’ and ‘coastal/transition’ zones, and the seasonal and interannual variability and the long-term trends for each zone have been examined. The oceanic zone shows little seasonality in surface seawater pCO2, with undersaturation throughout the year. A strong, biologically-driven seasonal cycle is offset by variation in temperature-dependent solubility of CO2. The coastal/transition zone shows a decline in pCO2 from winter–spring through summer and fall that is likely the result of seasonal stratification and convection rather than coastal upwelling. Interannual variability all along Line P is correlated with the multivariate ENSO index (MEI), with lower seawater pCO2 associated with El Niño conditions. Correlations with the Pacific Decadal Oscillation Index are similar but weaker, in part because there are few data prior to the 1976 regime shift. The long-term trend in seawater pCO2 in the oceanic zone is +1.36±0.16 μatm year?1, indistinguishable from the atmospheric growth rate, and varies little among the seasons. In the coastal/transition zone a slow increase in the pCO2 of surface seawater relative to that of the atmosphere has led to increasing undersaturation, particularly in spring. Aliasing of the seasonal and interannual variability due to sampling frequency may explain part of the observed trend in the coastal/transition zone, but real changes in physical or biological processes are also possible and require more detailed study. 相似文献
225.
Fracturing and Failure Behavior of Carrara Marble in Quasistatic and Dynamic Brazilian Disc Tests 总被引:1,自引:0,他引:1
Louis Ngai Yuen Wong Chunjiang Zou Yi Cheng 《Rock Mechanics and Rock Engineering》2014,47(4):1117-1133
The tensile strength and fracturing behavior of Carrara marble subjected to the dynamic Brazilian disc test using the split Hopkinson pressure bar technique are determined and compared with those obtained by the conventional quasistatic Brazilian disc test. Detailed observation of the cracking processes is aided by high-speed video footage captured at a frame rate of 100,000 frames per second. The dynamic increase factor is computed, revealing a strong strain rate dependence of the Carrara marble when subjected to strain rates above 1 s?1. Similar to the quasistatic loading tests, conspicuous white zones/patches commonly appear prior to the initiation of visible cracks in the dynamic loading tests. Identification of the white patch initiation and evolution is aided by image comparison software. Comparing the cracking and failure processes under quasistatic and dynamic loading, some distinct differences in the white patch geometry and initiation load are observed. In addition, the extent of the compressive failure zones around the contact points between the loading platens and specimens is found to increase with the strain rate. 相似文献
226.
Piles may be subjected to lateral soil pressures as a result of lateral soil movements from nearby construction‐related activities such as embankment construction or excavation operations. Three‐dimensional finite element analyses have been carried out to investigate the response of a single pile when subjected to lateral soil movements. The pile and the soil were modelled using 20‐node quadrilateral brick elements with reduced integration. For compatibility between the soil–pile interface elements, 27‐node quadrilateral brick elements with reduced integration were used to model the soil around the pile adjacent to the soil–pile interface. A Mohr–Coulomb elastic–plastic constitutive model with large‐strain mode was assumed for the soil. The analyses indicate that the behaviour of the pile was significantly influenced by the pile flexibility, the magnitude of soil movement, the pile head boundary conditions, the shape of the soil movement profile and the thickness of the moving soil mass. Reasonable agreement is found between some existing published solutions and those developed herein. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
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S. L. Breen S. P. Ellingsen M. Johnston-Hollitt S. Wotherspoon I. Bains M. G. Burton M. Cunningham N. Lo C. E. Senkbeil T. Wong 《Monthly notices of the Royal Astronomical Society》2007,377(2):491-506
We report the results of a blind search for 22-GHz water masers in two regions, covering approximately half a square degree, within the giant molecular cloud associated with RCW 106. The complete search of the two regions was carried out with the 26-m Mount Pleasant radio telescope and resulted in the detection of nine water masers, five of which are new detections. Australia Telescope Compact Array (ATCA) observations of these detections have allowed us to obtain positions with arcsecond accuracy, allowing meaningful comparison with infrared and molecular data for the region. We find that for the regions surveyed there are more water masers than either 6.7-GHz methanol, or main-line OH masers. The water masers are concentrated towards the central axis of the star formation region, in contrast to the 6.7-GHz methanol masers which tend to be located near the periphery. The colours of the GLIMPSE point sources associated with the water masers are similar to those of 6.7-GHz methanol masers, but slightly less red. We have made a statistical investigation of the properties of the 13 CO and 1.2-mm dust clumps with and without associated water masers. We find that the water masers are associated with the more massive, denser and brighter 13 CO and 1.2-mm dust clumps. We present statistical models that are able to predict those 13 CO and 1.2-mm dust clumps that are likely to have associated water masers, with a low misclassification rate. 相似文献
229.
Results from a three-dimensional ballistic model of Europa's O2 atmosphere are presented. Hubble Space Telescope (HST) ultraviolet observations show spatially non-uniform O2 airglow from Europa. One explanation for this is that the O2 atmosphere is spatially non-uniform. We show that non-uniform ejection of O2 alone cannot reproduce the required morphology, but that a non-uniform distribution of reactive species in Europa's porous regolith can result in a non-uniform O2 atmosphere. By allowing O2 molecules to react with Europa's visibly dark surface material, we produced a spatially non-uniform atmosphere which, assuming uniform electron excitation of O2 over the trailing hemisphere, compares favorably with the morphology suggested by the HST observations. This model, which requires a larger source of O2 than has previously been estimated, can in principal be tested by the New Horizons observations of Europa's O2 atmosphere. 相似文献
230.
Updated Galileo probe mass spectrometer measurements of carbon, oxygen, nitrogen, and sulfur on Jupiter 总被引:1,自引:0,他引:1
The in situ measurements of the Galileo Probe Mass Spectrometer (GPMS) were expected to constrain the abundances of the cloud-forming condensible volatile gases: H2O, H2S, and NH3. However, since the probe entry site (PES) was an unusually dry meteorological system—a 5-μm hotspot—the measured condensible volatile abundances did not follow the canonical condensation-limited vertical profiles of equilibrium cloud condensation models (ECCMs) such as Weidenschilling and Lewis (1973, Icarus 20, 465-476). Instead, the mixing ratios of H2S and NH3 increased with depth, finally reaching well-mixed equilibration levels at pressures far greater than the lifting condensation levels, whereas the mixing ratio of H2O in the deep well-mixed atmosphere could not be measured. The deep NH3 mixing ratio (with respect to H2) of (6.64±2.54)×10−4 from 8.9-11.7 bar GPMS data is consistent with the NH3 profile from probe-to-orbiter signal attenuation (Folkner et al., 1998, J. Geophys. Res. 103, 22847-22856), which had an equilibration level of about 8 bar. The GPMS deep atmosphere H2S mixing ratio of (8.9±2.1)×10−5 is the only measurement of Jupiter's sulfur abundance, with a PES equilibration level somewhere between 12 and 15.5 bar. The deepest water mixing ratio measurement is (4.9±1.6)×10−4 (corresponding to only about 30% of the solar abundance) at 17.6-20.9 bar, a value that is probably much smaller than Jupiter's bulk water abundance. The 15N/14N ratio in jovian NH3 was measured at (2.3±0.3)×10−3 and may provide the best estimate of the protosolar nitrogen isotopic ratio. The GPMS methane mixing ratio is (2.37±0.57)×10−3; although methane does not condense on Jupiter, we include its updated analysis in this report because like the condensible volatiles, it was presumably brought to Jupiter in icy planetesimals. Our detailed discussion of calibration and error analysis supplements previously reported GPMS measurements of condensible volatile mixing ratios (Niemann et al., 1998, J. Geophys. Res. 103, 22831-22846; Atreya et al., 1999, Planet. Space Sci. 47, 1243-1262; Atreya et al., 2003, Planet. Space Sci. 51, 105-112) and the nitrogen isotopic ratio (Owen et al., 2001b, Astrophys. J. Lett. 553, L77-L79). The approximately three times solar abundance of NH3 (along with CH4 and H2S) is consistent with enrichment of Jupiter's atmosphere by icy planetesimals formed at temperatures <40 K (Owen et al., 1999, Nature 402 (6759), 269-270), but would imply that H2O should be at least 3×solar as well. An alternate model, using clathrate hydrates to deliver the nitrogen component to Jupiter, predicts O/H?9×solar (Gautier et al., 2001, Astrophys. J. 550 (2), L227-L230). Finally we show that the measured condensible volatile vertical profiles in the PES are consistent with column-stretching or entraining downdraft scenarios only if the basic state (the pre-stretched column or the entrainment source region) is described by condensible volatile vertical profiles that are drier than those in the equilibrium cloud condensation models. This dryness is supported by numerous remote sensing results but seems to disagree with observations of widespread clouds on Jupiter at pressure levels predicted by equilibrium cloud condensation models for ammonia and H2S. 相似文献