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1.
Zhou  Haizuo  Zheng  Gang  Liu  Jifu  Yu  Xiaoxuan  Yang  Xinyu  Zhang  Tianqi 《Acta Geotechnica》2019,14(5):1571-1584

Rigid columns penetrating a firm underlying stratum have often been used to enhance the stability and improve the settlement of embankments over soft ground. Furthermore, an inclined underlying stratum is commonly encountered in engineering practice. This investigation experimentally and numerically studies the performance of embankments over soft ground reinforced by rigid columns with various embedment depths. In centrifuge tests, a tilting failure occurs for columns with an embedment depth Le of 2D (D is the diameter of columns), whereas the embankments remain stable for Le of 7D. This result indicates that the inclined underlying stratum weakens the restraint effect at the column base and that a greater embedment depth is required to ensure the stability of embankments. Parametric studies numerically reveal that there exists a critical embedment depth, which represents a shift in the failure mechanism. The optimum column layout is determined based on the contributions of columns in different locations beneath an embankment. Finally, the influence of the embedment depth on the distribution of the bending moment of the columns and the soil reaction are discussed.

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2.
Earthquakes in Switzerland and surrounding regions during 2004   总被引：1，自引：0，他引：1  
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2004. During this period, 677 earthquakes and 96 quarry blasts were detected and located in the region under consideration. With 22 events with ML≥2.5, the seismic activity in the year 2004 was close to the average over the last 30 years. As in previous years, most of the activity was concentrated in the Valais and in Graubünden. In addition, several moderate earthquakes occurred in the lower crust below the northern Alpine foreland. Unusual was that five earthquakes were sufficiently strong to cause ground shaking of intensity IV over large portions of the territory. Two were located in Switzerland (Liestal, ML 3.8, and Brugg, ML 4.0). The epicenters of the other three strong events were located outside Switzerland (Besan?on in the French Jura, ML 4.8, Waldkirch in southern Germany, ML 5.1, and Lago di Garda in northern Italy, ML 5.3).  相似文献   

3.
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2008. During this period, 451 earthquakes and 75 quarry blasts were detected and located in the region under consideration. The three strongest events occurred in the Valais, near Lac des Toules (ML 3.6), and in Graubünden, near Ilanz (ML 3.7) and Paspels (ML 4.0). Although felt by the population, they were not reported to have caused any damage. However, with a total of only 15 events with ML ≥ 2.5, the seismic activity in the year 2008 was far below the average over the previous 33 years.  相似文献   

4.
The Fe L 2,3-edge spectra for a range of natural minerals and synthetic solid solutions have been measured using the technique of parallel electron energy-loss spectroscopy (PEELS) recorded in a transmission electron microscope (TEM). The Fe L 2,3 -edges of the minerals are characterised by two white-line features and exhibit electron energy-loss near-edge structure (ELNES) characteristic of Fe valence state. For divalent iron, the Fe L 3 -edge spectra are dominated by a sharp peak (white-line) at ca. 707.8 eV, followed by a broader and less intense peak at ca. 710.5 eV. The ELNES on the Fe L 3 -edge of trivalent iron consists of a white-line with its maximum at ca. 709.5 eV and a preceeding peak at ca. 708.0 eV. Mineral solid solutions that contain both Fe2+ and Fe3+ exhibit an Fe L 3 -edge shape that is composed of Fe L 3 -edges from the respective Fe2+- and Fe3+-bearing end members. The integral Fe L 2,3 -edge white-line intensity ratios I(L 3 )/I(L 2 ) show clear differences for Fe2+ and Fe3+. We demonstrate the feasibility of quantification of the ferrous/ferric ratio in minerals by determining the integral Fe L 2,3 -edge white-line intensity ratios I(L 3 )/I(L 2 ) as a function of the ferric iron concentration resulting in an universal curve within the experimental errors. The application of the universal curve combined with the high spatial resolution using the PEELS/TEM allows the quantification of the ferric iron concentration on a scale down to 10 nm, which is illustrated from a sample of ilmenite containing hematite exsolution lamellae that shows different Fe L 2,3 -edge shapes consistent with variations in the Fe2+-Fe3+ ratio over distances of ca. 100 nm. Received: 30 July 1997 / Revised, accepted: 26 October 1997  相似文献   

5.
The patterns of deformed early lineations (L1) over later folds (F2) can be classified into several morphological types depending on the nature of variation of L1 F2 over the folds. The field relations indicate that the folds under consideration are neither shear folds nor parallel folds modified by flattening. The lineation patterns are therefore interpreted in terms of an empirical model of simultaneous buckling and flattening in which it is assumed that (i) the central surface of the folded layer remains a sine curve in transverse profile, (ii) the ratio of rates of buckle shortening to homogeneous strain is proportional to sin 2a, with a as the dip angle and (iii) the progressive deformation is coaxial with the Z-axis of bulk strain parallel to the planar segments of the early folds. The model gives an insight into the relative importance of different physical factors which control the development of dissimilar lineation patterns. Not all lineation patterns are explicable by this simplified model. Thus complex patterns with variable L1 F2 along the fold axis may develop by a progressive rotation of the geometrically defined fold hinge through successive material lines. The theoretical results have been applied to interpret the lineation patterns in Central Rajasthan, India. It is concluded that L1 was initially very close to the E-ESE trending subhorizontal Z-axis of bulk deformation during F2-folding and that the X-axis was subhorizontal or gently plunging with a N-NNE trend.  相似文献   

6.
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7.
A data set of three-component short-period digital seismograms recorded in Friuli after the strong earthquake of 6th May 1976, allowed the local magnitude ML and the seismic moment M0 to be estimated in the range 0 < ML < 2. The data set including the same parameters for the higher-magnitude Friuli events (ML 5) shows two different slopes for the relation Log M0 = CML + d for the two different ranges of ML. One finds C ~ 1.0 (for 0 < ML < 2) and C ~1.5 (for5 ML 6.2), respectively.This implies that apparent stress release increases at low magnitudes, while it appears to be comparatively independent of the magnitude and to have an average value of about 100 bar for higher-magnitude earthquakes. Conversely, the fault dimensions do not appear to be magnitude-dependent for ML < 2; for higher-magnitude events the linear fault dimensions range from about 1 km at ML ~ 5 to about 12 km for the strong earthquake of 6th May 1976 (ML = 6.2).  相似文献   

8.
In this paper, liquefaction potential of soil is evaluated within a probabilistic framework based on the post-liquefaction cone penetration test (CPT) data using an evolutionary artificial intelligence technique, multi-gene genetic programming (MGGP). Based on the developed limit state function using MGGP, a relationship is given between probability of liquefaction (PL) and factor of safety against liquefaction using Bayesian theory. This Bayesian mapping function is further used to develop a PL-based design chart for evaluation of liquefaction potential of soil. Using an independent database of 200 cases, the efficacy of the present MGGP-based probabilistic method is compared with that of the available probabilistic methods based on artificial neural network (ANN) and statistical methods. The proposed method is found to be more efficient in terms of rate of successful prediction of liquefaction and non-liquefaction cases, in three different ranges of PL values compared to ANN and statistical methods.  相似文献   

9.
The structural evolution of tectonically deformed coals（TDC） with different deformational mechanisms and different deformational intensities are investigated in depth through X-ray diffraction（XRD） analysis on 31 samples of different metamorphic grades(Ro,max:0.7%-3.1%) collected from the Huaibei coalfield.The results indicated that there are different evolution characteristics between the ductile and brittle deformational coals with increasing of metamorphism and deformation.On the one hand,with the increase of metamorphism,the atomic plane spacing (d002) is decreasing at step velocity,the stacking of the BSU layer（Lc） is increasing at first and then decreasing,but the extension of the BSU layer（La） and the ratio of La/Lc are decreasing initially and then increasing.On the other hand,for the brittle deformational coal,d002 is increasing initially and then decreasing,which causes an inversion of the variation of Lc and La under the lower-middle or higher-middle metamorphism grade when the deformational intensity was increasing.In contrast,in the ductile deformational coals,d002 decreased initially and then increased,and the value of Lc decreased with the increase of deformational intensity.But the value of La increased under the lower-middle metamorphism grade and increased at first and then decreased under the higher-middle metamorphism grade.We conclude that the degradation and polycondensation of TDC macromolecular structure can be obviously impacted during the ductile deformational process,because the increase and accumulation of unit dislocation perhaps transforms the stress into strain energy.Meanwhile,the brittle deformation can transform the stress into frictional heat energy,and promote the metamorphism and degradation as well.It can be concluded that deformation is more important than metamorphism to the differential evolution of the ductile and brittle deformational coals.  相似文献   

10.
This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2006. During this period, 572 earthquakes and 91 quarry blasts were detected and located in the region under consideration. Of these earthquakes, two occurred in conjunction with the construction of the new Gotthard railway tunnel and 165 were induced artificially by the stimulation of a proposed geothermal reservoir beneath the city of Basel. With 20 events with M L ≥ 2.5, five of which were artificially induced, the seismic activity in the year 2006 was far below the average over the previous 31 years. Nevertheless, six events were felt by the public, most prominently the strongest of the induced Basel events (M L 3.4), which caused some non-structural building damage. Noteworthy are also the two earthquakes near Cortaillod (M L 3.2), on the shore of Lake Neuchatel, and in Val Mora (M L 3.5), between the Engadin and Val Müstair, as well as the 42 aftershocks of the M L 4.9 Vallorcine earthquake, between Martigny and Chamonix, of September 2005. Editorial handling: Stefan Bucher  相似文献   

11.
The fine‐grained (4–11 μm) quartz Optically Stimulated Luminescence (OSL) dating technique was applied to the Weinan section on the southeastern Chinese Loess Plateau (CLP) with a high luminescence sampling resolution (10‐ and 20‐cm intervals). Fifty‐eight OSL ages, spanning c. 1–74 ka, were obtained for the 10‐m loess–palaeosol sequences. The reliability of the OSL dating and the constructed chronology was confirmed by comparing the OSL ages with independent dates from other studies and by correlation with palaeoclimatic time series. The closely spaced OSL ages at Weinan indicate that the mean dust accumulation rate (DAR) of L1–1 (MIS 2, 7.0±0.9 cm ka?1) is lower than those of L1–3 (MIS 4, 19.1±6.1 cm ka?1) and L1–2 (MIS 3, 16.0±0.7 cm ka?1) and that the mean DAR c. 30–20 ka ago (11.4±2.4 cm ka?1) is higher than that c. 20–10 ka ago (3.0±0.1 cm ka?1) in L1–1. The subsequent calculation of the mass accumulation rate (MAR) indicates that the MAR of L1–1 (107 g m?2 a?1) is much lower than those of L1–2 (247 g m?2 a?1) and L1–3 (307 g m?2 a?1). By comparing the mean DAR results during the Last Glacial at Weinan with those at a further six sites from other studies, we observed that the mean DAR of L1–2 is higher (lower) than that of L1–1 on the eastern (western) CLP, and that the mean DAR during MIS 2 has an evident transition from high to low at c. 20 ka on the entire CLP. Possible mechanisms for the above mean DAR changes at orbital and sub‐orbital time scales are presented.  相似文献   

12.
The effect of coal composition, particularly the organic fraction, upon gas sorption has been investigated for Bowen Basin and Sydney Basin, Australia coals. Maceral composition influences on gas retention and release were investigated using isorank pairs of hand-picked bright and dull coal in the rank range of high volatile bituminous (0.78% Ro max) to anthracite (3.01% Ro max). Adsorption isotherm results of dry coals indicated that Langmuir volume (VL) for bright and dull coal types followed discrete, second-order polynomial trends with increasing rank. Bright coals had a minimum VL at 1.72% Ro max and dull coals had a minimum VL at 1.17% Ro max. At low rank, VL was greater in bright coal by about 10 cm3/g, but as rank increased, the bright and dull trends converged and crossed at 1.65% Ro max. At ranks higher than 1.65% Ro max, both bright and dull coals followed similar trends. These competing trends mean that the importance of maceral composition on VL varies according to rank. In high volatile bituminous coals, increases in vitrinite content are associated with increases in adsorption capacity. At ranks higher than medium to low volatile bituminous, changes in maceral composition may exert relatively little influence on adsorption capacity. The Langmuir pressure (PL) showed a strong relationship of decreasing PL with increasing rank, which was not related to coal type. It is suggested that the observed trend is related to a decrease in the heterogeneity of the pore surfaces, and subsequent increased coverage by the adsorbate, as coal rank increases. Desorption rate studies on crushed samples show that dull coals desorb more rapidly than bright coals and that desorption rate is also a function of rank. Coals of lower rank have higher effective diffusivities. Mineral matter was found to have no influence on desorption rate of these finely crushed samples. The evolution of the coal pore structure with changing rank is implicated in diffusion rate differences.  相似文献   

13.
A three-dimensional model for contaminant transport resulting from the dissolution of multicomponent nonaqueous phase liquid (NAPL) pools in three-dimensional saturated subsurface formations is developed. The solution is obtained numerically by a finite-difference scheme, and it is suitable for homogeneous porous media with unidirectional interstitial velocity. Each dissolved component may undergo first-order decay and may sorb under local equilibrium conditions. It is also assumed that the dissolution process is mass transfer limited. The nonaqueous phase activity coefficients of the NAPL pool components are evaluated at each time step. The model behavior is illustrated through a synthetic example with a NAPL pool consisting of a mixture of TCA (1,1,2-trichloroethane) and TCE (trichloroethylene). The numerical solution presented in this work is in good agreement with a recently developed analytical solution for the special case of a single component NAPL pool. The results indicate the importance of accounting for the necessary changes in the organic phase activity which significantly affects the equilibrium aqueous solubility.Notation C liquid phase solute concentration (solute mass/liquid volume) (M L–3) - C s single component aqueous saturation concentration (solubility) (M L–3) - C w equilibrium aqueous solubility (M L–3) - D molecular diffusion coefficient (L2 t –1) - D e effective molecular diffusion coefficient (L2 t –1) - D x longitudinal hydrodynamic dispersion coefficient (L2 t –1) - D y lateral hydrodynamic dispersion coefficient (L2 t –1) - D z hydrodynamic dispersion coefficient in the vertical direction (L2 t –1) - I() integer mode arithmetic operator - k local mass transfer coefficient (Lt –1) - k * average mass transfer coefficient (Lt –1) - L length - l x ,l y pool dimensions inx andy directions (L) - ll x ,l y x andy Cartesian coordinates of the pool origin (L) - M number of moles remaining in a pool (moles) - M initial number of moles (moles) - n finite-difference scheme time level - R retardation factor (dimensionless) - t time (t) - U x average interstitial velocity (Lt –1) - x, y, z spatial Cartesian coordinates (L) - X dimensionless mole fraction - dimensionless activity coefficient - w viscosity of water (=0.8904 cp at 25°C) - decay coefficient (t –1) - * tortuosity ( 1) - i,j, k finite-difference scheme grid indicators - p component number indicator - P total number of components - s pure single component - o nonaqueous phase - w aqueous phase  相似文献   

14.
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15.
Following a large-sized Bhuj earthquake (M s = 7.6) of January 26th, 2001, a small aperture 4-station temporary local network was deployed, in the epicentral area, for a period of about three weeks and resulted in the recording of more than 1800 aftershocks (-0.07 ≤M L <5.0). Preliminary locations of epicenters of 297 aftershocks (2.0 ≤M L <5.0) have brought out a dense cluster of aftershock activity, the center of which falls 20 km NW of Bhachau. Epicentral locations of after-shocks encompass a surface area of about 50 × 40 km2 that seems to indicate the surface projection of the rupture area associated with the earthquake. The distribution of aftershock activity above magnitude 3, shows that aftershocks are nonuniformly distributed and are aligned in the north, northwest and northeast directions. The epicenter of the mainshock falls on the southern edge of the delineated zone of aftershock activity and the maximum clustering of activity occurs in close proximity of the mainshock. Well-constrained focal depths of 122 aftershocks show that 89% of the aftershocks occurred at depths ranging between 6 and 25 km and only 7% and 4% aftershocks occur at depths less than 5 and more than 25 km respectively. The Gutenberg-Richter (GR) relationship, logN = 4.52 - 0.89ML, is fitted to the aftershock data (1.0<-M L<5.0) and theb-value of 0.89 has been estimated for the aftershock activity.  相似文献   

16.
For predicting and forecasting fate of non-conservative pollutants downstream from source using advection–dispersion–decay equation (ADDE), estimation of three parameters; mean flow velocity (U), longitudinal dispersion co-efficient (D L) and decay rate co-efficient (λ), is required a priori. In this three parameters model, estimation of D L holds difficulties and draws interest towards it. The empirical formulae use the field and experimental data of channel and flow characteristics to estimate D L. In this paper, an innovative approach has been proposed towards the estimation of D L using regime channel concept. Having known discharge of flow and silt factor of the riverbed material, hydraulic parameters of the channel can be determined theoretically, which in turn can be used to estimate D L appropriately making use of a suitable empirical formula.  相似文献   

17.
Strong tectonic earthquakes within the crust always occur on already existing faults, and they have the property of a shear rupture. Such earthquakes with surface-wave magnitudes M < 7 obviously have a geometric similarity. Because of this similarity and the validity of the Gutenberg and Richter's energy—magnitude relation, the expression M = 2 log10 L + const., with L = focal length, is valid.The expression LmaxL* for the maximum focal length, is also valid if L* is the length of the rectilinear extent of the seismic line on which the maximum earthquake occurs. The bounds of L* may be given by sharp bends and/or by traversing deep faults. Thus the maximum imaginable earthquake on a seismic line with the length L* has the magnitude Mmax = 2 log10 L* + const.For the investigated region — the Alps and adjacent areas — from the data of recent and historical strong earthquakes, it follows that Mmax = 2 log10 L* + 1.7, if L* is measured in kilometres. These limiting values lie in the centre-field of the magnitude range for maximum earthquakes, published by Shebalin in 1970. By the aid of this equation it is also possible to assess the upper limiting value of the accompanying maximum scale intensity.  相似文献   

18.
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19.
Based on the theory of thermal conductivity, in this paper we derived a formula to estimate the prolongation period （AtL） of cooling-crystallization process of a granitic melt caused by latent heat of crystallization as follows：△tL=QL×△tcol/（TM-TC）×CP where TM is initial temperature of the granite melt, Tc crystallization temperature of the granite melt, Cp specific heat, △tcol cooling period of a granite melt from its initial temperature （TM） to its crystallization temperature （Tc）, QL latent heat of the granite melt.
The cooling period of the melt for the Fanshan granodiorite from its initial temperature （900℃） to crystallization temperature （600℃） could be estimated -210,000 years if latent heat was not considered. Calculation for the Fanshan melt using the above formula yields a AtL value of -190,000 years, which implies that the actual cooling period within the temperature range of 900°-600℃ should be 400,000 years. This demonstrates that the latent heat produced from crystallization of the granitic melt is a key factor influencing the cooling-crystallization process of a granitic melt, prolongating the period of crystallization and resulting in the large emplacement-crystallization time difference （ECTD） in granite batholith.  相似文献   

20.
1IntroductionUp to now,eutrophication is still a problem af-fecting water quality in many developing countries.Themost important nutrients causing eutrophication arephosphates,nitrates and ammonia(Lijklema,1995;Horne and Goldman,1994).Eutrophic waters are…  相似文献   

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