The effects of method of generating circular slip surfaces on determining the critical slip surface by particle swarm optimization   总被引：1，自引：0，他引：1  

R. Kalatehjari  N. Ali  M. Kholghifard  M. Hajihassani 《Arabian Journal of Geosciences》2014,7(4):1529-1539

The main objectives of slope stability analysis are evaluating factor of safety for a given slip surface and determining the critical slip surface for a given slope. Factor of safety is usually calculated by limit equilibrium method. The main steps to determine the critical slip surface are generating trial slip surfaces as probable solutions and searching among them to determine the one with the lowest factor of safety. Although the process of searching the critical slip surface received much attention between researchers, the significance of method of generating slip surfaces is seldom addressed in the literature. The authors believe that this ignorance can affect the accuracy of the results of slope stability analysis even in the simplest problems with circular slip surfaces. Consequently, this paper focused on the method of generating circular trial slip surfaces as the simplest mechanism of sliding and considered its effect on determining the critical slip surface. A new method of generating circular slip surface was presented, which is more efficient and less restricted than the conventional method. A computer program was also developed to determine the critical slip surface of slopes by using particle swarm optimization. The performances of the proposed method and developed computer program were verified during comparative studies and sensitivity analysis. Based on the results, the effect of method of generating circular slip surfaces on determining the critical slip surface was confirmed successfully. In all considered problems, the proposed method of generating circular slip surfaces led to the lower values of factor of safety compare with the conventional method.  相似文献   

Geoelectric model and hydrochemistry of salinity affected lower Atrai floodplain aquifer,NW Bangladesh: An approach for irrigation management     

Q. H. Mazumder  C. S. Jahan  F. Mazumder  M. A. Islam  S. Jaman  M. N. Ali  A. T. M. S. Rahaman  M. R. Arefin  A. Ahasan 《Journal of the Geological Society of India》2014,84(4):431-441

In the salinity affected lower Atrai floodplain aquifer in the NW Bangladesh, geoelectric resistivity survey and hydrochemical analysis are carried out with an aim to identify fresh and saline groundwater zones; investigate the status of salinity; evaluate hydrochemical processes involved and suggest management approaches for irrigation. Here a two-fold aquifer system, inter-layered by silt, clay and silty-clay aquitard and aquiclude is classified as: upper aquifer — spatially affected by salinity of varying degrees; and lower aquifer — generally characterized by high salinity. The aquifer with resistivity values greater than 69 Ωm is safe for irrigation use. Concentrations of major ions vary as: Ca²⁺>Na⁺>Mg²⁺>K⁺ and HCO₃>Cl>NO₃>SO₄ ^2?. Groundwater is dominated by Na-Ca to Ca-Na, HCO₃-Cl-SO₄, Cl-SO₄-HCO₃ and Cl-SO₄ ^2? facies where Ca²⁺, Mg²⁺, SO₄ ^2?, HCO₃ ^?, Cl^? and NO₃ ^2? ion concentrations are statistically dominant and water is of Ca-Mg, HCO₃-SO₄-Cl and NO₃ types. Geochemically, groundwater is hard and saline to fresh water type. Salinity increases with depth, but spatially towards the southern part. Groundwater quality is a product of water-rock interaction, direct mixing and marine spraying, or fall-out of airborne marine salts, where silicate weathering is the primary source of bivalent cations. Sediment provenance of alkaline earth silicates and higher concentrations of alkalis are derived from sources other than precipitation. In general partially or fully salinity affected upper and lower aquifers in the area except in its eastern part are not suitable for tubewell irrigation. As groundwater demand for irrigation is increasing, the saline water has progressively invaded relatively fresher parts of the aquifer by upconning. So, special salinity control management approaches can be adopted through engineering techniques such as groundwater abstraction optimization, as also through scientific behavioral approaches like groundwater demand management, salt tolerant crops production. In this context, surface water conservation and rain water harvesting for domestic and irrigational uses are recommended in the salinity affected area.  相似文献   

Effects of Shear Rate on Cyclic Loading Shear Behaviour of Rock Joints Under Constant Normal Stiffness Conditions     

Ali Mirzaghorbanali  Jan Nemcik  Naj Aziz 《Rock Mechanics and Rock Engineering》2014,47(5):1931-1938

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Investigating the Economic Performance of Tunnel Excavation in Iran: 1998–2013     

Vahid Karkehabadi  Hamidreza Zarei  Ali Uromeihy  Hamidreza Karkehabadi 《Geotechnical and Geological Engineering》2014,32(5):1353-1362

Nowadays, the world is witnessing the ever increasing need of Tunnel excavation due to their unique features and the kind of human applied plans. This has led to increase in demand of excavating this engineering factor. Tunnel excavation process faces a lot of challenges due to environmental and technological complexities which causes the economic evaluation and investigation of this project to be difficult. It is tried to develop the proposed model with regard to efficiency concept in order to evaluate and investigate the efficiency of relative economic performance of Tunnel excavation projects and turn to its modeling and implementing by data envelopment analysis and Fuzzy DEMATEL techniques. The results in Iran showed that the proposed model can turn to investigation and evaluation of economic efficiency of Tunnel excavation by considering two optimistic (ideal) and pessimistic perspectives such that the Tunnel excavation process of “Karaj water transition” and “Cheshmelangan water transition” among 12 rock Tunnel excavation projects of Iran in the time period of 1998–2013 were respectively introduced as the most efficient and the most inefficient rock Tunnel excavation projects.  相似文献   

An Elasto-Plastic Constitutive Model for Rock Joints Under Cyclic Loading and Constant Normal Stiffness Conditions   总被引：1，自引：1，他引：0  

Jan Nemcik  Ali Mirzaghorbanali  Naj Aziz 《Geotechnical and Geological Engineering》2014,32(2):321-335

An elasto-plastic constitutive model is introduced for rock joints under cyclic loading, considering the additional shear resistance generated by the asperity damage in the first forward shear cycle and sliding mechanism for further shearing. A series of cyclic loading direct shear tests was conducted on artificial joints with triangular asperities and replicas of a real rock asperity surface under constant normal stiffness (CNS) conditions. The model was calibrated and then validated using selected data sets from the experimental results. Model simulations were found to be in good agreement with the rock joints behaviour under cyclic loading and CNS conditions both in stress prediction and dilation behaviour. In addition, dynamic stability analysis of an underground structure was carried out, using Universal Distinct Element Code and the proposed constitutive model.  相似文献   

An alternative method for non-negative estimation of variance components   总被引：1，自引：1，他引：0  

Khosro Moghtased-Azar  Ramin Tehranchi  Ali Reza Amiri-Simkooei 《Journal of Geodesy》2014,88(5):427-439

A typical problem of estimation principles of variance and covariance components is that they do not produce positive variances in general. This caveat is due, in particular, to a variety of reasons: (1) a badly chosen set of initial variance components, namely initial value problem (IVP), (2) low redundancy in functional model, (3) an improper stochastic model, and (4) data’s possibility of containing outliers. Accordingly, a lot of effort has been made in order to design non-negative estimates of variance components. However, the desires on non-negative and unbiased estimation can seldom be met simultaneously. Likewise, in order to search for a practical non-negative estimator, one has to give up the condition on unbiasedness, which implies that the estimator will be biased. On the other hand, unlike the variance components, the covariance components can be negative, so the methods for obtaining non-negative estimates of variance components are not applicable. This study presents an alternative method to non-negative estimation of variance components such that non-negativity of the variance components is automatically supported. The idea is based upon the use of the functions whose range is the set of all positive real numbers, namely positive-valued functions (PVFs), for unknown variance components in stochastic model instead of using variance components themselves. Using the PVF could eliminate the effect of IVP on the estimation process. This concept is reparameterized on the restricted maximum likelihood with no effect on the unbiasedness of the scheme. The numerical results show the successful estimation of non-negativity estimation of variance components (as positive values) as well as covariance components (as negative or positive values).  相似文献   

New data on the Late Cenozoic basaltic volcanism in Syria,applied to its origin     

V.G. Trifonov  A.E. Dodonov  E.V. Sharkov  D.I. Golovin  I.V. Chernyshev  V.A. Lebedev  T.P. Ivanova  D.M. Bachmanov  M. Rukieh  O. Ammar  H. Minini  A.-M. Al Kafri  O. Ali 《Journal of Volcanology and Geothermal Research》2011,199(3-4):177-192

New data on geology and 21 K–Ar dates of the Late Oligocene–Quaternary basalts in Syria, combined with analysis of the new and previous data are used to reconstruct the volcanic history and relations between it and tectonic events. Volcanism began at the end of Oligocene (26–24 Ma) and was concentrated in the Late Oligocene–Early Miocene along a N-trending band, which stretches from the Jebel Arab (Harrat Ash Shaam) up to Kurd Dagh and southern Turkey. Activity waned in the Middle Miocene (17–12 Ma), but was resumed in the same band in the Tortonian and increased in the Messinian and Early Pliocene (6.3–4 Ma), when volcanism spread to the Shin Plateau and its coastal extension. After a brief hiatus ～ 4–3.5 Ma, volcanism became still more intensive and spread from the N-trending band to the east into the northern margin of the Mesopotamian Foredeep and to the west into the Dead Sea Transform zone. Additional eruptions continued into the Holocene.Volcanism lasted > 25 million years in the Jebel Arab Highland and > 15 million years in the Aleppo Plateau. The long duration of volcanism in the same parts of the moving Arabian plate and absence of records of one-way migration of the activity mean that the magmatic sources moved together with the plate, i.e., they were situated within the lithosphere mantle. Coincidence of the tectonic and volcanic stages of the Arabian plate development proves that volcanic activity depended on the geodynamic situation, caused by the plate motion. Situated within the lithosphere, magmatic sources within this transverse band were possibly caused by thermal and deforming influences of the asthenospheric lateral flow, moved laterally from the Ethiopia–Afar deep superplume.  相似文献   

An enhanced constitutive model for crushable granular materials     

Ali Daouadji  Pierre‐Yves Hicher 《国际地质力学数值与分析法杂志》2010,34(6):555-580

Studies in the past have tried to reproduce the mechanical behaviour of granular materials by proposing constitutive relations based on a common assumption that model parameters and parameters describing the properties, including gradation of individual grains are inevitably linked. However successful these models have proved to be, they cannot account for the changes in granular assembly behaviour if the grains start to break during mechanical loading. This paper proposes to analyse the relation between grading change and the mechanical behaviour of granular assembly. A way to model the influence of grain breakage is to use a critical state‐based model. The influence of the amount of grain breakage during loading, depending on the individual grain strength and size distribution, can be introduced into constitutive relations by means of a new parameter that controls the evolution of critical state with changes in grain size distribution. Experimental data from a calcareous sand, a quartz sand, and a rockfill material were compared with numerical results and good‐quality simulations were obtained. The main consequences of grain breakage are increased compressibility and a gradual dilatancy disappearance in the granular material. The critical state concept is also enriched by considering its overall relation to the evolution of the granular material. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Fisher Matrix-based Predictions for Measuring the <Emphasis Type="Italic">z</Emphasis> = 3.35 Binned 21-cm Power Spectrum using the Ooty Wide Field Array (OWFA)     

Anjan Kumar Sarkar  Somnath Bharadwaj  Sk. Saiyad Ali 《Journal of Astrophysics and Astronomy》2017,38(1):14

We use the Fisher matrix formalism to predict the prospects of measuring the redshifted 21-cm power spectrum in different k-bins using observations with the upcoming Ooty Wide Field Array (OWFA) which will operate at 326.5 MHz. This corresponds to neutral hydrogen (HI) at z = 3.35, and a measurement of the 21-cm power spectrum provides a unique method to probe the large-scale structures at this redshift. Our analysis indicates that a 5σ detection of the binned power spectrum is possible in the k range 0.05 ≤ k ≤ 0.3 Mpc^?1 with 1000 hours of observation. We find that the signal- to-noise ratio (SNR) peaks in the k range 0.1?0.2 Mpc^?1 where a 10σ detection is possible with 2000 hours of observations. Our analysis also indicates that it is not very advantageous to observe beyond 1000 h in a single field-of-view as the SNR increases rather slowly beyond this in many of the small k-bins. The entire analysis reported here assumes that the foregrounds have been completely removed.  相似文献   

Geochemical and oxygen isotope perspective of a new R chondrite Dhofar 1671: Affinity with ordinary chondrites          下载免费PDF全文

Arshad Ali  Sobhi J. Nasir  Iffat Jabeen  Ahmed Al Rawas  Neil R. Banerjee  Gordon R. Osinski 《Meteoritics & planetary science》2017,52(9):1991-2003

Dhofar 1671 is a relatively new meteorite that previous studies suggest belongs to the Rumuruti chondrite class. Major and REE compositions are generally in agreement with average values of the R chondrites (RCs). Moderately volatile elements such as Se and Zn abundances are lower than the R chondrite values that are similar to those in ordinary chondrites (OCs). Porphyritic olivine pyroxene (POP), radial pyroxene (RP), and barred olivine (BO) chondrules are embedded in a proportionately equal volume of matrix, one of the characteristic features of RCs. Microprobe analyses demonstrate compositional zoning in chondrule and matrix olivines showing Fa‐poor interior and Fa‐rich outer zones. Precise oxygen isotope data for chondrules and matrix obtained by laser‐assisted fluorination show a genetic isotopic relationship between OCs and RCs. On the basis of our data, we propose a strong affinity between these groups and suggest that OC chondrule precursors could have interacted with a ¹⁷O‐rich matrix to form RC chondrules (i.e., ?¹⁷O shifts from ~1‰ to ~3‰). These interactions could have occurred at the same time as “exotic” clasts in brecciated samples formed such as NWA 10214 (LL3–6), Parnallee (LL3), PCA91241 (R3.8–6), and Dhofar 1671 (R3.6). We also infer that the source of the oxidation and ¹⁷O enrichment is the matrix, which may have been enriched in ¹⁷O‐rich water. The abundance of matrix in RCs relative to OCs, ensured that these rocks would be apparently more oxidized and appreciably ¹⁷O‐enriched. In situ analysis of Dhofar 1671 is recommended to further strengthen the link between OCs and RCs.  相似文献