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81.
A parametric study of stability of geotextile-reinforced soil above an underground cavity 总被引:1,自引:1,他引:0
Abbas Tahmasebipoor R. Noorzad E. Shooshpasha A. Barari 《Arabian Journal of Geosciences》2012,5(3):449-456
A study based on two-dimensional finite element analyses under plane strain condition was performed by PLAXIS code to investigate the behavior of geotextile-reinforced soil above an underground cavity. The effects of depth of single layer, tensile stiffness, number and length of reinforcement layers, and size of cavity on settlement of ground surface and head of cavity have been investigated. Results indicated that when a single layer of reinforcement is used, there is a critical depth at which settlements are maximum. Maximum settlements reduce with increase in stiffness of reinforcement. Also settlements reduce with increase in number and length of reinforcement but there is a critical value for number and length of geotextile which increase more than this certain value has not significant effect on reduction of settlements. Also for a given load and tensile stiffness, increase in length of reinforcement has more effect for higher diameter of cavity. 相似文献
82.
Simple, rapid, and sensitive spectrophotometric methods have been proposed for the determination of cationic surfactants (CS) as cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium (DTAB), and cetylpyridinium bromide (CPB). The methods are based on the effects of CSs on the complexes of Al3+ and Be2+ with Chrome Azurol S (CAS). The optimum reaction conditions such as CAS concentration, metal ion concentration, and pH have been studied and found to be 2.0 × 10?4 mol L?1 CAS, 0.5 mg L?1 Al3+ or 0.4 mg L?1 Be2+ and pH 5.4. The analytical characteristics of the methods such as limit of detections, limit of quantifications, and linear ranges have been obtained. CTAB, CPB, and DTAB could be determined by the Al–CAS complex in the ranges of 0.50–40.00, 0.20–10.00, and 0.40–10.00 µmol L?1, and for the Be–CAS complex in the ranges of 0.08–5.00, 0.08–3.00, and 0.20–6.00 µmol L?1, respectively. The limit of the detections of the method for the determination of CTAB, CPB, and DTAB for the Be–CAS complex has been found as 0.025, 0.024, and 0.061 µmol L?1, respectively. The interfering effect of some anions and cations was also tested. The method was applied to the determination of CS CTAB in conditioner shampoo and water samples. 相似文献
83.
New empirical models were developed to predict the soil deformation moduli using gene expression programming (GEP). The principal soil deformation parameters formulated were secant (Es) and reloading (Er) moduli. The proposed models relate Es and Er obtained from plate load-settlement curves to the basic soil physical properties. The best GEP models were selected after developing and controlling several models with different combinations of the influencing parameters. The experimental database used for developing the models was established upon a series of plate load tests conducted on different soil types at depths of 1–24 m. To verify the applicability of the derived models, they were employed to estimate the soil moduli of a part of test results that were not included in the analysis. The external validation of the models was further verified using several statistical criteria recommended by researchers. A sensitivity analysis was carried out to determine the contributions of the parameters affecting Es and Er. The proposed models give precise estimates of the soil deformation moduli. The Es prediction model provides considerably better results in comparison with the model developed for Er. The simplified formulation for Es significantly outperforms the empirical equations found in the literature. The derived models can reliably be employed for pre-design purposes. 相似文献
84.
Seyyed Mohammad Mousavi Amir Hossein Alavi Ali Mollahasani Amir Hossein Gandomi 《Engineering Geology》2011,123(4):324
In this study, new empirical equations were developed to predict the soil deformation moduli utilizing a hybrid method coupling genetic programming and simulated annealing, called GP/SA. The proposed models relate secant (Es), unloading (Eu) and reloading (Er) moduli obtained from plate load–settlement curves to the basic soil physical properties. Several models with different combinations of the influencing parameters were developed and checked to select the best GP/SA models. The database used for developing the models was established upon a series of plate load tests (PLT) conducted on different soil types at various depths. The validity of the models was tested using parts of the test results that were not included in the analysis. The validation of the models was further verified using several statistical criteria. A traditional GP analysis was performed to benchmark the GP/SA models. The contributions of the parameters affecting Es, Eu and Er were analyzed through a sensitivity analysis. The proposed models are able to estimate the soil deformation moduli with an acceptable degree of accuracy. The Es prediction model has a remarkably better performance than the models developed for predicting Eu and Er. The simplified formulations for Es, Eu and Er provide significantly better results than the GP-based models and empirical models found in the literature. 相似文献
85.
Alizadeh BahramAlipour Majid Hosseini S. HossienJahangard A. Abbas 《Organic Geochemistry》2011,42(4):431-437
The Upper Triassic-Middle Jurassic sedimentary succession in the Tabas Basin, with a thickness of about 1600 m, provides a case showing geochemical property changes through the Triassic-Jurassic boundary. The studied section (Kamarmacheh Kuh) is composed of the marine Nayband Formation (Norian-Rhaetian) overlain by siliciclastic sediments of Ab-e-Haji Formation (Lower Jurassic-Aalenian). Detailed geochemical analyses were conducted on selected samples from both formations and the results were used to infer paleo-depositional conditions. Most of the studied samples contain <1 wt% TOC composed mostly of oxidized organic matter with insignificant generative potential. Extract analysis of four representative samples indicate that the rocks also contain minor amounts of preserved algal organic matter along with a secondary contribution of higher plant organic matter from the adjacent watershed. Biomarker analyses show subtle variations in the relative contribution of land plant material that are consistent with the widespread occurrence of coal seams in the upper parts of the Nayband and basal parts of the Ab-e-Haji formations. Although the samples from the Kamarmacheh Kuh Section have low source potential, the extractable hydrocarbons indicate that conditions existed that were conducive to organic matter preservation and that regions of the Tabas Basin with higher primary productivity or lower sedimentation rates may have greater potential. 相似文献
86.
Peyman Afzal Hamid Harati Younes Fadakar Alghalandis Amir Bijan Yasrebi 《Chemie der Erde / Geochemistry》2013
The aim of this study is to identify geochemical anomalies using power spectrum–area (S–A) method based on the grade values of Cu, Mo and Au in 2709 soil samples collected from Kahang porphyry-type Cu deposit, Central Iran. S–A log–log plots indicated that there are three stages of Cu, Mo and Au enrichment. The third enrichment was considered as the main stage for the presence of Cu, Mo and Au at the concentrations above 416 ppm, 23 ppm and 71 ppb, respectively. Elemental anomalies are positively associated with monzo–granite–diorite and breccias units which are in the central and western parts of the deposit. The anomalies are located within the potassic, phyllic and argillic alteration types and also there is the positive correlation between the anomalies and nearing faults in the studied area. The results obtained via fractal model were interpreted accordingly to incorporate the information for the mineralized areas including detailed geological map, structural analysis and alterations. The results show that S–A multifractal modeling is applicable for anomalies delineation based on soil data. 相似文献
87.
Spatially enabled bushfire recovery 总被引:1,自引:0,他引:1
Over the last decade growth in spatial information use for disaster management has been considerable. Maps and spatial data are now recognized as critical elements in each of the four phases of disaster management: mitigation, preparedness, response, and recovery. The use of spatial information to support the phases of mitigation, preparedness and response to bushfires is widely understood. Less attention, however, has been given to the role of spatial information in the recovery. Moreover, the application of the spatially enabled society concept to bushfire recovery has not been explored. This paper explores the role that spatial information plays and could play in the recovery phase of a bushfire disaster. The bushfires in Victoria, Australia that took place during February 2009 are used as the primary case study. It is found that: Spatial information for recovery requires a pre-existing infrastructure; Spatial capacity must be developed across agencies dealing with recovery; Spatially enabled address and parcel information are the key dataset required to support all recovery tasks; Spatial integration of bushfire datasets (spread and intensity) require linking with planning regimes, and Spatial information that is volunteered could be incorporated into recovery activities. 相似文献
88.
Axelle Bouiges Amir Yassin Maya Ikogou Clément Lelarge Axelle-Rolande Sikoa Stefano Mona Michel Veuille 《Comptes Rendus Geoscience》2013,345(7-8):297-305
Previous genetic studies showing evidence of past demographic changes in African drosophilids suggested that these populations had strongly responded to Quaternary climate changes. We surveyed nine species of Zaprionus, a drosophilid genus mostly present in Africa, in forests located between southern Senegal and Gabon. The mitochondrial COI gene showed contrasted levels of sequence variation across species. Populations of the only cosmopolitan species of the genus, Z. indianus, and of its closely related sibling species, Z. africanus, are highly polymorphic and appear to have undergone a continuous population expansion beginning about 130,000 years ago. Five less variable species probably underwent a population expansion beginning only about 20,000–30,000 years ago. One of them, Z. taronus, was significantly structured between forest blocks. The last two species were nearly monomorphic, probably due to infection by Wolbachia. These results are similar to those obtained in three species from the melanogaster subgroup, and may be typical of the responses of African drosophilid populations to glacial cycles. 相似文献
89.
90.
Quantitative and qualitative simulation of groundwater by mathematical models in Rafsanjan aquifer using MODFLOW and MT3DMS 总被引:1,自引:0,他引:1
Agriculture sector by using 80% of freshwater is the greatest water consumer in Iran. Excessive use of agricultural fertilizers in last decade, caused accumulation of enormous amounts of salts and subsequence declined the physical properties of soil. In desert and dry regions such as Rafsanjan plain, use of the groundwater resources is more than the surface water resources. Therefore, information about the quality of these resources remains a necessary task for optimum management, protection of water resources, and stopping the future damages. In this study, the groundwater quantity and quality of Rafsanjan plain was investigated by MODFLOW and MT3DMS. The presented quantitative model for this aquifer was compared by observed data and calibrated. This model was used to predict a 10-year period. Results show that water elevation decreases approximately 15 m for 10 years to come in this plain. Qualitative model results show that most quality parameters will increase. Electrical conductivity will increase more than other parameters. As values of this parameter will reach 16,000 µs/l for next 5 years. Therefore, we suggest that exploitation of water from these resources should be reduced and discharge from some of agricultural wells stop; also we suggested that recharge to groundwater resources should be increased and agricultural activities should be limited or improved using of modern irrigation systems in this plain. 相似文献