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1.
Helical piles are structural deep foundation elements, which can be categorized as torque-driven piles without any limitations to implement in marine situations. Different methods are used to predict the axial capacity of helical piles, such as static analysis, but have some limitation for this type of piles on marine conditions. In situ testing methods as supplement of static analysis have been rarely used for helical piles. In geotechnical engineering practice, the most common in situ tests particularly applicable for coastal or offshore site investigation are cone penetration test (CPT) and piezocone penetration test (CPTu). The CPT is simple, repeatable, and prepares the continuous records of soil layers. In this paper, a data bank has been compiled by collecting the results of static pile load tests on thirty-seven helical piles in ten different sites including CPT or CPTu data. Axial capacities of thirty-seven helical piles in different sites were predicted by direct CPT methods and static analysis. Accuracy estimation of ten direct CPT methods to predict the axial capacity of helical piles was investigated in this study. Comparisons have been made among predicted values and measured capacity from the pile load tests. Results indicated that the recently developed methods such as NGI-05 (2005), ICP-05 (2005), and UWA-05 (2005) predicted axial capacity of helical piles more accurately than the other methods such as Meyerhof (1983), Schmertmann (1978), Dutch (1979), LCPC (1982), or Unicone (1997). However, more investigations are required to establish better correlation between CPT data and axial capacity of helical piles. 相似文献
2.
Mixed estimation methods for Halphen distributions with applications in extreme hydrologic events 总被引：3，自引：1，他引：2
Fateh Chebana Salaheddine El Adlouni Bernard Bobée 《Stochastic Environmental Research and Risk Assessment (SERRA)》2010,24(3):359-376
The Halphen family of distributions is a flexible and complete system to fit sets of observations independent and identically
distributed. Recently, it is shown that this family of distributions represents a potential alternative to the generalized
extreme value distributions to model extreme hydrological events. The existence of jointly sufficient statistics for parameter
estimation leads to optimality of the method of maximum likelihood (ML). Nevertheless, the ML method requires numerical approximations
leading to less accurate values. However, estimators by the method of moments (MM) are explicit and their computation is fast.
Even though MM method leads to good results, it is not optimal. In order to combine the advantages of the ML (optimality)
and MM (efficiency and fast computations), two new mixed methods were proposed in this paper. One of the two methods is direct
and the other is iterative, denoted respectively direct mixed method (MMD) and iterative mixed method (MMI). An overall comparison
of the four estimation methods (MM, ML, MMD and MMI) was performed using Monte Carlo simulations regarding the three Halphen
distributions. Generally, the MMI method can be considered for the three Halphen distributions since it is recommended for
a majority of cases encountered in hydrology. The principal idea of the mixed methods MMD and MMI could be generalized for
other distributions with complicated density functions. 相似文献
3.
Analysis of P wave velocity profiles and seismic data recorded over the 2002 Hydratech cruise conducted in the Storegga region, North of Norway, has shown the existence of anomalies (a velocity decrease) in some layers of the medium. An elastic propagation model is not sufficient to explain clearly these anomalies, since the viscoelastic attenuation, represented by the quality factor QP, is sensitive to physical phenomena of geological media. The combination of the quality factor profile with the velocity profile leads to realistic explanations of these anomalies. In this article, we explain the procedure which we developed for determining the QP profile from the P wave velocity profile and the seismic data recorded during Hydratech cruise. Both the QP and velocity profiles indicate anomalies in the same layers. Based on previous studies, we interpret that these anomalies are being due to existence of gas hydrates and free gas within these layers. 相似文献
4.
Pierre?MasselotEmail author Fateh?Chebana Taha?B.M.J.?Ouarda 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(2):509-522
Regional frequency analysis is an important tool to properly estimate hydrological characteristics at ungauged or partially gauged sites in order to prevent hydrological disasters. The delineation of homogeneous groups of sites is an important first step in order to transfer information and obtain accurate quantile estimates at the target site. The Hosking–Wallis homogeneity test is usually used to test the homogeneity of the selected sites. Despite its usefulness and good power, it presents some drawbacks including the subjective choice of a parametric distribution for the data and a poorly justified rejection threshold. The present paper addresses these drawbacks by integrating nonparametric procedures in the L-moment homogeneity test. To assess the rejection threshold, three resampling methods (permutation, bootstrap and Pólya resampling) are considered. Results indicate that permutation and bootstrap methods perform better than the parametric Hosking–Wallis test in terms of power as well as in time and procedure simplicity. A real-world case study shows that the nonparametric tests agree with the HW test concerning the homogeneity of the volume and the bivariate case while they disagree for the peak case, but that the assumptions of the HW test are not well respected. 相似文献
5.
Serinaldi Francesco Chebana Fateh Kilsby Chris G. 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(5):733-754
Stochastic Environmental Research and Risk Assessment - Investigating the nature of trends in time series is one of the most common analyses performed in hydro-climate research. However, trend... 相似文献
6.
An appraisal of the 1977–1978 regional reconnaissance geochemical data obtained under the Central Belt Project indicated that the Boundary Range Granite, the Senting Granite, and the Benom Igneous Complex appear to constitute favourable uranium exploration targets. Results of the airborne survey subsequently flown within the Project area in 1980 showed high radiometric responses over these and other granitoids. Recent follow-up of a multi-element geochemical anomaly over the Boundary Range Granite has resulted in the discovery of some uraninite-bearing boulders and an abnormally radioactive ironstained quartz vein containing uranium-bearing rhabdophane and florencite. Yet another potential target appears to be the Main Range Granite. Although not within the Project area, it has the distinction of hosting the first recorded uranium occurrence in Peninsular Malaysia.Contrary to earlier belief, the importance of the continental Mesozoic Tembeling and Gagau Groups as possible uranium hosts has been reduced, judging from the poor airborne radiometric response and the overall low geochemical results. On the other hand the Tertiary basins, not previously accorded attention, should be assessed. 相似文献
7.
Weighted estimate of extreme quantile: an application to the estimation of high flood return periods 总被引：1，自引：1，他引：0
Alexandre Lekina Fateh Chebana Taha B. M. J. Ouarda 《Stochastic Environmental Research and Risk Assessment (SERRA)》2014,28(2):147-165
Parametric models are commonly used in frequency analysis of extreme hydrological events. To estimate extreme quantiles associated to high return periods, these models are not always appropriate. Therefore, estimators based on extreme value theory (EVT) are proposed in the literature. The Weissman estimator is one of the popular EVT-based semi-parametric estimators of extreme quantiles. In the present paper we propose a new family of EVT-based semi-parametric estimators of extreme quantiles. To built this new family of estimators, the basic idea consists in assigning the weights to the k observations being used. Numerical experiments on simulated data are performed and a case study is presented. Results show that the proposed estimators are smooth, stable, less sensitive, and less biased than Weissman estimator. 相似文献
8.
ABSTRACTThe clustering of catchments is important for prediction in ungauged basins, model parameterization and watershed development and management. The aim of this study is to explore a new measure of similarity among catchments, using a data depth function and comparing it with catchment clustering indices based on flow and physical characteristics. A cluster analysis was performed for each similarity measure using the affinity propagation clustering algorithm. We evaluated the similarity measure based on depth–depth plots (DD-plots) as a basis for transferring parameter sets of a hydrological model between catchments. A case study was developed with 21 catchments in a diverse New Zealand region. Results show that clustering based on the depth–depth measure is dissimilar to clustering on catchment characteristics, flow, or flow indices. A hydrological model was calibrated for the 21 catchments and the transferability of model parameters among similar catchments was tested within and between clusters defined by each clustering method. The mean model performance for parameters transferred within a group always outperformed those from outside the group. The DD-plot based method was found to produce the best in-group performance and second-highest difference between in-group and out-group performance.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR A. Viglione 相似文献
9.
Ayaz Fateh Ali Cun-de Xiao Xiao-peng Zhang Muhammad Adnan Mudassar Iqbal Garee Khan 《山地科学学报》2018,15(10):2218-2235
Hydrologiska Byrans Vattenbalansavdeling(HBV) Light model was used to evaluate the performance of the model in response to climate change in the snowy and glaciated catchment area of Hunza River Basin. The study aimed to understand the temporal variation of streamflow of Hunza River and its contribution to Indus River System(IRS). HBV model performed fairly well both during calibration(R2=0.87, Reff=0.85, PBIAS=-0.36) and validation(R2=0.86, Reff=0.83, PBIAS=-13.58) periods on daily time scale in the Hunza River Basin. Model performed better on monthly time scale with slightly underestimated low flows period during bothcalibration(R2=0.94, Reff=0.88, PBIAS=0.47) and validation(R2=0.92, Reff=0.85, PBIAS=15.83) periods. Simulated streamflow analysis from 1995-2010 unveiled that the average percentage contribution of snow, rain and glacier melt to the streamflow of Hunza River is about 16.5%, 19.4% and 64% respectively. In addition, the HBV-Light model performance was also evaluated for prediction of future streamflow in the Hunza River using future projected data of three General Circulation Model(GCMs) i.e. BCC-CSM1.1, CanESM2, and MIROCESM under RCP2.6, 4.5 and 8.5 and predictions were made over three time periods, 2010-2039, 2040-2069 and 2070-2099, using 1980-2010 as the control period. Overall projected climate results reveal that temperature and precipitation are the most sensitiveparameters to the streamflow of Hunza River. MIROC-ESM predicted the highest increase in the future streamflow of the Hunza River due to increase in temperature and precipitation under RCP4.5 and 8.5 scenarios from 2010-2099 while predicted slight increase in the streamflow under RCP2.6 during the start and end of the 21 th century. However, BCCCSM1.1 predicted decrease in the streamflow under RCP8.5 due to decrease in temperature and precipitation from 2010-2099. However, Can ESM2 predicted 22%-88% increase in the streamflow under RCP4.5 from 2010-2099. The results of this study could be useful for decision making and effective future strategic plans for water management and their sustainability in the region. 相似文献
10.