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31.
A three-dimensional hybrid model for the analysis of soil-structure interaction under dynamic conditions is developed which takes advantage of the desirable features of the finite element and substructure methods and which minimizes their undesirable features. The modelling is achieved by partitioning the total soil-structure system into a near-field and a far-field with a hemispherical interface. The near-field, which consists of the structure to be analysed and a finite region of soil around it, is modelled by finite elements. The semi-infinite far-field is modelled by distributed impedance functions at the interface which are determined by system identification methods. Numerical results indicate that the proposed model makes possible realistic and economical assessment of three-dimensional soil-structure interaction for both surface and embedded structures. 相似文献
32.
The major advantage of using either the analytic‐signal or the Euler‐deconvolution technique is that we can determine magnetic‐source locations and depths independently of the ambient earth magnetic parameters. In this study, we propose adopting a joint analysis of the analytic signal and Euler deconvolution to estimate the parameters of 2D magnetic sources. The results can avoid solution bias from an inappropriate magnetic datum level and can determine the horizontal locations, depths, structural types (indices), magnetization contrasts and/or structural dips. We have demonstrated the feasibility of the proposed method on 2D synthetic models, such as magnetic contacts (faults), thin dikes and cylinders. However, the method fails to solve the parameters of magnetic sources if there is severe interference between the anomalies of two adjacent magnetic sources. 相似文献
33.
Y-K. Tung K. -C. Yeh 《Stochastic Environmental Research and Risk Assessment (SERRA)》1993,7(2):131-145
Because it can be carried by flowing water, a sand/gravel pit on the river bed could migrate downstream. Consequently, the presence of pits on river beds could pose a safety threat to in-stream hydraulic structures such as bridge piers. A pit migration model can be used to predict progressive changes of pit geometry as it migrates downstream. However, due to the existence of many uncertainties, the maximum pit depth cannot be predicted with certainty. This paper adopted a simple pit migration model and evaluated the uncertainty associated with the calculated maximum pit depth. Such information is essential for evaluating the probability that a migrating pit could pose a safety threat to a downstream hydraulic structure. Three reliability analysis techniques were applied and their performances were compared. 相似文献
34.
Geologic Setting, Field Survey and Modeling of the Chimbote, Northern Peru, Tsunami of 21 February 1996 总被引:1,自引:0,他引:1
J. Bourgeois C. Petroff H. Yeh V. Titov C. E. Synolakis B. Benson J. Kuroiwa J. Lander E. Norabuena 《Pure and Applied Geophysics》1999,154(3-4):513-540
—Whereas the coast of Peru south of 10°S is historically accustomed to tsunamigenic earthquakes, the subduction zone north of 10°S has been relatively quiet. On 21 February 1996 at 21:51 GMT (07:51 local time) a large, tsunamigenic earthquake (Harvard estimate M w = 7.5) struck at 9.6°S, 79.6°W, approximately 130 km off the northern coast of Peru, north of the intersection of the Mendaña fracture zone with the Peru–Chile trench. The likely mechanism inferred from seismic data is a low-angle thrust consistent with subduction of the Nazca Plate beneath the South American plate, with relatively slow rupture characteristics. Approximately one hour after the main shock, a damaging tsunami reached the Peruvian coast, resulting in twelve deaths. We report survey measurements, from 7.7°S to 11°S, on maximum runup (2–5m, between 8 and 10°S), maximum inundation distances, which exceeded 500 m, and tsunami sediment deposition patterns. Observations and numerical simulations show that the hydrodynamic characteristics of this event resemble those of the 1992 Nicaragua tsunami. Differences in climate, vegetation and population make these two tsunamis seem more different than they were. This 1996 Chimbote event was the first large (M w >7) subduction-zone (interplate) earthquake between about 8 and 10°S, in Peru, since the 17th century, and bears resemblance to the 1960 (M w 7.6) event at 6.8°S. Together these two events are apparently the only large subduction-zone earthquakes in northern Peru since 1619 (est. latitude 8°S, est. M w 7.8); these two tsunamis also each produced more fatalities than any other tsunami in Peru since the 18th century. We concur with Pelayo and Wiens (1990, 1992) that this subduction zone, in northern Peru, resembles others where the subduction zone is only weakly coupled, and convergence is largely aseismic. Subduction-zone earthquakes, when they occur, are slow, commonly shallow, and originate far from shore (near the tip of the wedge). Thus they are weakly felt, and the ensuing tsunamis are unanticipated by local populations. Although perhaps a borderline case, the Chimbote tsunami clearly is another wake-up example of a "tsunami earthquake." 相似文献
35.
Chih-Chiang Lu Chu-Hui Chen Tian-Chyi J. Yeh Cheng-Mau Wu I-Fang Yau 《Stochastic Environmental Research and Risk Assessment (SERRA)》2006,20(1-2):6-22
Typhoons and storms have often brought heavy rainfalls and induced floods that have frequently caused severe damage and loss
of life in Taiwan. Our ability to predict sewer discharge and forecast floods in advance during storm seasons plays an important
role in flood warning and flood hazard mitigation. In this paper, we develop an integrated model (TFMBPN) for forecasting
sewer discharge that combines two traditional models: a transfer function model and a back propagation neural network. We
evaluated the integrated model and the two traditional models by applying them to a sewer system of Taipei metropolis during
three past typhoon events (NARI, SINLAKU, and NAKR). The performances of the models were evaluated by using predictions of
a total of 6 h of sewer flow stages, and six different evaluation indices of the predictions. Finally, an overall performance
index was determined to assess the overall performance of each model. Based on these evaluation indices, our analysis shows
that TFMBNP yields accurate results that surpass the two traditional models. Thus, TFMBNP appears to be a promising tool for
flood forecasting for the Taipei metropolis sewer system.
For publication in Stochastic Environmental Research and Risk Analysis. 相似文献
36.
Debra L. Hughson T.-C. Jim Yeh 《Stochastic Environmental Research and Risk Assessment (SERRA)》1998,12(5):285-298
We present a geostatistically based inverse model for characterizing heterogeneity in parameters of unsaturated hydraulic
conductivity for three-dimensional flow. Pressure and moisture content are related to perturbations in hydraulic parameters
through cross-covariances, which are calculated to first-order. Sensitivities needed for covariance calculations are derived
using the adjoint state sensitivity method. Approximations of the conditional mean parameter fields are then obtained from
the cokriging estimator. Correlation between parameters and pressure – moisture content perturbations is seen to be strongly
dependent on mean pressure or moisture content. High correlation between parameters and pressure data was obtained under saturated
or near saturated flow conditions, providing accurate estimation of saturated hydraulic conductivity, while moisture content
measurements provided accurate estimation of the pore size distribution parameter under unsaturated flow conditions. 相似文献
37.
38.
Jing Wu Jian Yin Yonghong Hao Yan Liu Yonghui Fan Xueli Huo Youcun Liu Tian‐Chyi J. Yeh 《水文研究》2015,29(13):2855-2866
The traditional hydrological time series methods tend to focus on the mean of whichever variable is analysed but neglect its time‐varying variance (i.e. assuming the variance remains constant). The variances of hydrological time series vary with time under anthropogenic influence. There is evidence that extensive well drilling and groundwater pumping can intercept groundwater run‐off and consequently induce spring discharge volatility or variance varying with time (i.e. heteroskedasticity). To investigate the time‐varying variance or heteroskedasticity of spring discharge, this paper presents a seasonal autoregressive integrated moving average with general autoregressive conditional heteroskedasticity (SARIMA‐GARCH) model, whose the SARIMA model is used to estimate the mean of hydrological time series, and the GARCH model estimates its time‐varying variance. The SARIMA‐GARCH model was then applied to the Xin'an Springs Basin, China, where extensive groundwater development has occurred since 1978 (e.g. the average annual groundwater pumping rates were less than 0.20 m3/s in the 1970s, reached 1.20 m3/s at the end of the 1980s, surpassed 2.0 m3/s in the 1990s and exceeded 3.0 m3/s by 2007). To identify whether human activities or natural stressors caused the heteroskedasticity of Xin'an Springs discharge, we segmented the spring discharge sequence into two periods: a predevelopment stage (i.e. 1956–1977) and a developed stage (i.e. 1978–2012), and set up the SARIMA‐GARCH model for the two stages, respectively. By comparing the models, we detected the role of human activities in spring discharge volatility. The results showed that human activities caused the heteroskedasticity of the Xin'an Spring discharge. The predicted Xin'an Springs discharge by the SARIMA‐GARCH model showed that the mean monthly spring discharge is predicted to continue to decline to 0.93 m3/s in 2013, 0.67 m3/s in 2014 and 0.73 m3/s in 2015. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
39.
A mathematical model describing the constant pumping is developed for a partially penetrating well in a heterogeneous aquifer system. The Laplace‐domain solution for the model is derived by applying the Laplace transforms with respect to time and the finite Fourier cosine transforms with respect to vertical co‐ordinates. This solution is used to produce the curves of dimensionless drawdown versus dimensionless time to investigate the influences of the patch zone and well partial penetration on the drawdown distributions. The results show that the dimensionless drawdown depends on the hydraulic properties of the patch and formation zones. The effect of a partially penetrating well on the drawdown with a negative patch zone is larger than that with a positive patch zone. For a single‐zone aquifer case, neglecting the effect of a well radius will give significant error in estimating dimensionless drawdown, especially when dimensionless distance is small. The dimensionless drawdown curves for cases with and without considering the well radius approach the Hantush equation (Advances in Hydroscience. Academic Press: New York, 1964) at large time and/or large distance away from a test well. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
40.