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51.
The aim of this study is to develop a two-dimensional hydrodynamic tidal model for the Persian Gulf (PG2017) using 2D-MIKE21 software. The advantages of present study is accounting for the spatial variation of bed friction coefficient besides a precise bathymetry together with a 23-year of combined records of satellite altimetry data. We found that the bed friction coefficient has a significant effect on sea level changes in the region under our modeling consideration. Since the tidal behavior in the northern part of the Qeshm Island is significantly different from the other parts of the Persian Gulf, to present a more accurate hydrodynamic tidal model, the Gulf is divided into two regions where the bed friction coefficient is modeled separately for each region. The root mean square value of the differences between the amplitude of dominant constituents; M2, S2, K1, and O1 derived from the PG2017 model and that of 98 altimetry and coastal tide gauge stations are respectively equal to 1.6, 1.9, 2.8, and 1.3?cm. Moreover, comparing the PG2017 model efficiency with the FES2014, OSU12, EOT11a, DTU10, and Admiralty models shows that the PG2017 model has an improvement of 22.1%, 47.2%, 43.2%, 44.2%, and 57.6% in terms of relative error, respectively.  相似文献   
52.
In the linear seismic design of buildings, the (deterministic) substructure method is a customary and efficient approach. However, the existence of spatial variability in the parameters of the mechanical model of the soil, as well as parametric errors, calls for the use of probabilistic approaches in order to provide a reliable design of the structure. The construction of probabilistic models of the soil impedance matrix provides a natural path to such approaches within the context of the substructure method. Two main techniques are described in this paper: a parametric one, typically using the stochastic finite element method, and a nonparametric one, which was introduced more recently. The latter is explored more specifically, and the possibilities it offers in terms of seismic design are presented. In particular, it is shown that it allows for the estimation of quantiles of the quantities of interest, rather than confidence intervals, which lead to highly conservative design. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   
53.
In the practice of geotechnical engineering, the case of a ring footing carrying a set of concentrated point loads is a common problem. At times, the induced vertical and angular displacements for the ring footing need to be evaluated at a relatively precise level. By making use of the governing set of equations derived for the case of a general curved beam, expressions that can be easily implemented in modern computing software are derived for the vertical and angular displacements of a ring footing of rectangular cross section as functions of the radial position. The loading case considered is a vertical point load, and the soil is modelled as elastic. Estimates of the displacements have been shown for a common range of practical applications. The behaviour for a set of concentrated loads may be evaluated using the derived equations through direct superposition. Nonlinear finite element analysis is used to evaluate the vertical deflection and angular twist of the ring foundation. Numerical analysis performed for three ring foundations with different radii and cross sections is reported to validate the accuracy of the derived analytical solution. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
54.
We propose a numerical method that couples a cohesive zone model (CZM) and a finite element‐based continuum damage mechanics (CDM) model. The CZM represents a mode II macro‐fracture, and CDM finite elements (FE) represent the damage zone of the CZM. The coupled CZM/CDM model can capture the flow of energy that takes place between the bulk material that forms the matrix and the macroscopic fracture surfaces. The CDM model, which does not account for micro‐crack interaction, is calibrated against triaxial compression tests performed on Bakken shale, so as to reproduce the stress/strain curve before the failure peak. Based on a comparison with Kachanov's micro‐mechanical model, we confirm that the critical micro‐crack density value equal to 0.3 reflects the point at which crack interaction cannot be neglected. The CZM is assigned a pure mode II cohesive law that accounts for the dependence of the shear strength and energy release rate on confining pressure. The cohesive shear strength of the CZM is calibrated by calculating the shear stress necessary to reach a CDM damage of 0.3 during a direct shear test. We find that the shear cohesive strength of the CZM depends linearly on the confining pressure. Triaxial compression tests are simulated, in which the shale sample is modeled as an FE CDM continuum that contains a predefined thin cohesive zone representing the idealized shear fracture plane. The shear energy release rate of the CZM is fitted in order to match to the post‐peak stress/strain curves obtained during experimental tests performed on Bakken shale. We find that the energy release rate depends linearly on the shear cohesive strength. We then use the calibrated shale rheology to simulate the propagation of a meter‐scale mode II fracture. Under low confining pressure, the macroscopic crack (CZM) and its damaged zone (CDM) propagate simultaneously (i.e., during the same loading increments). Under high confining pressure, the fracture propagates in slip‐friction, that is, the debonding of the cohesive zone alternates with the propagation of continuum damage. The computational method is applicable to a range of geological injection problems including hydraulic fracturing and fluid storage and should be further enhanced by the addition of mode I and mixed mode (I+II+III) propagation. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   
55.
采用二维水深平均方程组作为控制方程,利用边界拟合法进行坐标变换,采用有限体积法计算反调节水库的流场。在计算中,由于已知上游泵站抽水流量及下游枢纽供水流量,且上下游均找不到水位流量关系,上下游边界均为流速边界条件,没有压力边界条件,解不惟一,所以采用全水库水量平衡方程作为补充方程来补充定解条件。  相似文献   
56.
FLATModel is a two-dimensional shallow-water approximation code with corrections and modifications that create a simulation tool adapted to debris-flows behaviour. FLATModel uses the finite volume method with the numerical implementation of the Godunov scheme and includes correction terms regarding the effect of flow over high slopes and curvature. Additionally, the stop-and-go phenomenon, the basal entrainment and a correction regarding the front inclination of the final deposit are incorporated into FLATModel. In addition, different flow resistance laws were integrated in the numerical code including Bingham, Herschel–Bulkley and Voellmy fluid model. Firstly, our numerical model was validated using analytical solutions of a dam-break scenario and published data on a laboratory experiment. Secondly, three real events, which occurred in the northeastern part of the Iberian Peninsula, were back-calculated. Although field observations of the three events are not very detailed, the back-analyses revealed interesting patterns on the flow dynamics, and the numerical results generally showed good agreement with field data. Comparing the different flow resistance laws, the Voellmy fluid model presents the best behaviour regarding both the flow behaviour and the deposit characteristics. Preliminary simulation runs incorporating the effect of basal entrainment offered satisfactory results, although the final volume is rather sensitive on the selected friction angle of channel-bed material. The outcomes regarding the correction of the calculated front inclination of the final deposit showed that this implementation strongly improves the simulation results and better represents steep fronts of final deposits.  相似文献   
57.
大型整体式贮煤筒仓基础有限元分析   总被引:2,自引:0,他引:2  
采用有限元分析了不同土体的弹性本构关系和不同堆煤荷载施加方式对筒仓基础的影响;在此基础上分析了煤压力、桩土之间的接触压力、桩的内力与变形、土体沉降等变化规律。从计算结果可知,考虑土体的弹性模量随土层的压实而提高,并考虑煤与筒仓、基础土体之间的相互作用,使得筒仓基础的受力状态与实际情况更接近,从而得到优化的筒仓基础设计。  相似文献   
58.
Uncontrolled coal fires are natural disasters that may cause mineral loss and environmental damage. The traditional loop source transient electromagnetic method can effectively detect the low-resistivity region of coal fires, but its detection efficiency is not so good for high-resistivity regions. In view of this limitation, a technique based on electrical source transient electromagnetics is proposed in this paper to detect high-resistivity regions in the spontaneous combustion process of coal. Considering the complex geometry of the coal fire area, an unstructured tetrahedral grid is used in this study to realize the spatial discretization of the model, and solve the electromagnetic field based on a vector finite element algorithm. Numerical analysis is used to investigate methods for detecting coal fires and the characteristics of effective anomalies are further examined to provide guidance for practical detection.  相似文献   
59.
吕宋海峡输送年际变异数值研究   总被引:1,自引:0,他引:1  
利用MITgcm数值模式1980—2001年的常规模拟输出数据,研究了吕宋海峡22年平均的体积、热量和盐量输送随深度的变化,并利用小波变换分别分析了吕宋海峡3个层次(0—145、145—915、915—1 837m)体积和热量输送的年际变化,主要结果如下。(1)在吕宋海峡1 837m层以下,仍有一定数量的西北太平洋海水(体积和盐)西向输送到南海;(2)915—1 615m层的年际体积输送的变化趋势与上两个层次(0—145m、145—915m)类似,但是在某些ENSO时期(如1985、1987、1991—1995年),其年际变化与145—915m层年际变化的位相相反;(3)吕宋海峡年际体积(热量)输送的小波谱图较明显地反映出ENSO现象对吕宋海峡不同层次的输送均产生一定影响。145—915m层次的吕宋海峡年际体积输送与ENSO现象相关性显著。  相似文献   
60.
丁选明  刘汉龙 《岩土力学》2006,27(Z2):784-790
现浇薄壁管桩是一种大直径的管桩,在低应变检测时必然存在平截面假定不满足以及桩头三维效应的问题。无桩帽管桩低应变检测时由于激发了非轴对称的弯曲模态,并不是达到一定的深度平截面假定就会满足,各截面不同的点会受到不同程度的高频干扰,桩顶90°点受到了较小的高频干扰,低应变检测时激振点与传感器夹角为90°时更容易得到清晰的反射波信号。解析解和有限元解的结果均表明,带帽桩在桩帽的动力响应信号能看到明显的桩底反射和缺陷反射时距离桩心不同点上所感受的高频干扰的频率一样,速度振幅不同,距桩心0.50 ( 为桩半径)的点受到最小的干扰。  相似文献   
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