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软土地下工程抗震数值模拟的若干关键问题 总被引:1,自引:0,他引:1
针对我国地下工程建设项目抗震安全性能设计和评估的需求,并基于目前缺少完善的地下结构抗震分析方法和专门的地下结构抗震设计规范的现状,重点阐述了采用有限元方法进行地下工程数值模拟和分析时需要特别关注的三方面问题:计算范围、土一结构动力相互作用和边界条件。着重分析了有限元网格的划分、土一结非线性接触问题和不同边界条件的适用性,以及这些建模条件对计算结果可靠性的影响。对基于数值手段开展地下工程抗震安全性能的计算、分析和评价,制定地下结构抗震设计规范或规程,可提供有益参考。 相似文献
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利用卫星观测OLR资料以及海气耦合数值模拟试验结果,从每年波-频分析结果提取了各种传播模态的强度指数序列,分析了热带北半球夏季季节内振荡(BSISO)各种传播模态的年际变化谱特征,探讨了热带各海区海气相互作用对其影响。主要结果如下:赤道外西传波和印度洋北传波以准2 a为显著振荡周期,赤道东传波、南海北传波和西太平洋北传波则都包含准2 a和准5 a两种周期,南海北传波是5种指数中惟一以准5 a为最主要周期振荡的模态。热带印度洋、西太平洋、东太平洋各海区海气相互作用对各指数准2 a振荡、准5 a振荡既有加强作用,也有削弱作用。各海区比较而言,对赤道东传波准2 a和准5 a振荡、南海北传波准2 a和准5 a振荡起最大加强作用的是西太平洋海区海气相互作用;对赤道外西传波准2 a振荡、西太平洋北传波准2 a和准5 a振荡起最大加强作用的是印度洋海区海气相互作用。 相似文献
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In order to investigate surf zone hydrodynamics through two-dimensional numerical simulations of nearshore circulation under random wave environment, a nearshore circulation model, SHORECIRC, and a random wave model, SWAN, were combined and utilized. Using this combined model, a numerical simulation of the October 2, 1997 SandyDuck field experiment was performed. For this simulation, field topography and an input offshore spectrum were constructed using observed data sets synchronized with the experiment. The wave-breaking model in SWAN was modified by using breaker parameters varied according to bottom slope. The simulation results were compared with the experimental data, which revealed a well-developed longshore current, as well as with results using other combinations which were SHORECIRC and its original monochromatic wave-driver, and SHORECIRC and the default of SWAN. The results from the novel combined model agreed well with the experimental data. The results of the present simulation also indicate that alongshore field topography influences shear fluctuation of longshore currents. 相似文献
96.
Numerical studies of methane production from Class 1 gas hydrate accumulations enhanced with carbon dioxide injection 总被引:2,自引:0,他引:2
Class 1 gas hydrate accumulations are characterized by a permeable hydrate-bearing interval overlying a permeable interval with mobile gas, sandwiched between two impermeable intervals. Depressurization-induced dissociation is currently the favored technology for producing gas from Class 1 gas hydrate accumulations. The depressurization production technology requires heat transfer from the surrounding environment to sustain dissociation as the temperature drops toward the hydrate equilibrium point and leaves the reservoir void of gas hydrate. Production of gas hydrate accumulations by exchanging carbon dioxide with methane in the clathrate structure has been demonstrated in laboratory experiments and proposed as a field-scale technology. The carbon dioxide exchange technology has the potential for yielding higher production rates and mechanically stabilizing the reservoir by maintaining hydrate saturations. We used numerical simulation to investigate the advantages and disadvantages of using carbon dioxide injection to enhance the production of methane from Class 1 gas hydrate accumulations. Numerical simulations in this study were primarily concerned with the mechanisms and approaches of carbon dioxide injection to investigate whether methane production could be enhanced through this approach. To avoid excessive simulation execution times, a five-spot well pattern with a 500-m well spacing was approximated using a two-dimensional domain having well boundaries on the vertical sides and impermeable boundaries on the horizontal sides. Impermeable over- and under burden were included to account for heat transfer into the production interval. Simulation results indicate that low injection pressures can be used to reduce secondary hydrate formation and that direct contact of injected carbon dioxide with the methane hydrate present in the formation is limited due to bypass through the higher permeability gas zone. 相似文献
97.
Masanori Kurihara Akihiko SatoKunihiro Funatsu Hisanao OuchiYoshihiro Masuda Hideo NaritaTimothy S. Collett 《Marine and Petroleum Geology》2011,28(2):502-516
Targeting the methane hydrate (MH) bearing units C and D at the Mount Elbert prospect on the Alaska North Slope, four MDT (Modular Dynamic Formation Tester) tests were conducted in February 2007. The C2 MDT test was selected for history matching simulation in the MH Simulator Code Comparison Study. Through history matching simulation, the physical and chemical properties of the unit C were adjusted, which suggested the most likely reservoir properties of this unit. Based on these properties thus tuned, the numerical models replicating “Mount Elbert C2 zone like reservoir”, “PBU L-Pad like reservoir” and “PBU L-Pad down dip like reservoir” were constructed. The long term production performances of wells in these reservoirs were then forecasted assuming the MH dissociation and production by the methods of depressurization, combination of depressurization and wellbore heating, and hot water huff and puff. The predicted cumulative gas production ranges from 2.16 × 106 m3/well to 8.22 × 108 m3/well depending mainly on the initial temperature of the reservoir and on the production method.This paper describes the details of modeling and history matching simulation. This paper also presents the results of the examinations on the effects of reservoir properties on MH dissociation and production performances under the application of the depressurization and thermal methods. 相似文献
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