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  本文選題：地震液化 + 數(shù)值模擬��； 參考：《大連理工大學(xué)》2014年博士論文

【摘要】：飽和砂土液化在地震中是一種常見現(xiàn)象,易造成場地沉陷、流動等嚴(yán)重災(zāi)害。為研究其致災(zāi)機(jī)理和致災(zāi)程度,數(shù)值模擬可以有效地重現(xiàn)、預(yù)測地震液化過程,是一種省時省力的研究手段。然而,在有限元數(shù)值計算中,由于網(wǎng)格劃分不當(dāng),在動力作用下變形劇烈,出現(xiàn)局部網(wǎng)格扭曲畸變,影響計算效果,甚至中止計算。因此,本文開發(fā)了兩套完整的網(wǎng)格白適應(yīng)方法對該問題進(jìn)行研究,主要分為以下三個方面。 首先,針對液化土體變形特性,采用了基于SPR的誤差評估方法,來展現(xiàn)整個網(wǎng)格應(yīng)變相對誤差的分布。將雙線性回歸函數(shù)應(yīng)用于三角形單元的網(wǎng)格,比常規(guī)線性回歸函數(shù)獲得了更穩(wěn)定、更準(zhǔn)確的誤差分布,可精確指導(dǎo)局部網(wǎng)格細(xì)化或再生成,也適用于四邊形和三角形單元的混合網(wǎng)格。 其次,分別開發(fā)了基于相似形分裂的網(wǎng)格細(xì)化方案和基于Delaunay三角剖分的網(wǎng)格再生成方案。通過測試和討論,將與液化程度相關(guān)的平均相對誤差設(shè)定為合適的自適應(yīng)誤差閾值,以實現(xiàn)局部網(wǎng)格的有限次合理加密。 最后,對應(yīng)局部網(wǎng)格細(xì)化和再生成的方案,分別建立了與之匹配的新舊網(wǎng)格數(shù)據(jù)傳遞系統(tǒng)。在充分利用有限元基本規(guī)則的同時,將土體材料的塑性特征完整地從舊網(wǎng)格中繼承到新網(wǎng)格中,實現(xiàn)了網(wǎng)格自適應(yīng)流程中數(shù)據(jù)的準(zhǔn)確續(xù)算。 在進(jìn)行上述三個方面的過程中,也探索了兩種網(wǎng)格自適應(yīng)方案的適用范圍和可靠性,獲得并整理了他們的優(yōu)勢和缺陷。 通過上述工作,證明了網(wǎng)格自適應(yīng)方案在地震液化數(shù)值模擬中能夠精確地捕捉并平滑尖銳變形,極大地避免網(wǎng)格扭曲畸變；在有目標(biāo)地、合理有序地加密局部網(wǎng)格的基礎(chǔ)上降低整體計算的誤差,與一致性加密的網(wǎng)格相比節(jié)省了大量計算資源,改善了常規(guī)有限元的數(shù)值結(jié)果,進(jìn)一步發(fā)揮了基于網(wǎng)格計算的有限元方法的高效性。
[Abstract]:Saturated sand liquefaction is a common phenomenon in earthquakes, which can easily cause site subsidence, flow and other serious disasters.In order to study the mechanism and degree of earthquake liquefaction, numerical simulation can effectively reproduce and predict the process of earthquake liquefaction, which is a time-saving and labor-saving research method.However, in the finite element numerical calculation, due to the improper mesh division, the deformation is severe under the dynamic action, and the local mesh distortion appears, which affects the calculation effect and even suspends the calculation.Therefore, this paper develops two complete grid white adaptation methods to study the problem, mainly divided into the following three aspects.Firstly, according to the deformation characteristics of liquefaction soil, an error evaluation method based on SPR is adopted to show the relative error distribution of the whole grid strain.The bilinear regression function is applied to the mesh of triangular element, which is more stable and accurate than the conventional linear regression function, and can precisely direct the local mesh refinement or regeneration.It also applies to mixed meshes of quadrilateral and triangular elements.Secondly, a mesh refinement scheme based on similar shape splitting and a mesh regeneration scheme based on Delaunay triangulation are developed respectively.Through testing and discussing, the average relative error related to the degree of liquefaction is set as the appropriate adaptive error threshold to realize the finite reasonable encryption of the local mesh.Finally, corresponding to the scheme of local mesh refinement and regeneration, the matching new and old grid data transfer systems are established.At the same time, the plastic characteristics of soil materials are inherited from the old mesh to the new mesh completely, and the data in the adaptive mesh flow is accurately continued.In the process of the above three aspects, the applicability and reliability of the two mesh adaptive schemes are also explored, and their advantages and disadvantages are obtained and sorted out.Through the above work, it is proved that the mesh adaptive scheme can accurately capture and smooth sharp deformation in the numerical simulation of seismic liquefaction, and greatly avoid the distortion of mesh distortion.On the basis of reasonably and orderly encrypting local meshes, the error of global computation is reduced. Compared with the uniformly encrypted grids, the computational resources are saved and the numerical results of the conventional finite element method are improved.The high efficiency of the finite element method based on grid computing is further brought into play.
【學(xué)位授予單位】：大連理工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TU441;TU435

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相關(guān)期刊論文 前10條

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本文編號：1733619