共查询到19条相似文献,搜索用时 62 毫秒
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非饱和土中溶质迁移参数反演的HISR方法 总被引:1,自引:0,他引:1
以非饱和土中溶质迁移参数反演问题为背景, 依据正则化方法的思路, 以Itakura Saito距离作为同伦函数中的平凡问题, 将同伦方法引入非线性参数反演问题的求解, 进而提出一种求解非线性参数反演问题的大范围收敛(HomotoyItakura SaitoRegularization, HISR) 方法.为保证迭代稳定性, 并同时削弱观测噪声的影响, 同伦参数的修正采用了连续化修正方法.本文将HISR方法应用于求解带有平衡及非平衡吸附效应的一维非饱和土中溶质迁移参数反演问题, 计算结果表明HISR方法具有大范围收敛性及计算稳健性, 同时有较强的抵抗观测噪声的能力. 相似文献
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铜离子在非饱和土中迁移的离心模型试验研究 总被引:1,自引:0,他引:1
利用土工离心机考察了铜离子泄漏后6个月至3年的时间里非饱和土中铜离子的变化和污染物的迁移机理。通过4种黏性上的离心模型试验研究,总结出铜离子在这类土体中的扩散规律。铜离子在一年内,主要受重力影响和水力梯度的作用,随渗流运移,存在一个舌状竖向扩散峰,污染范围近似呈三角形;一年后扩散范围逐渐转变为近似的正方形。竖向扩散速度高于水半向。土体密实度对铜离予的扩散有较为明显的影响,有效的击实或者碾压有助下防止污染物迁移。黏粒含量对铜离子的迁移阻碍非常迅速而且有效,黏粒含量很小的变化都会对迁移范围和速度有较大的影响。 相似文献
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在干旱半干旱地区由于土体蒸发速率大而引发的盐渍化会对相关区域范围内的工程构筑物耐久性构成潜在威胁。因此,准确预测土体孔隙相对湿度对于指导工程构筑物防盐具有重要意义。基于土体孔隙水化学势与孔隙气体始终处于平衡状态这一结论,根据化学平衡原理推导了土体孔隙相对湿度计算式。通过与测得的盐溶液空气相对湿度进行对比,结果表明:不同温度不同浓度下的相对湿度计算值与试验值吻合程度高,并且优于R&S计算模型,尤其在溶液中溶质浓度处于近饱和状态时其吻合效果更为明显。同时,在不改变计算参数的前提下,将计算得到的孔隙相对湿度表达式代入到已有数值模型中,经比较发现:计算结果与试验结果吻合程度高,尤其在蒸发速率和体积含水量的预测上。综上所述,新提出的非饱和盐渍土孔隙相对湿度计算式在水盐迁移计算过程中是有效的。 相似文献
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非饱和土热力学参数确定的探讨 总被引:2,自引:1,他引:1
研究非饱和土热力学的力学性质,必须建立能量守恒方程,表征能量的两个基本物理力学参数(体积比热系数和热传导系数)的确定是求解能量守恒方程的重要因素。对于不同颗粒组成的土体,对其干燥颗粒有效热力学参数进行了分析,对固体、液体和气体三相共存的热力学参数进行了研究,并对计算结果进行了对比分析,在此基础上,提出了较适合计算热传导系数的方法,并将此方法和体积平均法、自洽法及Hashin-Strikman方法进行了比较。经与试验结果对比表明:提出的方法能较好地描述非饱和土的热力学参数特性。 相似文献
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非饱和土应力状态是采用有效应力( –ua)和基质吸力(ua–uw)作为应力状态变量,相应的Mohr-Coulomb破坏包面是在有效应力、基质吸力和剪应力的三维坐标系中的曲面(通常在应用中假定为平面)。根据应变等效性原理定义损伤变量,由非饱和土给出损伤变量与偏应力的曲线,并得到非饱和土的损伤阈值与基质吸力呈指数函数关系。采用一非饱和土土坡开挖过程的算例,说明基于损伤演化描述的稳定性数值分析方法可行。 相似文献
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A discrete model for unsaturated granular soils has been developed. Three discrete entities have been defined: particles, water menisci and pores. Local interaction forces and water transfer mechanisms have been integrated into a model through the appropriate equilibrium and balance equations. The results of several numerical tests using this model have been described and discussed. Simulations include wetting and drying under load tests, the application of suction cycles and the effect of a deviatoric stress ratio on wetting‐induced collapse. The model reacts just as true granular soil samples behave in laboratory tests. The model provides a new insight into the internal mechanisms leading to large‐scale features of behaviour such as wetting‐induced collapse or the increase in soil strength provided by suction. The paper also stresses that matric suction changes acting on a granular structure are capable of explaining most of the macroscopic features of stress–strain behaviour. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
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The paper describes and evaluates an incremental plasticity constitutive model for unsaturated, anisotropic, nonexpansive soils (CMUA). It is based on the modified Cam-Clay (MCC) model for saturated soils and enhances it by introducing anisotropy (via rotation of the MCC yield surface) and an unsaturated compressibility framework describing a double dependence of compressibility on suction and on the degree of saturation of macroporosity. As the anisotropic and unsaturated features can be activated independently, the model is downwards compatible with the MCC model. The CMUA model can simulate effectively: the dependence of compressibility on the level of developed anisotropy, uniqueness of critical state independent of the initial anisotropy, an evolving compressibility during constant suction compression, and a maximum of collapse. The model uses Bishop's average skeleton stress as its first constitutive variable, favouring its numerical implementation in commercial numerical analysis codes (eg, finite element codes) and a unified treatment of saturated and unsaturated material states. 相似文献
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In this research, the interfacial energy is taken into account in the deformation work for unsaturated soils. Based on porous media theory, the thermodynamic balance equations for each phase and the interface are used to derive the work input for unsaturated soils. The work input equation serves as the basis and starting point for the choice of stress state variables, based on which the conjugate stresses and strain increments are derived. The influences of the interfaces on the effective stress and the constitutive law for the liquid phase are then discussed based on the work input equation. The effective stress can be expressed as Bishop's type, and the effective stress parameter is shown to be a function of both the degree of saturation and the interfacial area. The constitutive law for the liquid phase under dynamic condition is also presented. The relationship among interfacial area, saturation, and capillary pressure is proposed to calculate the value of the effective stress. Experimental data obtained from literature are used to validate the proposed model equations. Results show that our findings are in accordance with the existing research. Unlike the phenomenal study, our research has a rigorous theoretical basis, which lays a foundation for further research of unsaturated soils considering the interfacial effects. 相似文献
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Eduardo Rojas Jaime Horta María L. Pérez-Rea Christian E. Hernández 《国际地质力学数值与分析法杂志》2019,43(6):1143-1161
Different phenomena influence the strength and volumetric behavior of unsaturated soils. Among the most important are suction hardening, hydraulic hysteresis, and the influence of volumetric strain on the soil-water retention curves. Fully coupled hydro-mechanical models require including all three phenomena in their constitutive relationships. Among these phenomena, suction hardening is the most influencing as it determines the apparent preconsolidation stress, the position of the loading-collapse yield surface, and the shift of both the isotropic consolidation and the critical state lines. In this paper, a fully coupled hydro mechanical model is presented. It is based on the modified Cam-Clay model but includes a yield surface with anisotropic hardening that takes account of the shift of the critical state line with suction. For highly overconsolidated materials, the sub-loading surface concept has been included in order to increase the precision of the model for these materials. The shift of the retention curves produced by volumetric strains is simulated using a hydraulic model based on the grain and current pore size distribution of the soil. 相似文献
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非饱和土水-力本构模型及其隐式积分算法 总被引:1,自引:0,他引:1
在已有工作基础上建立了水力-力学耦合的非饱和土本构模型,在硬化方程中考虑饱和度的影响,同时在土水特征曲线中考虑了塑性体变的影响,从而使模型可以反映非饱和土中的毛细现象与土中弹塑性变形现象的耦合行为。采用隐式积分方法,建立了非饱和土耦合模型的数值模型,并推导了得到了水力-力学耦合的非饱和土的一致切线模量。利用该算法编制了本构模型计算的子程序,使其能向外输出切线刚度矩阵,用于有限元计算。为了验证该算法和程序的正确性,用所编制程序对不同路径下的土体行为进行了预测。通过预测结果与试验结果相对比,表明程序预测结果与试验数据相吻合,模型可以较好地模拟土体的水力-力学耦合行为特性。 相似文献
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A new constitutive model is developed for the mechanical behaviour of unsaturated soils based on the theory of hypoplasticity and the effective stress principle. The governing constitutive relations are presented and their application is demonstrated using several experimental data from the literature. Attention is given to the stiffening effect of suction on the mechanical response of unsaturated soils and the phenomenon of wetting‐induced collapse. All model parameters have direct physical interpretation, procedures for their quantification from test data are highlighted. Quantitative predictions of the model are presented for wetting, drying and constant suction tests. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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A comprehensive framework to define the constitutive behaviour of unsaturated soils is developed within the theory of mixtures applied to three‐phase porous media. Each of the three phases is endowed with its own strain and stress. Elastic and elastic–plastic constitutive equations are developed. Particular emphasis is laid on the interactions between the phases both in the elastic and plastic regimes. Nevertheless, the clear structure of the constitutive equations requires a minimal number of material parameters. Their identification is provided: in particular, it incorporates directly the soil–water characteristic curve. Crucial to the formulation is an appropriate definition of the effective stress. The coupled influence of this effective stress and of suction makes it possible to describe qualitatively many of the characteristic features observed in experiments, e.g. for normally consolidated soils, a plastic behaviour up to air entry followed by an elastic behaviour at increasing suctions, and, on the way back, an elastic behaviour, unless compression is applied in which case plastic collapse occurs. Copyright © 2000 John Wiley & Sons, Ltd. 相似文献