An approach to rheometry in soil mechanics—Structural changes in bentonite, clayey and silty soils
An approach to rheometry in soil mechanics—Structural changes in bentonite, clayey and silty soils
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DOI：
10.1016/j.still.2006.01.007
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发表时间：
2006-12
影响因子：
6.5
通讯作者：
W. Markgraf;R. Horn;S. Peth
中科院分区：
文献类型：
--
作者：
W. Markgraf;R. Horn;S. Peth
流变学被认为是流动行为的科学，其中，基于等温方程，可以描述流体和塑性体受到外部应力的变形。胡克弹性定律、牛顿理想流体定律（粘度）、莫尔-库仑方程以及宾汉屈服是流变学领域中众所周知的关系和参数。流变仪是一种成熟的测量技术，用于确定流体和塑料体的特定流变特性。然而，这种技术在土力学调查中的应用还相对少见。为了解释点接触过程和强度，仍然缺少将这些结果外推到三轴、直剪或固结仪试验数据的方法。因此，本文的目的是介绍流变学作为一个合适的方法来确定土壤和矿物悬浮液的力学行为时，受到外部应力。为此，使用Na-膨润土Ibeco Seal-80（IS-80）作为测试材料，并且用不同浓度的NaCl溶液平衡悬浮液，以确定离子强度对颗粒间强度的影响和机械性能的变化。此外，变性土，粘土oxisol，无论是从巴西，和黄土材料从以色列，饱和NaCl在几个浓度进行了分析。使用平行板流变仪MCR 300（Modular Compact Rheometer，帕尔Physica，Ostfildern，德国）进行振荡试验。从应力-应变关系参数和特性参数中，分别确定和计算了触变性、储能模量G′和损耗模量G″、粘度η、屈服应力τ y和线性粘弹性变形（LVE）范围（包括极限值γ L）。在盐效应方面，振幅扫描试验表明，由于较高的NaCl浓度，富含CaCO 3的Avdat黄土的稳定性增加。在Avdat黄土和Ibeco Seal-80的对比试验中，可以说明湍流与滑动剪切行为。为了证明粘土矿物学的影响或纹理的影响粘土丰富的基板从巴西，蒙脱石变性土和高岭石oxisol进行了比较，表现出较高水平的存储弹性（稳定性）的情况下，蒙脱石和高岭石的值较低。振幅扫描试验的这些初步结果表明，流变仪是一种潜在的方法，调查矿物悬浮液和粘土或粉土的微观结构特性。
Rheology is regarded as the science of flow behaviour, where, based on isothermic equations, the deformation of fluids and plastic bodies subjected to external stresses may be described. Hooke's law of elasticity, Newton's law for ideal fluids (viscosity), Mohr-Coulomb's equation, and finally, Bingham's yielding are well known relationships and parameters in the field of rheology. Rheometry is a well established measurement technique to determine the specific rheological properties of fluid and plastic bodies. However, the application of this technique in soil mechanical investigations is yet relatively uncommon. In order to explain point contact processes and strength an extrapolation of such findings to data of triaxial, direct shear or oedometer tests is still missing. Thus, this paper aims to introduce rheometry as a suitable method to determine the mechanical behaviour of soils and mineral suspensions when subjected to external stresses. To do this a Na-bentonite, Ibeco Seal-80 (IS-80) has been used as a testing material, and the suspensions were equilibrated with NaCl solutions in different concentrations in order to determine the ionic strength effects on interparticle strength and changes in mechanical properties. Furthermore a vertisol, a clayey oxisol, both from Brazil, and loess material from Israel, saturated with NaCl in several concentrations were analysed. A parallel-plate-rheometer MCR 300 (Modular Compact Rheometer, Paar Physica, Ostfildern, Germany) has been used to conduct oscillatory tests. From the stress–strain relationship parameters and specific characteristics as thixotropy, storage modulus G′ and loss modulus G″, viscosity η, yield stress τyand the linear viscoelastic deformation (LVE) range including a limiting value γLwere determined and calculated, respectively. With aspect to salt effects, amplitude sweep tests on CaCO3rich Avdat loess show an increasing stability due to higher NaCl concentrations. In a comparative test of Avdat loess and Ibeco Seal-80, turbulent versus sliding shear behaviour could be illustrated. To demonstrate clay mineralogy effects or textural effects clay rich substrates from Brazil, a smectitic vertisol and a kaolinitic oxisol were compared, showing a higher level of stored elasticity (stability) in case of smectites and a lower value in regard to kaolinites. These preliminary results of amplitude sweep tests show that rheometry is a potential method of investigating microstructural characteristics of mineral suspensions and of clayey or silty soils.