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现在被广泛公认的由Fredlund提出的非饱和土力学的双参数理论,即净应力和吸力为非饱和土的应力状态变量,不能直接考虑吸力历史及其饱和度对非饱和土的应力-应变关系和强度的影响。非饱和土三轴试验结果表明,即使净应力和吸力相同的条件下,经过干-湿循环试样与未经过干-湿循环试样的应力比-应变关系和强度是不相同的。在其他条件相同时,经历过干-湿循环的试样比未经过干-湿循环试样的应力比-应变关系要高、强度大和体变小。经过干-湿循环试样的饱和度低而强度高,主要是由于经过先期较高的吸力,相当于受过较大的前期有效压力,使试样成为超固结土。更多不同吸力历史的对比试验有待于进一步研究,以便为非饱和土的水力-力学特性耦合弹塑性本构模型定量地表示上述非饱和土的性质提供基础性试验数据。
It is now widely accepted that the two-parameter theory of unsaturated soil mechanics proposed by Fredlund, that is, the net stress and suction are the stress state variables of unsaturated soils, can not directly consider the relationship between the suction history and its stress-strain relationship with unsaturated soil And the impact of strength. The results of triaxial tests on unsaturated soils show that the stress-strain relationship and the strength of dry-wetted samples are different from those of non-saturated-wetted samples under the same conditions of net stress and suction. When the other conditions are the same, the samples that have undergone the wet-dry cycle have higher stress-strain relations than the dry-wet cycles, and have higher strength and smaller body. After the dry - wet cycle samples with low saturation and high strength, mainly due to the early high suction, the equivalent of a larger pre-effective pressure to make the sample become over-consolidated soil. More comparative tests of different suction history have yet to be further studied in order to provide basic experimental data for quantitatively representing the properties of unsaturated soils mentioned above, which are coupled with the elasto-plastic constitutive model of unsaturated soil.