为描述非饱和土的应力-应变特性,基于非饱和土三轴剪切试验,提出泊松比变化率(即切线泊松比随轴向应变的变化速率)的概念,发现非饱和土的切线模量和泊松比变化率均随轴向应变的增加呈指数衰减规律,基于此提出了一种描述非饱和土应力-应变关系的新非线性模型。该模型不仅能描述应变硬化,而且能描述应变软化;能对非饱和土三轴不固结不排水剪、固结排水剪、固结不排水剪试验的应力-应变关系进行描述;模型共包含6个参数,物理意义明确,确定方法简便。利用提出的模型对国内外文献中的三轴试验进行了模拟,结果表明,模拟结果与试验数据有很好的吻合度,从而验证了模型对试验数据的合理性和适用性。 In order to describe the stress-strain characteristics of unsaturated soils, based on the triaxial shear tests of unsaturated soils, the conception of the rate of change of Poisson’s ratio (that is, the rate of change of tangent Poisson’s Ratio with axial strain) Modulus and Poisson’s ratio change exponentially with the increase of axial strain. Based on this, a new nonlinear model describing the stress-strain relationship of unsaturated soil is proposed. The model can not only describe strain hardening but also describe strain softening. It can describe the stress-strain relationship of unsaturated triaxial uncoupled undrained shear, consolidated drainage shear and consolidation undrained shear tests. The model contains 6 parameters, physical meaning is clear, determine the method is simple. The proposed model was used to simulate the triaxial tests in domestic and foreign literatures. The results show that the simulation results are in good agreement with the experimental data, which verifies the rationality and applicability of the model to the experimental data.