湖相软土单轴蠕变特性及其模型研究

Study on uniaxial creep characteristics and model of lacustrine soft soil

通过长期单轴蠕变试验,获得了湖相软土在不同应力水平下的应力-应变-时间的关系曲线,据此研究该软土的蠕变变形特性;在此基础上,利用非线性牛顿黏壶代替广义西原模型中的线性牛顿黏壶,将其从一维泛化到三维应力空间,建立了改进广义西原模型;利用曲线拟合法确定蠕变模型参数,并对该模型进行数值模拟验证。结果表明:软土在加载的瞬时均有一定的瞬时变形,然后随时间的延长,变形也明显增加;当应力水平低于50 kPa时,土体蠕变变形以衰减蠕变为主,处于黏弹性阶段;当应力水平高于50 kPa时,土体出现了衰减蠕变和稳定蠕变,呈塑性,并进入黏塑性阶段;由于环刀的侧限作用,软土土样未出现加速蠕变;改进广义西原模型具有非线性,由其计算所得的理论曲线能较好地与实测的蠕变试验曲线相吻合。

Through long-term uniaxial creep test,the stress-strain-time relation curve of lacustrine soft soil under different stress levels was obtained,and the creep deformation characteristics of the soft soil were studied.On this basis,the nonlinear Newton dashpot was used to replace the linear Newton dashpot in the generalized Nishihara model,and it was generalized from one-dimensional to three-dimensional stress space.The improved generalized Nishihara model was established,and the parameters of the rheological model were determined by curve fitting method,and the model was verified by numerical simulation.The results show that the soft soil has a certain instantaneous deformation at the moment of loading,and then the deformation increases obviously with the increase of time.When the stress level is lower than 50 kPa,the creep deformation is mainly attenuated creep,and the soil is in the viscoelastic stage;When the stress level is higher than 50 kPa,attenuated creep and stable creep occur,and the soil appears plasticity and enters the viscoplastic stage.There is no accelerated creep of the soft soil sample due to the lateral limiting effect of the ring cutter.The improved generalized Nishihara model is nonlinear,and the calculated theoretical curve is in good agreement with the measured creep test curve.