黄土的流变特性模拟与研究

Simulation and Study on Rheological Behavior of Loess

工程建筑活动与土体的应力、变形、强度具有紧密的相关性,使得对土体的变形、破坏规律的研究显得十分必要。在对某现场黄土土样剪切蠕变试验的基础上,本文以分数线性蠕变方程为理论模型,模拟了该土体的蠕变、强度和流变特性,得到了该土体的剪切模量G随时间t和随法向应力σn的变化规律。通过流变分析,得到了粘滞系数η对法向应力σn的变化率受剪应力τ影响的规律,即当剪应力值较小时,粘滞系数η随法向应力σn变化率较大,而当剪应力增大后,粘滞系数η随法向应力σn变化率变小。还得出了加载时间t对粘滞系数η随剪应力τ变化的影响规律,即每级加载一定时间后,粘滞系数η随剪应力τ变化规律,以及时间t对粘滞系数η变化率的影响。同时还从土的微观结构的角度进行了分析讨论。

Engineering construction activities have close coherence with stress、deformation、strength of soil mass, which makes the research on deformation and failure regularity necessary. The fraction-linearity creep equation was taken as the theoretical model in this paper. The creep、strength and rheological behavior of the soil mass were simulated, based on the results of shear creep tests of loess samples from a certain site. The relationship of shear modulus G of the soil mass with time t and normal stress σ_n were obtained. Through rheological analysis, the rules of effect of shear stress τ on the dependence between the ratio of change of viscosity coefficient η and normal stress σ_n are gained, that is, if the stress value is relatively small the ratio of change of viscosity coefficient η versus normal stress σ_n is relatively great and if the stress value is relatively great the ratio of change of viscosity coefficient η versus normal stress σ_n becomes relatively small. And the rules of effect of loading time t on viscosity coefficient η varying with shear stress τ are also gained ,which are the rule of viscosity coefficient η varying with shear stress τ and the influence of loading time t on the ratio of change of viscosity coefficient η during some certain time of each grade load. Discussions about these are presented from the viewpoint of the microstructure of soil.