兰州黄土侧限松弛特性试验研究

预变形过程可以认为是应力历史的作用，为了探明预变形对兰州黄土应力松弛特性的影响，开展了一系列室内侧限松弛试验，研究了不同预变形量条件下黄土的应力松弛过程曲线。试验结果表明：预变形量愈大，起始松弛应力愈大，在试验历时内的应力松弛量也较大。根据松弛曲线特征，提出松弛程度的概念，试验发现，预变形量愈大，达到同一松弛程度所需时间较短；随应力松弛进一步发展，这种时间差别愈明显。从试验出发，探讨了松弛过程的阶段性，将全过程分为瞬时松弛阶段、衰减松弛阶段和稳定松弛阶段3个阶段。预变形选择恒变形速率加载过程，研究了不同变形速率对松弛过程的影响。在分析松弛试验数据基础上，获得了一种能够描述卸载过程的流变关系，并对其可靠性进行了验证

Uniaxial relaxation characteristics of Lanzhou loess

The pre-strain process can be considered to be the effect of stress history. To investigate the stress relaxation characteristics of Lanzhou loess, a series of laboratory stress relaxation tests under confined conditions are conducted. The relaxation curves of loess under different pre-strains are analyzed. The experimental results indicate that the initial relaxation stress increases with the growth of the magnitude of pre-strain, which ultimately leads to bigger instantaneous relaxation. According to the characteristics of relaxation curves, a new conception of relaxation degree (RD) is proposed. With the pre-strain gets bigger, the time to reach the same relaxation degree becomes shorter; and with the development of relaxation, this kind of difference tends to be more obvious. Based on the analysis of experimental data, the stages of relaxation are analyzed and the whole process can be divided into three stages, including instantaneous relaxation stage, attenuation relaxation stage and stable relaxation stage. The constant strain rate loading is chosen; and its influence on the relaxation process under different strain rates is analyzed. Based on the experimental results, a new rheological relation is obtained and its reliability is verified by the validation test.