磐安结构性黄土动阻尼特征及其演化规律研究

地震作用往往会导致结构性黄土动强度的衰减,引发黄土滑坡、振陷等一系列地质灾害,而强度的衰减与其阻尼特性密切相关,因而结构性黄土的动态阻尼特征及其演化规律问题是岩土工程抗震的重要研究课题之一。为此,以天水磐安结构性黄土为研究对象,开展了天然、饱和条件下原状黄土和重塑黄土的动力学特性试验。在试验基础上,分析并比较了黄土的动模量、动阻尼响应特征及其演化规律。研究表明:天然、饱和条件下原状黄土和重塑黄土的动应力随动应变的增大而增大,动模量随动应变的增大而减小,动阻尼比随着动应变的增大而增大;受黄土结构性的影响,原状黄土的最大动模量比重塑黄土的稍大,原状、重塑黄土的最大动模量比饱和原状、饱合重塑黄土的稍大;黄土结构性较强时需要考虑试样固结应力对阻尼比的影响,饱和重塑黄土可以忽略试样固结应力对阻尼比的影响。

DYNAMIC DAMPING CHARACTERISTICS AND EVOLUTION LAW OF PAN'AN STRUCTURAL LOESS

Seismic action often leads to the decay of dynamic strength of structural loess and a series of geological disasters such as loess landslide and depression, and attenuation of intensity is closely related to its damping characteristics, which makes dynamic damping characteristics of structural loess and its evolution law one of the important research topics of geotechnical engineering. In this article, the dynamic characteristics of undisturbed loess and remolded loess under natural and saturated conditions were studied. On the basis of experiments, the dynamic modulus, dynamic damping response characteristics and evolution law of loess are analyzed and compared. The results show that:(1) The dynamic stress of the original loess and remolded loess increases with the increase of the dynamic strain,while the dynamic modulus decreases with the increase of the dynamic strain, and the dynamic damping ratio increases with the increase of the dynamic strain; (2)Affected by structural properties of loess, the undisturbed loess is slightly larger than that of the remolded loess,and the maximum modulus of the undisturbed loess and remolded loess are slightly larger than that of saturated undisturbed loess and saturated remolded loess. The influence of the surrounding pressure on the damping ratio needs to be considered when the loess structure is strong, and the effect of the surrounding pressure on the damping ratio can be neglected by the saturated remolded loess.