长期交通荷载下压实黄土的稳定性状态

Steady States of Compacted Loess under Long-term Traffic Loading

研究目的:长期交通荷载下路基土体稳定性状态的判定是对土体动力承载能力的宏观把控,是工程中评估路基长期服役能力时的重要参考。本文基于大量动三轴试验结果,综合压实黄土的弹、塑性应变发展规律界定长期交通荷载下压实黄土的稳定性状态(稳定、亚稳定和不稳定),讨论阻尼比、累积应变、累积应变发展速率随动应力的发展规律。研究结论:(1)累积塑性应变、累积塑性应变发展速率和阻尼比呈现出明显的分阶段特征,当试样进入亚稳定状态时阻尼比进入平台段;(2)阻尼比随累积应变发展速率的变化规律呈现明显的阶段特征,采用双参数变化规律作为试样稳定状态的判据更加客观和显著;(3)稳定性状态判别标准的混乱是造成测试结论通用性较差的主要原因;(4)本文工作有助于建立更加完善、统一的稳定性状态判别标准。

Research purposes: Estimation of the steady states of subgrade soil under long-term traffic loading is significant in evaluating the operate ability of subgrade. It is a kind of macroscopic judgment on the dynamic bearing capacity of soil. The steady states of compacted loess were demarcated after analyzing the elastic and plastic strain variations,which is from the results of large number of cyclic triaxial experiments. All the tests were classified into three steady states,i. e. stable,metastable and unstable. The variations of accumulated plastic strain,the development rate of accumulated strain and the damping ratio versus dynamic stress were discussed.Research conclusions:( 1) There are obvious stage characteristics of the variations of accumulated plastic strain,the development rate of accumulated strain and the damping ratio,and the damping ratio enters the platform section once the sample enters the metastable stage.( 2) The change law of damping ratio with development rate of accumulated strain points also performs obvious stage characteristic,and it is more objective and significant to use the two-parameter change law as the criterion of the steady states of samples.( 3) The main reason for the poor universality of the test results might be the confusion of the criterion for identifying the steady states.( 4) The present work is helpful for establishing more perfect and unified criterion of the steady states.