摘要
本文以兰州黄土为研究对象,开展了不同加载速率条件下的K0压缩试验,并结合试验结果和“等速线理论”研究了震动荷载作用下黄土的动力学响应及其影响因素。研究结果显示,随着加载速率的升高,回弹系数(a)、塑性压缩系数(b)、前期固结压力(σp)以及内变量参考时间(τp)均会产生显著变化。其中,加载速率的升高对内变量参考时间影响最为剧烈,而加载速率对黏塑性应变速率参数(c)的影响可以忽略。通过对比震动荷载作用下土体应变发展的计算和实测结果表明,基于加载速率较快的试验结果获取的模型参数,其理论预测精度较高。在计算动力学问题中,σp的量值较静力条件下获取的参数要小2~3个数量级,这是使用该模型计算动力问题与静力问题的最大不同。进一步的计算分析表明,震动荷载作用下的动应变幅值与回弹系数正相关,而(b-a)/c和应力比(震动荷载的平均值与前期固结压力之比)正比于动荷载初期作用下发生的塑性应变(“残余应变”)。因而,在评价土体动荷载作用下的“残余应变”时,应综合考虑各力学参数和应力状态的影响。
In this paper,the Lanzhou loess is used as the research object,and the K 0 compression test under different loading rates is carried out.Combined with the experimental results and the“isokinetic theory”,the dynamic response of loess under vibration load and its influencing factors are studied.The results show that the spring back coefficient(a),plastic compression coefficient(b),pre-consolidation pressure(σp)and internal variable reference time(τp)change significantly with the increasing loading rate.Among them,the increase in loading rate has the most important effect on the internal variable reference time,and the effect of loading rate on viscoplastic strain rate parameter(c)is negligible.The calculation and experimental results of soil strain development under the action of contrast vibration show that the model parameters obtained by the test results with faster loading rate have higher theoretical prediction accuracy.In the computational dynamics problem,the value of theσp is 2-3 orders of magnitude less than that under the static conditions,which is used to calculate the maximum difference between the dynamic problem and the static problem.Further calculation and analysis show that the dynamic strain amplitude under the vibration load is positively correlated with the spring back coefficient,and the ratio(b-a)/c and the stress ratio(the ratio of the average of the vibration load to the pre-consolidation pressure)is proportional to the initial load under the action of the plastic strain(“residual strain”).Therefore,in the evaluation of soil dynamic load under the“residual strain”,the mechanical parameters and stress state of the impact should be taken into account.
作者
王文丽
王兰民
WANG Wenli;WANG Lanmin(Lanzhou Institute of Seismology,CEA,Lanzhou,Gansu730000 China)
出处
《水文地质工程地质》
CAS
CSCD
北大核心
2019年第5期113-119,共7页
Hydrogeology & Engineering Geology
基金
中国地震局地震预测研究所基本科研业务费项目资助(20151ESLE03)
国家自然科学基金项目资助(41671061
51478444)
