青藏铁路沿线负温填土长期动力力学特性试验研究  

Experimental Study on Long-term Dynamic and Mechanical Properties of Negative Temperature Fill Along Qinghai—Tibet Railway

作　　者：董亮 姚昌瑞 田爽[2,3] 王柯 苏永华 DONG Liang;YAO Changrui;TIAN Shuang;WANG Ke;SU Yonghua(State Key Lab.for Track Technol.of High-Speed Railway,China Academy of Railway Sciences Corp.Ltd.,Beijing 100081,China;School of Civil Eng.,Harbin Inst.of Technol.,Harbin 150090,China;Heilongjiang Research Center for Rail Transit Eng.in Cold Regions,Harbin 150090,China)

机构地区：[1]中国铁道科学研究院集团有限公司铁道建筑研究所,北京100081 [2]哈尔滨工业大学土木工程学院,黑龙江哈尔滨150090 [3]黑龙江省寒区轨道交通工程技术研究中心,黑龙江哈尔滨150090

出　　处：《工程科学与技术》2023年第2期50-58,共9页Advanced Engineering Sciences

基　　金：中国铁道科学院集团有限公司基金项目(2020YJ037)。

摘　　要：为了评价冻土区路基的稳定性,本文对土体长期振动荷载下的动力特性进行研究,通过室内试验和理论分析相结合的手段对青藏铁路沿线填土的动力力学特性(动剪切模量和阻尼比)进行了分析。首先开展了室内固结不排水长期循环三轴试验,分析了不同负温、循环应力比对路基粉质黏土和地基砂土的动剪切模量和阻尼比等动力特性的影响。结果表明,路基粉质黏土的动剪切模量与温度呈现明显的负相关性,且随着循环应力比增大而呈现出较明显的增长趋势,阻尼比随着动剪切模量的增长而减小;地基砂土的动剪切模量和阻尼比受温度的影响与粉质黏土的响应规律呈现相同趋势,在温度为–10℃与循环应力比为0.2的相同条件下动剪切模量增至1.22倍,而阻尼比则减少到0.66倍。值得注意的是,砂土动剪切模量在循环应力比约为1时响应达到峰值,即动应力幅值达到围压时循环应力比增大,阻尼比增大而动剪切模量则呈现减小的趋势。随后在Wichtmann提出的高周循环模型基础上,建立了动剪切模量预测模型,能良好地反映动剪切模量在温度和循环应力比影响下,随振动次数变化的响应规律,通过拟合参数w0反映动剪切模量随循环应力比先增后减的规律,拟合数学关系显示长期振动次数约在13 000次或振动时长8 min以上时,土体的动力响应规律发生了明显变化。最后,基于Hardin-Drnevich双曲线模型对动剪切模量和阻尼比的试验结果进行拟合,得到了动剪切模量与阻尼比的函数关系式,从而能大致预测阻尼比随动剪切模量变化的趋势及范围,随着归一化剪切模量的增大阻尼比呈现出减小的趋势。In order to evaluate the stability of roadbed in frozen soil area, the dynamic shear modulus and damping ratio of fill along Qinghai—Tibet railway are analyzed by means of laboratory test and theoretical analysis. Firstly, the long-term consolidation undrained cyclic triaxial tests were carried out to analyze the effects of different negative temperature and cyclic stress ratio on dynamic shear modulus and damping ratio of subgrade silty clay and foundation sand. The results show that for subgrade silty clay, the dynamic shear modulus is negatively correlated with temperature, and increases with the increase of cyclic stress ratio, and the damping ratio decreases with the increase of dynamic shear modulus.For foundation sand, the dynamic shear modulus and damping ratio show the same trend under the influence of temperature as that of silty clay,but the value of dynamic shear modulus is about 110 MPa higher than that of damping ratio under the condition of –10 ℃ temperature and cyclic stress ratio of 0.2, which is 1.22 times, and the damping ratio is 0.66 times. It is worth noting that the dynamic shear modulus of sand responds to the peak value when the cyclic stress ratio is about 1, which means that when the dynamic stress amplitude reaches the confining pressure, the dynamic shear modulus tends to decrease while the damping ratio tends to increase with the increase of the cyclic stress ratio. Then, based on the high cycle model proposed by Wichtmann, the prediction model of dynamic shear modulus was established, which can well reflect the response law of dynamic shear modulus with vibration number under the influence of temperature and cyclic stress ratio. The fitting parameter w0reflects the law of dynamic shear modulus increasing first and then decreasing with cyclic stress ratio. The fitted mathematical relationship shows that the dynamic response law of soil changes significantly when the number of long-term vibrations is about 13 000 or the vibration duration is more than 8 minutes. Finally, based o

关 键 词：青藏铁路 负温动三轴试验 动力力学参数 循环应力比 高周循环预测经验模型 

分 类 号：TU435[建筑科学—岩土工程]