水泥改良黄土路基动力稳定性评价参数试验研究
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摘要
为满足高速铁路对路基工后沉降及长期动力稳定性的要求,并为黄土地区路基填料的选择提供参考,本文分别通过短时及疲劳动三轴实验对水泥改良黄土的动力稳定性评价参数(短时及疲劳动剪应变门槛)随水泥掺量、围压及固结比的变化进行了研究,并探讨了两者之间的量值关系,以期通过方便快速的短时动三轴实验得到疲劳动剪应变门槛。研究结果表明:短时条件下,竖向塑性应变随动应力的增加逐渐增加,最终呈现出脆性破坏的特点,而随水泥掺量、围压及固结比的增大逐渐减小;动模量Ed随动应力σd的增加呈现出先增大后减小的趋势,而与水泥掺量、围压及固结比的增长呈现正相关规律;随着水泥掺量、围压及固结比的增大水泥改良黄土短时及疲劳动剪应变门槛、动应力门槛均呈近似线性增加;同一条件下,水泥改良黄土的疲劳动剪应变门槛与短时动剪应变门槛的比值在0.29～0.34之间,随围压及固结比的增大变化较小。
There is a higher requirement of post-construction settlement and long-term dynamic stability for the high-speed railway subgrade.In order to satisfy this requirement and provide reference for the selection of subgrade fillers in loess areas,this paper uses the short-term and fatigue dynamic triaxial tests to examine the change in the dynamic stability evaluation parameters(short-term and fatigue dynamic shear strain threshold)(SDSST and FDSST) of the cement-improved loess with cement content(η),confining pressure(σ3) and consolidation ratio(Kc).The relationship between SDSST and FDSST is discussed,and it is expected to obtain the fatigue dynamic shear strain threshold by the convenient and rapid short-time dynamic triaxial experiment.The results show that(1) under the short time conditions,the vertical plastic strain increases with the increasing dynamic stress,and finally presents the characteristics of brittle failure,while gradually decreases with the increase of η,σ3 and Kc.(2) The dynamic modulus Edincreases first and then decreases with the increasing dynamic stress σd,while Edshows a positive correlation with the increase of η,σ3 and Kc.(3) The SDSST and FDSST,and the dynamic stress threshold linearly increase with the increase of η,σ3 and Kc.(4) Under the same condition,the ratio of FDSST to SDSST of the cement-improved loess ranges between0.29 and 0.34,which changes little with the increase of η,σ3 and Kc.
There is a higher requirement of post-construction settlement and long-term dynamic stability for the high-speed railway subgrade.In order to satisfy this requirement and provide reference for the selection of subgrade fillers in loess areas,this paper uses the short-term and fatigue dynamic triaxial tests to examine the change in the dynamic stability evaluation parameters(short-term and fatigue dynamic shear strain threshold)(SDSST and FDSST) of the cement-improved loess with cement content(η),confining pressure(σ3) and consolidation ratio(Kc).The relationship between SDSST and FDSST is discussed,and it is expected to obtain the fatigue dynamic shear strain threshold by the convenient and rapid short-time dynamic triaxial experiment.The results show that(1) under the short time conditions,the vertical plastic strain increases with the increasing dynamic stress,and finally presents the characteristics of brittle failure,while gradually decreases with the increase of η,σ3 and Kc.(2) The dynamic modulus Edincreases first and then decreases with the increasing dynamic stress σd,while Edshows a positive correlation with the increase of η,σ3 and Kc.(3) The SDSST and FDSST,and the dynamic stress threshold linearly increase with the increase of η,σ3 and Kc.(4) Under the same condition,the ratio of FDSST to SDSST of the cement-improved loess ranges between0.29 and 0.34,which changes little with the increase of η,σ3 and Kc.
引文
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[2]肖军华.循环荷载下路基压实粉土的临界应力与应变水平[J].水文地质工程地质,2010,37(5):61-66.[XIAO J H.The threshold stress and strain levels of compacted silt under repeated loadings[J].Hydrogeology&Engineering Geology,2010,37(5):61-66.(in Chinese)]
[3]张勇,孔令伟,郭爱国,等.循环荷载下饱和软黏土的累积塑性应变试验研究[J].岩土力学,2009,30(6):1542-1548.[ZHANG Y,KONG LW,GUO A G,et al.Cumulative plastic strain of saturated soft clay under cyclic loading[J].Rock and Soil Mechanics,2009,30(6):1542-1548.(in Chinese)]
[4]梅慧浩,冷伍明,刘文劼,等.持续动荷载作用下基床粗粒土填料累积塑性应变试验研究[J].铁道学报,2017,39(2):119-126.[MEI H H,LENGW M,LIU W J,et al.Experimental study on accumulated plastic strain of coarse grained soil filling in subgrade bed under persistent dynamic loading[J].Journal of the China Railway Society,2017,39(2):119-126.(in Chinese)]
[5]段俊彪.水泥及石灰改良土填料动力特性实验分析[J].铁道勘察,2006(4):39-41.[DUAN J B.Experimental analysis on dynamics characteristics of cement and lime improved soil fillings[J].Railway Investigation and Surveying,2006(4):39-41.(in Chinese)]
[6]胡一峰,李怒放.高速铁路无砟轨道路基设计原理[M].北京:中国铁道出版社,2010.[HU Y F,LI NF.Theory of ballastless track-subgrade for high speed railway[M].Beijing:China Railway Publishing House,2010.(in Chinese)]
[7]Hu Y,Gartung E,Prühs H,et al.Bewertung der Dynamischen Stablitittvon Erdbauwerken unter Eisenba-hnverkehr[J].Geotechnik,2003,26(1):42-56.
[8]Hu Y,Huapt W,Müllner B.Res Col-Versuche zur Prüfung der Dynamischen Langzeist9bilitat von TA/TM-B9den unter Eisenbahnverkehr[J].Bautechnik,2004,81(4):295-306.
[9]VUCETIC M.Cyclic Threshold Shear Strains Soils[J].Geotechnical Engineering,1994,120(12):2208-2228.
[10]T L Youd.Compaction of Sands by Repeated Shear Straining[J].Journal of Soil Mechanics&Foundations,1972,98(7):709-725.
[11]Silver M L,Seed H B.Volume Changes in Sands during Cyclic Loading[J].Soil Mechanics&Foundations,1991,97:1171-1182.
[12]刘晓红.高速铁路无砟轨道红黏土路基动力稳定性研究[D].长沙:中南大学,2011.[LIU X H.Research on dynamic stability of red clay subgrade under ballastless track of high-speed railway[D].Changsha:Central South University,2011.(in Chinese)]
[13]刘晓红,杨果林,方薇.武广高铁无碴轨道路堑基床长期动力稳定性评价[J].中南大学学报(自然科学版),2011,42(5):1393-1398.[LIU X H,YANG G L,FANG W.Long-term dynamic stability evaluation of cutting bed under ballastless track of Wuhan-Guangzhou high-speed railway[J].Journal of Central South University(Science and Technology),2011,42(5):1393-1398.(in Chinese)]
[14]谢琦峰,刘干斌,范思婷,等.循环荷载下饱和重塑黏质粉土的动力特性研究[J].水文地质工程地质,2017,44(1):78-83.[XIE Q F,LIU G B,FAN S T,et al.A study of dynamic characteristics of the saturated remolded clayey silt under circle load[J].Hydrogeolog&Engineering Geology,2017,44(1):78-83.(in Chinese)]
[15]刘建坤.路基工程[M].北京:中国建筑工业出版社,2006.[LIU J K.Subgrade Engineering[M].Beijing:China Architecture&Building Press,2006.(in Chinese)]
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