土石混合填料大型三轴剪切试验研究

(1.西安科技大学 建筑与土木工程学院,陕西 西安 710054; 2.南京水利科学研究院 岩土工程研究所,江苏 南京 210024)

土石混合料; 大型三轴剪切试验; 应力-应变关系; 剪胀性; 体变速率

Large-scale triaxial shear test of soil rock mixture
JING Hong-jun1,ZHANG Yan-qing1,GU Xing-wen2,LING Hua2

(1.College of Civil and Architectural Engineering,Xi'an University of Science and Technology,Xi'an 710054,China; 2.Department of Geotechnical Engineering,Nanjing Hydraulic Research Institute,Nanjing 210024,China)

soil-rock mixture; large-scale triaxial shear test; stress-strain relation; dilatancy; volumetric rate

DOI: 10.13800/j.cnki.xakjdxxb.2019.0213

备注

为研究土石混合填料在不同土石混合比情况下的力学响应,以国道316旬阳至安康二级公路改建工程中的填石高路堤工程为依托,利用大型三轴剪切试验仪,在4种不同围压条件下,分别对土石混合质量比为3:7和3:2的试样进行固结不排水剪切试验。发现当土石混合比为3:7时,在低围压(200 kPa)条件下,试样应力-应变曲线为应变硬化型,在高围压(400,600和800 kPa)条件下,试样应力-应变曲线在达到峰值应力后有所下降,表现为弱应变软化。在4种围压条件下,试样体应变均表现为随轴向应变先增大后减小,即试样先剪缩后剪胀,且表现为随着围压的增大,剪缩量不断增大,然后达到峰值,随后体应变减小,表现出剪胀趋势,且随着围压的增大,剪胀趋势减弱。当土石混合比为3:2时,在4种围压条件下,试样应力-应变曲线均表现为应变硬化,无明显的峰值强度。试样体应变均随轴向应变增大而增大,即试样一直表现为剪缩,且围压越大,剪缩趋势越明显,剪缩量越大。体变速率(dεv/dε1)能较好地反映试样变形特性和应力-应变特性。结果 表明:土石混合比的变化对土石混合料剪胀性影响很大,对应力-应变特性的影响主要体现在加载后期。

To study the mechanical response of embankment fillings under different soil-rock mixing ratios,based on the project of high rockfill embankment in the reconstruction project of the Xunyang-Ankang secondary road of the National Highway 316,large-scale triaxial consolidated undrained shear tests were carried out on samples with mass ratios of soil-rock mixing of 3:7 and 3:2 under four different confining pressures.It is pointed out that when the soil-rock mixing ratio is 3:7,the stress-strain curve shows strain hardening under low confining pressure(200 kPa),and under high confining pressure(400,600 and 800 kPa),the stress-strain curves decreases after reaching the peak stress,which is characterized by weak strain softening.Under four confining pressures,the volumetric strain first increases and then decreases with the axial strain,that is,the sample shearing shrinkage at first,then dilatancy later,and with the increase of confining pressure,the amount of shearing shrinkage increases continuously,then reaches the peak value,and afterwards the volumetric strain decreases,showing the dilatancy trend,which is weakened with the increase of confining pressure.When the soil-rock mixing ratio is 3:2,under four confining pressures,the stress-strain curves show strain hardening without obvious peak strength.The volumetric strain increases with the increase of axial strain,i.e.,the sample shows shearing shrinkage,and as the confining pressure increase,the shearing shrinkage trend becomes apparent and the amount of shearing shrinkage becomes greater.The volumetric rate could well reflect the deformation and stress-strain characteristics of the samples.The results indicate that the change of soil-rock mixing ratio has great influence on the dilatancy of soil-rock mixture,and the influence on stress-strain characteristics is mainly reflected in the later stage of loading.