非饱和压实黄土结构特性试验研究
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摘要
对增(减)湿到相同含水率及相同干密度的不同结构性非饱和压实黄土进行土-水特征曲线试验和三轴剪切试验,研究制样含水率引起的结构变化对非饱和压实黄土基质吸力、应力-应变特征及结构性参数的影响。研究结果表明:制样含水率引起的结构性对非饱和压实黄土的土-水特征曲线有明显的影响,小于塑限时基质吸力随制样含水率的增大而增大,最优制样含水率时非饱和压实黄土具有均匀小孔隙的团粒凝聚结构使其吸力相对最大;应力-应变曲线在最优结构状态时位于坐标最上端,小于最优制样含水率时的结构弱化程度相对较低,其应力-应变曲线逐渐下移,大于最优制样含水率时土样的结构弱化程度较高,其应力-应变曲线位于最下端;定义的结构性参数m?r能够合理反映压实黄土的结构性,弥补了压实土工程中用最优含水率和最大干密度指标无法反映土结构性影响的不足;屈服结构性参数m?r0能够合理反映出不同制样含水率压实黄土的结构弱化程度,结构弱化程度还反映在三轴剪切破坏强度上。
A series of soil water characteristic curve tests and triaxial shear tests were carried out on different structural unsaturated compacted loess samples after increasing or decreasing moisture to the same water content and dry density. The influence of different structures caused by the change of molding water content on matric suction and stress-strain characteristics as well as the structural parameter was investigated for the unsaturated compacted loess. The results indicate that the structure caused by the molding water content has a obvious effect on the soil water characteristic curve of unsaturated compacted loess. The matric suction increases with the increase of the molding water content when it is less than plastic limit. The compacted loess, which has the agglomerate structure with uniform pore size, results in relatively maximum suction at its best water content. The stress-strain curve of sample with optimum structure state is at the top of the coordinate. The degree of structural weakening is relative lighter when the water conent is less than the optimum molding water content, resulting in the stress-strain curve moves downward gradually. On contrarily, when the water conent is higher than the optimum molding water content, the degree of structural weakening is relative higher, which makes the stress-strain curve at the bottom. The proposed parameter m?r can reasonably reflect the structure of compacted loess, which overcomes the deficiency that the optimum moisture content and maximum dry density indexes cannot reflect the influence of soil structure in compacted soil engineering. The yield structural parameter m?r0 can reasonably reflect the degree of structural weakening of compacted loess with different molding water contents, and the degree of structural weakening is also reflected in the triaxial shear failure strength.
A series of soil water characteristic curve tests and triaxial shear tests were carried out on different structural unsaturated compacted loess samples after increasing or decreasing moisture to the same water content and dry density. The influence of different structures caused by the change of molding water content on matric suction and stress-strain characteristics as well as the structural parameter was investigated for the unsaturated compacted loess. The results indicate that the structure caused by the molding water content has a obvious effect on the soil water characteristic curve of unsaturated compacted loess. The matric suction increases with the increase of the molding water content when it is less than plastic limit. The compacted loess, which has the agglomerate structure with uniform pore size, results in relatively maximum suction at its best water content. The stress-strain curve of sample with optimum structure state is at the top of the coordinate. The degree of structural weakening is relative lighter when the water conent is less than the optimum molding water content, resulting in the stress-strain curve moves downward gradually. On contrarily, when the water conent is higher than the optimum molding water content, the degree of structural weakening is relative higher, which makes the stress-strain curve at the bottom. The proposed parameter m?r can reasonably reflect the structure of compacted loess, which overcomes the deficiency that the optimum moisture content and maximum dry density indexes cannot reflect the influence of soil structure in compacted soil engineering. The yield structural parameter m?r0 can reasonably reflect the degree of structural weakening of compacted loess with different molding water contents, and the degree of structural weakening is also reflected in the triaxial shear failure strength.
引文
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[15]汪东林,栾茂田,杨庆.重塑非饱和黏土的土-水特征曲线及其影响因素研究[J].岩土力学,2009,30(3):751-756.WANG Dong-lin,LUAN Mao-tian,YANG Qing.Experimental study of soil-water characteristic curve of remolded unsaturated clay[J].Rock and Soil Mechanics,2009,30(3):751-756.
[16]FREDLUND D G,XING ANQING.Equation for the soil-water characteristic curve[J].Canadian Geotechnical Journal,1994,31(4):521-532.
[2]谢定义,齐吉琳.土结构性参数及其定量化参数研究的新途径[J].岩土工程学报,1999,21(6):651-656.XIE Ding-yi,QI Ji-lin.Soil structure characteristics and new approach in research on its quantitative parameter[J].Chinese Journal of Geotechnical Engineering,1999,21(6):651-656.
[3]邵生俊,周飞飞,龙吉勇.原状黄土结构性及其定量化参数研究[J].岩土工程学报,2004,26(4):531-536.SHAO Sheng-jun,ZHOU Fei-fei,LONG Ji-yong.Structural properties of loess and its quantitative parameter[J].Chinese Journal of Geotechnical Engineering,2004,26(4):531-536.
[4]邵生俊,郑文,王正泓,等.黄土的构度指标及其确定方法[J].岩土力学,2010,31(1):15-19.SHAO Sheng-jun,ZHENG Wen,WANG Zheng-hong,et al.Structural index of loess and its testing method[J].Rock and Soil Mechanics,2010,31(1):15-19.
[5]陈存礼,胡再强,高鹏.原状黄土的结构性及其与变形特性关系研究[J].岩土力学,2006,27(11):1891-1896.CHEN Cun-li,HU Zai-qiang,GAO Peng.Research on relationship between structure and deformation property of intact loess[J].Rock and Soil Mechanics,2006,27(11):1891-1896.
[6]陈存礼,蒋雪,杨炯,等.结构性对压实黄土侧限压缩特性的影响[J].岩石力学与工程学报,2014,33(9):1939-1944.CHEN Cun-li,JIANG Xue,YANG Jiong,et al.The influence of structure on the confined compression characteristics of compacted loess[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(9):1939-1944.
[7]陈存礼,蒋雪,杨炯,等.结构性对压实黄土无侧限压缩特性的影响[J].岩石力学与工程学报,2014,33(12):2539-2545.CHEN Cun-li,JIANG Xue,YANG Jiong,et al.The influence of structure on unconfined compression characteristics of compacted loess[J].Chinese Journal of Rock Mechanics and Engineering,2014,33(12):2539-2545.
[8]SEED H B,CHAN C K.Structure and strength characteristics of compacted clays[J].Journal of Soil Mechanics and Foundation Engineering,1959,85(5):87-128.
[9]BARDEN L,SIDES G R.Engineering behaviour and structure of compacted clay[J].Journal of Soil Mechanics and Foundation Engineering,1970,96(4):1171-1201.
[10]GENS A.Constitutive modeling:application to compacted soils[C]//Proceedings of the 1st International Conference of Unsaturated Soils.Paris:[s.n.],1995:1179-1200.
[11]SIVAKUMAR V,WHEELER S J.Influence of compaction procedure on the mechanical behaviour of an unsaturated compacted clay.Part 1:wetting and isotropic compression[J].Geotechnique,2000,50(4):359-368.
[12]SIVAKUMAR V,TAN W C,MURRAY E J,et al.Wetting,drying and compression characteristics of compacted clay[J].Geotechnique,2006,56(1):57-62.
[13]VANAPALLI S K,FREDLUND D G,PUFAHL D E.The influence of soil structure and stress history on the soil-water characteristics of a compacted till[J].Geotechnique,1999,49(2):143-159.
[14]伊盼盼,牛圣宽,韦昌富.干密度和初始含水率对非饱和重塑粉土土水特征曲线的影响[J].水文地质工程地质,2012,39(1):42-46.YI Pan-pan,NIU Sheng-kuan,WEI Chang-fu.Effect of dry density and initial moisture content on soil-water characteristic curve of remolded unsaturated silt[J].Hydrogeology and Engineering Geology,2012,39(1):42-46.
[15]汪东林,栾茂田,杨庆.重塑非饱和黏土的土-水特征曲线及其影响因素研究[J].岩土力学,2009,30(3):751-756.WANG Dong-lin,LUAN Mao-tian,YANG Qing.Experimental study of soil-water characteristic curve of remolded unsaturated clay[J].Rock and Soil Mechanics,2009,30(3):751-756.
[16]FREDLUND D G,XING ANQING.Equation for the soil-water characteristic curve[J].Canadian Geotechnical Journal,1994,31(4):521-532.