三轴状态原状结构性黄土基质吸力特性研究  

Experimental study on matrix suction of undisturbed structural loess by triaxial test

作　　者：褚峰[1] 邵生俊[1] 陈存礼[1] 

机构地区：[1]西安理工大学岩土工程研究所,陕西西安710048

出　　处：《西北农林科技大学学报（自然科学版）》2015年第12期199-208,共10页Journal of Northwest A&F University(Natural Science Edition)

基　　金：国家自然科学基金项目(50878183)

摘　　要：【目的】研究三轴应力条件下原状结构性黄土的基质吸力特性,为黄土的工程应用提供参考。【方法】通过常规三轴试验,研究采自陕西西安、甘肃定西、新疆石河子的黄土1、黄土2和黄土3 3种原状结构性黄土的构度指标,分析构度指标随含水率的变化关系及基质吸力随构度指标的变化关系。在不同湿度、不同围压条件下,通过非饱和土三轴仪对原状结构性黄土进行控制气压力的常含水率试验,分析饱和度、围压对基质吸力的影响,并揭示常含水率剪切过程中基质吸力的变化规律。【结果】原状结构性黄土的基质吸力和构度指标均随含水率的增大而降低,基质吸力随构度指标的升高而增大,表明黄土的结构性越强,基质吸力相对越大;在固结过程中,试样基质吸力随着围压的增大而逐渐降低;在试样剪切过程中,不同含水率试样基质吸力随轴向应变的增长表现出不同的变化规律,3种供试黄土含水率(w)小于塑限含水率(即黄土1w=13%,15%,黄土2w=15%,18%,黄土3w=11%,13%)时,试样基质吸力随着轴向应变的增加而增大,当含水率大于等于塑限含水率(即黄土1w=18%,23%,黄土2w=21%,24%,黄土3w=16%,20%)时,试样基质吸力随着轴向应变的增加而减小。在初始含水率引起的饱和度变化及试样剪切过程中引起的饱和度变化两种情况下,试样的基质吸力有着不同的变化规律,前者呈单调下降趋势,后者在含水率小于塑限时呈单调上升趋势,在含水率大于等于塑限时呈单调下降趋势。【结论】结构性黄土基质吸力特性与湿度、构度、围压、饱和度等多种因素相关;土样含水率在大于等于塑限与小于塑限时基质吸力有着不同的变化趋势。【Objective】Matrix suction of undisturbed structural loess was studied by triaxial test to provide guidance for the practical engineering application.【Method】By triaxial test,the structural index of undisturbed structural loess from Xi＇an Shaanxi①,Dingxi Gansu ②,and Shihezi Xinjiang ③ was investigated.Change of the structural index with moisture content was analyzed and the relationship between matric suction change and the structural index was determined.With different humilities and confining pressures and constant water content,the undisturbed structural loess was analyzed by unsaturated soil triaxial test.Then the effect of saturation degree and confining pressure on matrix suction was determined to reveal the variation of matrix suction in shear process.【Result】Matrix suction and structural index of undisturbed structural loess decreased with the increase of water content,and matrix suction of undisturbedstructural loess increased with the increase of structural index.In the consolidation process,matrix suction decreased with the increase of confining pressure.In the shear process,the suction changed differently with the increase of axial strain.When the water contents（w）（loess① w=13%,15%,loess②w=15%,18%,loess③w=11%,13%）were less than plastic limit,the matrix suction increased with the increase of axial strain,while when the water contents（loess①w=18%,23%,loess②w=21%,24%,loess③w=16%,20%）were larger than plastic limit,the matrix suction decreased with the increase of axial strain.At the saturation degrees caused by initial water content and shear process,the matrix suction changed differently.The former had a monotone decreasing trend.For the later,the trend was monotone increasing when the water content is less than plastic limit and it changed to monotone decreasing when the water content was larger than plastic limit.【Conclusion】The matrix suction characteristics of structural loess related to moisture,structural index,confining pressure,and saturation degree.

关 键 词：原状黄土 黄土结构性 构度 基质吸力 三轴剪切试验 

分 类 号：TU411[建筑科学—岩土工程]