干湿循环下云南红土的剪切特性及土-水特性研究

发布时间：2018-05-08 06:47

本文选题：干湿循环 + 云南红土　；参考：《昆明理工大学》2017年硕士论文

【摘要】：本文针对云南地区红土愈发严重的干湿循环问题,以云南红土为研究对象,以干湿循环为控制条件,以不同影响因素下红土的宏微观特性为基础,结合理论分析,研究干湿循环条件下饱和红土的剪切特性、非饱和红土的土-水特性及土-水作用机理,对于有效解决红土地区日益严重的灾害问题具有重要意义。饱和红土的三轴剪切试验表明:随干湿循环次数和干湿循环幅度增加,饱和红土的应变软化现象增强,剪切峰值及其剪切破坏应变、黏聚力和内摩擦角、电导率都减小,初始变形模量、孔压峰值增大,微结构受损程度加深:结构变松散,红土颗粒破碎,孔隙变分散。随初始干密度增大,饱和红土的剪切峰值、初始变形模量、黏聚力和内摩擦角、电导率都增大,剪切破坏应变、孔压峰值减小,微结构受损程度减轻:结构变紧密,孔隙明显变小、变少。初始干密度对饱和红土剪切特性的影响最明显,干湿循环次数次之,干湿循环幅度的影响最小。随排水条件UU、CU、CD依次变化,饱和红土的应变软化现象越显著,剪切峰值、剪切破坏应变、初始变形模量、电导率都增大,黏聚力大小为:cuuccu≈ccd≈0,内摩擦角大小为:φcdφcuφuu≈0,有效黏聚力大小为:c'uuc'cu≈c'cd≈0,有效内摩擦角大小为:φ'cd≈φ'cuφ'uu≈0,孔压峰值大小为:uf,uuuf,cuuf,cd=0,微结构受损程度减轻:整体结构变密实,孔隙减少。非饱和红土的土-水特性试验表明:随初始干密度增大,红土的进气值增高,脱水及吸水斜率、残余含气量减小,残余含水量、电导率增大,微结构呈现出结构更密实、孔隙减少的特征。随初始含水率增大,红土的进气值降低,脱水斜率、电导率增加,微结构表面形态从粒状向板状转变,红土颗粒轮廓及孔隙边缘越模糊。随预固结压力增大,红土的进气值增高,脱水斜率减小,残余含水量、电导率增加,微结构受损程度减轻:结构越密实,微观界面越平整,红土颗粒排列越规则且轮廓越模糊。随粒径增加,饱和后红土的含水率增加,进气值降低,脱水及吸水斜率、残余含气量增加,残余含水量减小,电导率先增加后减小,微结构受损程度加深:微观界面越起伏不平,颗粒排列越不规则,孔隙越大且不均匀。干湿循环过程中存在滞后现象,粒径比干密度的影响更明显。初始干密度、预固结压力、粒径(d=0.5mm除外)不同时可统一采用幂函数作为云南红土的土-水特性拟合模型,初始含水率不同时采用线性函数。干湿循环下饱和红土与水的作用:包括脱湿过程中水的逃逸作用、红土颗粒的吸附作用、红土体的硬化作用及收缩作用和吸湿过程中水的楔入作用、润滑作用、软化作用及红土体的膨胀作用,干湿循环过程中上述作用不断加深加剧,严重损伤了红土体的微结构,红土导电能力也不断改变,最终改变了饱和红土的剪切特性。干湿循环下非饱和红土与水的作用除了与上述作用有关以外,还与毛细作用、气相的流动作用和扩散作用关系紧密,最终体现在基质吸力与含水率的变化关系中。
[Abstract]:This paper aims at the dry and wet circulation of red soil in Yunnan area. Taking Yunnan red soil as the research object, taking the dry and wet cycle as the control condition, based on the macro and micro characteristics of the red soil under different influence factors, the shear characteristics of the saturated laterite under dry and wet conditions, the soil water characteristics of unsaturated laterite and soil water are studied. The three axis shear test of saturated red soil shows that the strain softening phenomenon of saturated red soil increases with the increase of dry and wet cycle times and the amplitude of dry and wet cycle, the peak shear peak and the shear breaking strain, cohesive force and internal friction angle, and the conductivity decrease. When the initial deformation modulus, the peak value of pore pressure increases, the damage degree of the microstructure is deepened: the structure becomes loose, the red soil particles are broken and the pores are dispersed. With the increase of the initial dry density, the peak shear peak, the initial deformation modulus, the cohesive force and the internal friction angle, the conductivity all increase, the shear failure strain, the pore pressure peak decrease, and the damage degree of microstructures is reduced. The effect of the initial dry density on the shear characteristics of saturated laterite is the most obvious. The dry and wet cycle times are the most obvious, the dry and wet cycle is the least. The UU, CU and CD changes with the drainage conditions, the more significant the strain softening phenomenon of the saturated laterite, the shear peak value, the shear failure strain, the initial deformation modulus, the conductivity. The cohesion size is increased, the cohesive force size is: cuuccu CCD 0, the internal friction angle is: Phi CD Phi Cu UU 0, the effective cohesive force size is 0, the effective internal friction angle is 0, the effective internal friction angle is: [Phi]'cu phi'uu 0, the size of the pore pressure peak is: UF, uuuf, the pore decreases. Soil water characteristics test showed that with the increase of initial dry density, the intake value of the red soil increased, the dehydration and water absorption slope, the residual gas content decreased, the residual water content, the conductivity increased, the microstructure showed more dense structure, and the porosity decreased. With the increase of initial water content, the intake value of the red soil decreased, the slope of dehydration, the electrical conductivity increased, microjunction. With the increase of pre consolidation pressure, the intake value of the red soil increases, the slope of the dehydration decreases, the residual water and the electrical conductivity increase, and the damage degree of the microstructures decreases with the increase of preconsolidation pressure. The more dense the structure is, the more smooth the microstructure is, the more regular the arrangement of the laterite particles and the blur the contour. The water content of the red soil increased, the water content of the red soil increased, the intake value decreased, the dehydration and water absorption slope, the residual moisture content increased, the residual water content decreased, the electrical conductivity increased first and then decreased, and the damage degree of the microstructures was deepened: the more irregular the micro interface was, the more irregular the particle arrangement, the larger the pore and the unevenness. There was a lag in the dry and wet cycle. The effect of particle size is more obvious than dry density. Initial dry density, preconsolidation pressure, particle size (except d=0.5mm) can not simultaneously use power function as a fitting model of soil water characteristics of Yunnan red soil. The initial water content does not use linear function at the same time. The effect of saturated red soil and water under dry and wet cycle, including the escape effect of water during dehumidification process The adsorption of red soil particles, the hardening of the red soil and the wedge action of the red soil, the wedge action of the water, the lubrication, the softening and the swelling of the red soil during the process of moisture absorption, the effects of the red soil in the dry and wet cycle aggravated, and the microstructure of the red soil was seriously damaged, and the conductivity of the red soil was constantly changed, and finally the satiety was changed. The effect of unsaturated laterite and water under dry and wet cycle is closely related to capillary action, gas flow and diffusion, which is finally reflected in the change of matrix suction and water content in the action of unsaturated laterite and water under dry and wet cycle.

【学位授予单位】：昆明理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU446

【参考文献】