黄泛区粉土水力特征参数研究

发布时间：2018-04-22 19:50

本文选题：黄泛区 + 粉土　；参考：《中国地质大学》2017年博士论文

【摘要】：在黄泛区,粉土粒径较为均一的粉粒堆积孔隙缺乏细粒填充,即使按照现行规范的压实方法也不易形成密实结构体,毛细孔隙发达,雨季集中降水以及高地下水位有利条件下孔隙内水分运输致使路基土显著增湿、诱发多种工程问题出现。路基土的增湿机制涉及到(非)饱和渗透、水分特征曲线与毛细吸水等水力特征参数,而目前研究人员对黄泛区粉土的研究大都集中在压实度、毛细水上升高度及强度与含水量关系等方面,并没有注意到黄泛区粉土水力特征参数与干密度、压实含水量关系以及经验估算的方法。从已发表的研究文献看,目前还没有这方面的相关资料,这直接影响到对黄泛区粉土路基病害机理的认识与分析。鉴于此,本文从黄泛区粉土的水力特征参数入手,采用(非)饱和渗透系数、水分特征曲线、毛细吸水性室内实验与理论分析方法,研究黄泛区粉土的(非)饱和渗透性、毛细吸水性、水分特征曲线,获得了黄泛区粉土水力特征参数的变化规律,建立了土粒堆积填充等效孔隙模型,并将土粒堆积填充等效孔隙模型应用到水分特征曲线的估算方法中,阐明了黄泛区粉土水力特征参数随干密度与压实含水量的变化机理。本文的主要研究工作如下:1.通过资料搜集阐明了黄泛区的区域范围,涵盖了河南省郑州、开封、濮阳等地区,山东省菏泽(东明县)、济宁、聊城、济南、滨州、东营等地区,以及苏北故黄河泛滥地区。总体来说,该地区粉土的粉粒含量都在60%以上,粉土的砂粒绝大部分粒径均小于0.25mm;粘粒含量基本上处于5%~15%之间。Fredlund(F)模型适合描述黄泛区粉土粒径分布函数,模型参数回归表明:参数α大体上随着粉土砂粒含量的增大而增大;参数n的变化规律呈现分段性,当粉粒含量小于75%时,参数n随着粉粒含量的增大而降低,当粉粒含量大于75%时,参数n随着粉粒含量的增大而增大;参数m随着参数n的增大而减小,当参数n大于5.5以后,参数m基本稳定在0.5~1之间。2.通过简化堆积填充过程中土粒间互相作用关系与条件,构建了均一土粒堆积模式,推导了孔隙比(半径)与堆积土粒数,以及毛细管半径的函数关系表达式。紧密堆积状态下不存在细粒锲入效应,在此基础上推导出了依据粗粒细粒分量比的土粒堆积模式辨别方法,若细粒与粗粒径比处于0.05~0.5内时,均一堆积压实度为0.6,紧密堆积时所需细粒分量始终为0.325左右。按总孔隙体积相等的原则构建了两组份土粒堆积等效孔隙模式,并分别推导了粗粒与细粒骨架模式下孔隙比与等效毛细孔径的函数表达式。多组份土粒堆积涉及多种不等粒径颗粒之间接触堆积关系,采用了紧密堆积与两两组合的简化原则将多种不等粒径颗粒之间接触堆积关系简化为多种两组份土粒堆积关系,复杂孔隙构成关系也简化为骨架土粒孔隙、骨架-非骨架土粒孔隙和骨架-次骨架土粒孔隙。在此基础上,构建了多组份土粒堆积等效孔隙模式。最后,确立了多组份土粒堆积时的匹配原则与次序,等效孔隙参数的计算步骤与方法。3.在孔隙比位于0.51~0.71范围内,饱和渗透系数均值位于10-4cm/s左右,属于中等渗透性土。饱和渗透系数与孔隙比成指数关系,随孔隙比增大而非线性增大。压实含水量大于最优含水量时随孔隙比非线性增大最为显著,最优含水量时非线性最不显著。饱和渗透系数与压实含水量关系复杂。在大孔隙比的条件下,饱和渗透系数与压实含水量呈非线性关系,当压实含水量大于最优含水量时,饱和渗透系数随压实含水量的增大而增大,当含压实含水量小于最优含水量时,饱和渗透系数随含水量的增大而减小,最优含水量时,饱和渗透系数总是最小。在小孔隙比的条件下,试样的饱和渗透系数与压实含水量近似呈线性关系,饱和渗透系数随压实含水量的增大而减小。最优含水量条件下压实土体的饱和渗透系数对孔隙比的敏感度较低,也就是说,最优含水量条件下压实路基土时,实际控制孔隙比稍有偏差对饱和渗透系数造成的不利影响相对要小。4.黄泛区粉土的水分特征曲线具有典型水分特征曲线的形态特征,包含了边界效应区、第一过渡区和第二过渡区、非饱和残余区。(1)当压实含水量小于最优含水量时,干密度对水分特征曲线形态的影响在边界效应区;压实含水量大于最优含水量时,干密度对水分特征曲线形态的影响在过渡区。压实含水量控制着水分特征曲线过渡区的斜率与宽度。压实含水量高于最优含水量,过渡区曲线整体平缓,第一过渡区特征消失;压实含水量低于最优含水量,过渡区曲线有陡降段与平缓段,即第一过渡区和第二过渡区特征明显。(2)基于基质吸力0~500kPa范围内实验数据点,采用VG模型的拟合曲线与实验值比较吻合,且表达出水分特征曲线所具有典型形态特征。VG模型参数a、饱和含水率随干密度、压实含水量的增大而线性减小;残余含水率与干密度、压实含水量成线性关系,随着干密度增大而减小,随着压实含水量增大而增大;模型参数n由干密度与压实含水量共同控制。(3)基于AP模型的水分特征曲线预测值仅在0~100kPa的基质吸力范围内与实验值吻合度较好,当基质吸力大于100kPa时,预测含水量比实测值小的多。(4)采用基于土粒等效孔隙模型且叠加膜状水和吸附水后的水分特征曲线在基质吸力为0~500kPa范围内与实验数据更加吻合,能更准确地表达黄泛区粉土中、高饱和状态下的的水分特征曲线形态。但综合预测曲线并不完整,没有能反映包含高基质吸力段在内的水分特征曲线形态特征。5.毛细吸水量时程拟合曲线分为两类,毛细吸水过程有明显的快速吸水段和匀速吸水段之分,快速段内累计毛细吸水量与时间之间为二次函数关系,匀速吸水段内为两者为线性关系。毛细吸水过程吸水速度没有明显的陡降,整个毛细吸水过程中累计毛细吸水量与时间为二次函数关系。压实含水量控制着土样毛细吸水率-时间曲线的形态。压实含水量小于最优含水量时,土样吸水速率和吸水量均随着干密度的增大而减小,压实含水量大于最优含水量时,土样吸水速率和吸水量均随着干密度的增大而增大,最优含水量时,最大干密度土样的吸水速率和吸水量属于中等。干密度和压实含水量共同控制着土毛细吸水速率和吸水量,最优含水量和最大干密度状态附近毛细吸水现象比较显著。毛细吸水上升速度随着吸水时间延长逐渐减小,毛细水上升高度与吸水时间在双对数坐标中成二次函数关系;毛细水上升稳定后土的含水量沿吸水高度大致线性减小。6.总体上,非饱和排水量随着干密度的增大而减小,但是并非随着干密度的增加而单调减小或增大。干密度较小情况下,压实含水量为最优含水量时自重排水量最大;干密度较大情况下,压实含水量大于最优含水量时,土样在基质吸力大于25kPa后排水速度较大。压实含水量对排水时程曲线形态、排水速率影响较大。采用基于Arya-Paris模型的非饱和渗透系数计算结果表明,随着饱和度的降低,非饱和渗透系数迅速减小,当饱和度由0.9减小到0.1时,非饱和渗透系数快速从10-5数量级减小到10-10数量级,特别地,当基质吸力增加到105kPa时,非饱和渗透系数降低到10-10数量级,此时主要受粘粒控制,当基质吸力继续增大时,非饱和渗透系数的降低速率明显下降,且减小幅度也大大降低。
[Abstract]:In the yellow area, the fine particle size of silt particles is not filled with fine particles. Even if the compaction method of current standard is not easy to form dense structure, the capillary pores are well developed, the precipitation in the rainy season and the water level in the high ground water lead to the significant wetting of the subgrade soil, which induces a variety of engineering problems. The humidification mechanism of subgrade soil involves the hydraulic characteristic parameters such as (non) saturated permeability, water characteristic curve and capillary water absorption, but most researchers have concentrated on the compaction degree, the height of the capillary water and the relationship between the strength and the water content, and the hydraulic characteristic parameters and dry density of the yellow pan soil are not paid attention to. In view of the hydraulic characteristic parameters of the silty soil in the Yellow pan area, this paper starts with the hydraulic characteristic parameters of the silty soil in the Yellow pan region, and uses the saturated permeability coefficient and the moisture content. The (non) saturated permeability, capillary water absorption and water characteristic curves of the silt in the yellow area are studied, and the variation law of the hydraulic characteristic parameters of the silt is obtained. The equivalent Kong Ximo type of soil accumulation filling and filling is established, and the equivalent pore model is applied to the water to apply to the water. In the estimation of the characteristic curve, the variation mechanism of the hydraulic characteristic parameters of the silt in the Yellow River area with the dry density and the compacted water content is clarified. The main research work of this paper is as follows: 1. through the collection of data, the regional range of the Yellow River area is clarified, covering Zhengzhou, Kaifeng, Puyang, Shandong Province, Heze (Dongming county), Jining, Liaocheng, and other areas in Henan province. In Ji'nan, Binzhou, Dongying and so on, as well as the flooding area of the Yellow River in Northern Jiangsu Province, the silt content of the silt in this area is above 60% and the most of the silt grains are less than 0.25mm, and the.Fredlund (F) model of the clay content is basically between the 5%~15% and the grain size distribution function of the Yellow pan silt, and the regression of the model parameters shows that The parameter n increases with the increase of silt sand content, and the parameter n changes piecewise. When the powder content is less than 75%, the parameter n decreases with the increase of the powder content. When the powder content is more than 75%, the parameter n increases with the increase of the powder content; parameter m decreases with the increase of the parameter n, when the parameter n is greater than 5 After.5, the parameter m is basically stable between 0.5~1 and.2. by simplifying the intergranular interaction and condition of the soil particles in the process of packing and filling. A homogeneous soil accumulation model is constructed. The expression of the function relation between the pore ratio (radius) and the number of accumulated soil particles and the capillary radius is derived. On the basis of this, a method for identifying the soil grain accumulation based on the ratio of coarse grain and fine grain is derived. If the ratio of fine grain to coarse particle size is within 0.05~0.5, the bulk density is 0.6, and the fine grain components are always about 0.325. The equivalent pore pattern of two components is constructed according to the principle of total pore volume. The function expression of the pore ratio and the equivalent capillary pore size under the coarse grain and fine grain framework model is derived. The accumulation of multi component soil particles involves a variety of contact accumulation relations between different particle sizes, and the close accumulation and the 22 combination principle are adopted to simplify the contact accumulation relationship between different particle sizes into a variety of two components. The relationship between the complex pore structure and the complex pore structure is also simplified as the skeleton grain pore, the skeleton non skeleton pore and the skeleton and the skeleton grain pore. On this basis, the equivalent pore model of the multi component soil particle accumulation is constructed. Finally, the matching principle and order of the accumulation of multiple components of the soil are established, and the calculation procedure and method of the equivalent pore parameters,.3 When the pore ratio is located in the range of 0.51~0.71, the mean value of the saturation permeability coefficient is about 10-4cm/s, which belongs to medium permeability soil. The saturated permeability coefficient is exponentially related to the porosity ratio, and the nonlinearity increases with the increase of the pore ratio. When the compacted water content is larger than the optimal water content, it is the most significant with the non linear increase of the pore ratio, and the optimal water content is nonlinear. The saturation permeability coefficient has a complicated relationship with the compacted water content. Under the condition of large pore ratio, the saturated permeability coefficient and the compacted water content have a nonlinear relationship. When the compacted water content is greater than the optimal water content, the saturated permeability coefficient increases with the increase of the compacted water content. The saturation permeability coefficient is always the smallest when the water content is increased. Under the condition of small pore ratio, the saturated permeability coefficient of the sample is approximately linear with the compacted water content, and the saturated permeability coefficient decreases with the increase of the compacted water content. The saturated permeability coefficient of the compacted soil under the optimal water content condition The sensitivity of the pore ratio is low, that is to say, when the soil is compacted under the optimal water content, the actual control pore ratio is slightly deviated from the negative effect on the saturated permeability coefficient. The water characteristic curve of the.4. yellow pan silt has the shape characteristic of the typical water characteristic curve, including the boundary effect area and the first transition zone. And second transition zone, unsaturated residual area. (1) when the compacted water content is less than the optimal water content, the effect of dry density on the shape of water characteristic curve is in the boundary effect area; when the compacted water content is greater than the optimal water content, the influence of dry density on the shape of water characteristic curve is in the transition zone. The slope and width. The compacted water content is higher than the optimal water content, the transition zone curve is slow and the first transition zone is disappearing; the compacted water content is lower than the optimal water content, the curve of the transition region has a steep drop section and the gentle section, that is, the first transition zone and the second transition zone are distinct. (2) based on the experimental data points within the range of matrix suction 0~500kPa, V The fitting curves of the G model are in agreement with the experimental values, and the typical morphological characteristics of the water content curve are expressed as the.VG model parameter a. The saturated water content decreases linearly with the increase of dry density and compacted water content, and the residual water content is linearly related to dry density and compacted water content, and decreases with the increase of dry density, with the compaction water cut. The model parameter n is controlled by the dry density and the compacted water content. (3) the prediction value of the water characteristic curve based on the AP model is only in good agreement with the experimental values in the range of the matrix suction of 0~100kPa. When the matrix suction is greater than 100kPa, the predicted water content is much smaller than the measured value. (4) the equivalent pore model based on the soil particle is used. The water characteristic curve of superimposing membrane water and adsorbing water is more consistent with the experimental data in the range of matrix suction 0~500kPa, which can more accurately express the water characteristic curve in the high saturation state of the Yellow pan silt, but the comprehensive prediction curve is not complete and can not reflect the water characteristics including the high matrix suction section. The curve shape characteristic.5. capillary water absorption time course fitting curve is divided into two types, the capillary water absorption process has obvious quick water absorption section and uniform water absorption section, the accumulated capillary water absorption and time in the fast segment are two function relations, and the uniform water absorption section is linear relationship. The water absorption speed of the capillary water absorption process has no obvious steepness. The cumulative water absorption and time in the whole capillary water absorption are two functions. The compacted water content controls the shape of the soil sample capillary water absorption time curve. When the compacted water content is less than the optimal water content, the water absorption rate and water absorption of the soil sample decreases with the increase of dry density, and the compacted water content is greater than the optimal water content. The water absorption rate and water absorption increase with the increase of dry density. The water absorption rate and water absorption of the maximum dry density soil samples are medium. The dry density and the compacted water content control the soil capillary water absorption rate and water absorption, and the capillary water absorption near the optimal water content and the maximum dry density is remarkable. The rising velocity of capillary water absorbency gradually decreases with the extension of water absorption time, the rising height of capillary water and the time of water absorption are two function relations in the double logarithmic coordinates; the water content of the soil after the rising of capillary water is roughly linearly reduced along the water absorption height of.6., and the unsaturated drainage amount decreases with the increase of dry density, but not with the dry water. When the dry density is smaller, the weight of self weight and drainage is the largest when the compacted water content is the optimal water content. When the dry density is larger than the optimal water content, the soil sample has a larger drainage speed after the matrix suction is more than 25kPa. The results of the unsaturated permeability coefficient calculation based on the Arya-Paris model show that the unsaturated permeability coefficient decreases rapidly with the decrease of saturation, and when the saturation is reduced from 0.9 to 0.1, the unsaturated permeability coefficient decreases rapidly from 10-5 orders of magnitude to 10-10 orders of magnitude, especially when the matrix suction is increased to 105kPa, the unsaturated permeability coefficient is unsaturated. The permeability coefficient is reduced to 10-10 orders of magnitude, which is mainly controlled by the clay particles. When the matrix suction continues to increase, the reduction rate of the unsaturated permeability coefficient decreases obviously, and the decrease is also greatly reduced.

【学位授予单位】：中国地质大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：U416.1

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