粘土矿物含量对崩岗土体抗剪强度的影响

发布时间：2018-01-03 05:38

本文关键词：粘土矿物含量对崩岗土体抗剪强度的影响　出处：《福建农林大学》2017年硕士论文　论文类型：学位论文

【摘要】：崩岗作为南方典型土壤侵蚀现象,研究其土壤抗剪强度有助于认识崩壁崩塌的作用机理,对崩岗治理具有现实意义。本研究选取福建省安溪县一处典型崩岗崩壁,根据土壤特征将其划分为红土层、砂土层、碎屑层作为研究对象,通过外源添加高岭土重置粘土矿物含量梯度以及设置不同含水率梯度,采用扫描电镜及室内直接剪切试验,观察土壤微观结构,同时从宏观层面探讨不同含水率条件下粘土矿物含量梯度对崩岗各土层重塑土抗剪特性的影响。结果表明:(1)通过扫描电镜观察各土层土壤颗粒在不同粘土矿物含量梯度下的微观形态,探讨重塑土粘聚力与内摩擦角的变化规律。呈负电荷的粘土矿物可嵌入土壤中针状氧化铁团簇结构,形成胶结作用强化土壤的加固粘聚力;粘土矿物对土壤颗粒的镶嵌及黏附作用使其形成较为稳固的团聚结构,可在某种程度抵御外界作用对土体产生的剪切破坏。微观观察粘土矿物嵌入土壤颗粒的形态及高含量梯度下粘土矿物对土壤颗粒的覆盖情状,可佐证室内直剪试验。(2)模拟自然条件,设置含水率20%条件下,崩岗红土层土壤抗剪强度随粘土矿物含量增加呈现增大趋势,但不同梯度下抗剪强度增幅存在差异。梯度10:1时,红土层土壤抗剪强度呈现骤增趋势,进一步提高粘土矿物含量则增幅趋于平缓;砂土层同红土层相似,其抗剪强度随粘土矿物含量梯度增加随之增大,且在梯度10:1处大幅增长,但砂土层各粘土含量梯度抗剪强度增长幅度与红土层相较则略小;含水率20%条件下的崩岗碎屑层土壤抗剪强度亦随粘土矿物含量梯度增加呈现逐渐增大的趋势,但其增幅较为均匀,并未在某一具体梯度下呈现骤增态势。粘土矿物对崩岗土壤粘聚力及内摩擦角的影响共同表征其抗剪强度,二者随粘土矿物含量梯度增加而主要呈现增强趋势,但二者影响程度受土壤本身性质所局限,同一梯度下不同土层抗剪强度变化强弱有所差异。(3)考虑强降雨汛期,提高含水率梯度至25%、30%,探讨其高含水率条件下不同粘土矿物含量梯度对崩岗三个土层抗剪强度的影响。同一含水率下,抗剪强度随粘土矿物含量增加而增强,比较同一粘矿含量梯度下不同含水率对其抗剪强度的影响,室内直剪试验所得结论为:含水率20%含水率25%含水率30%,含水率是影响崩岗各土层土体抗剪强度的主导因素,粘土矿物含量的添加对其影响抗剪强度有削弱作用。较高含水率条件下,崩岗各土层土壤抗剪强度呈现骤减趋势,随外源高岭土的添加,其下降幅度被不同程度控制,但不同土层的抑制程度对于其崩岗治理的现实意义各有不同体现。
[Abstract]:As a phenomenon of collapsing erosion in Typical Soils of southern China, the study on the shear strength of the soil is helpful to understand the mechanism of the collapse of the wall collapse, it has realistic significance to benggang governance. This study selected Anxi County of Fujian Province, a typical collapsing wall collapse, according to the characteristics of the soil can be divided into laterite layer, sand layer, elastic layer as the research object, by adding kaolin clay mineral content and the gradient reset set the gradient of different moisture content, using scanning electron microscopy and indoor direct shear test, observation of soil microstructure, and explore the different moisture gradient of clay mineral content under the condition of the soil influence benggang remolded soil shear characteristics from the macro level. The results showed that: (1) to observe the morphology of the soil particles in different gradient content of clay minerals under study by SEM. The variation law of remolded soil cohesion and internal friction angle is negative. The clay mineral bearing can be embedded in the soil of acicular iron oxide clusters, formation cementation of reinforced cohesive soil; inlay and adhesion effect of clay minerals on the soil particles to form agglomerate structure relatively stable, but in some way to resist external effects on soil shear damage. Covering the situation gradient microscopic observation of clay minerals embedded soil particle morphology and high content of clay minerals and soil particles, as evidenced by indoor direct shear test. (2) simulated natural conditions, set 20% conditions of moisture, collapsing clay layer soil shear strength increases with the increase of clay mineral content showed an increasing trend, but different gradient shear strength growth exists 10:1 gradient difference. When the clay layer shear strength of the soil has sharply increased, to further improve the content of clay minerals in gently; sand layer with laterite layer similar to the shear strength With the increase of clay mineral content gradient increases, and the gradient of 10:1 increased significantly, but the content of the clay sand layer gradient shear strength increase and the clay layer is smaller than the moisture content; collapsing debris layer shear strength of the soil with gradient of clay minerals content increased gradually increasing trend under the condition of 20%. But the increase is not uniform, showing a surge situation in a certain gradient. Clay minerals to collapse influential soil cohesion and internal friction angle of the common characterization of the shear strength, and the two main shows an increasing trend with the gradient of clay mineral content increased, but the impact of the two affected by the nature of soil limited and the same gradient under different soil shear strength change intensity difference. (3) considering the heavy rainfall in flood season, improve the moisture gradient to 25%, 30%, on the high gradient of moisture content of different clay mineral content conditions The effect of collapsing three soil shear strength. Under the same water content, the shear strength increases with the increase of clay mineral content increased, compared with a clay mineral content gradient under different influence of water content on shear strength of the indoor direct shear test results: 20% moisture content moisture content 25% 30%, water content is the dominant factor affecting the disintegration of each layer soil shear strength, adding the content of clay minerals on the influence weakens the shear strength. The conditions of high water cut, collapsing the soil shear strength has plummeted trend, with the addition of exogenous kaolin, the decrease of different degrees of control, but the degree of inhibition of different soil layers for the practical significance of collapsing management have different expression.

【学位授予单位】：福建农林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157.1

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