本文關鍵詞：粘土礦物含量對崩崗土體抗剪強度的影響　出處：《福建農(nóng)林大學》2017年碩士論文　論文類型：學位論文

  更多相關文章： 崩崗土層 粘土礦物含量 含水率 抗剪強度

【摘要】：崩崗作為南方典型土壤侵蝕現(xiàn)象,研究其土壤抗剪強度有助于認識崩壁崩塌的作用機理,對崩崗治理具有現(xiàn)實意義。本研究選取福建省安溪縣一處典型崩崗崩壁,根據(jù)土壤特征將其劃分為紅土層、砂土層、碎屑層作為研究對象,通過外源添加高嶺土重置粘土礦物含量梯度以及設置不同含水率梯度,采用掃描電鏡及室內(nèi)直接剪切試驗,觀察土壤微觀結構,同時從宏觀層面探討不同含水率條件下粘土礦物含量梯度對崩崗各土層重塑土抗剪特性的影響。結果表明:(1)通過掃描電鏡觀察各土層土壤顆粒在不同粘土礦物含量梯度下的微觀形態(tài),探討重塑土粘聚力與內(nèi)摩擦角的變化規(guī)律。呈負電荷的粘土礦物可嵌入土壤中針狀氧化鐵團簇結構,形成膠結作用強化土壤的加固粘聚力;粘土礦物對土壤顆粒的鑲嵌及黏附作用使其形成較為穩(wěn)固的團聚結構,可在某種程度抵御外界作用對土體產(chǎn)生的剪切破壞。微觀觀察粘土礦物嵌入土壤顆粒的形態(tài)及高含量梯度下粘土礦物對土壤顆粒的覆蓋情狀,可佐證室內(nèi)直剪試驗。(2)模擬自然條件,設置含水率20%條件下,崩崗紅土層土壤抗剪強度隨粘土礦物含量增加呈現(xiàn)增大趨勢,但不同梯度下抗剪強度增幅存在差異。梯度10:1時,紅土層土壤抗剪強度呈現(xiàn)驟增趨勢,進一步提高粘土礦物含量則增幅趨于平緩;砂土層同紅土層相似,其抗剪強度隨粘土礦物含量梯度增加隨之增大,且在梯度10:1處大幅增長,但砂土層各粘土含量梯度抗剪強度增長幅度與紅土層相較則略小;含水率20%條件下的崩崗碎屑層土壤抗剪強度亦隨粘土礦物含量梯度增加呈現(xiàn)逐漸增大的趨勢,但其增幅較為均勻,并未在某一具體梯度下呈現(xiàn)驟增態(tài)勢。粘土礦物對崩崗土壤粘聚力及內(nèi)摩擦角的影響共同表征其抗剪強度,二者隨粘土礦物含量梯度增加而主要呈現(xiàn)增強趨勢,但二者影響程度受土壤本身性質(zhì)所局限,同一梯度下不同土層抗剪強度變化強弱有所差異。(3)考慮強降雨汛期,提高含水率梯度至25%、30%,探討其高含水率條件下不同粘土礦物含量梯度對崩崗三個土層抗剪強度的影響。同一含水率下,抗剪強度隨粘土礦物含量增加而增強,比較同一粘礦含量梯度下不同含水率對其抗剪強度的影響,室內(nèi)直剪試驗所得結論為:含水率20%含水率25%含水率30%,含水率是影響崩崗各土層土體抗剪強度的主導因素,粘土礦物含量的添加對其影響抗剪強度有削弱作用。較高含水率條件下,崩崗各土層土壤抗剪強度呈現(xiàn)驟減趨勢,隨外源高嶺土的添加,其下降幅度被不同程度控制,但不同土層的抑制程度對于其崩崗治理的現(xiàn)實意義各有不同體現(xiàn)。
[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.

【學位授予單位】：福建農(nóng)林大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S157.1

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