氧化鐵膠體對崩崗?fù)馏w抗剪特性的影響
發(fā)布時間：2018-07-27 14:01
【摘要】：崩崗?fù)寥乐泻械挠坞x氧化鐵膠體是影響土體抗剪強(qiáng)度變化的因素之一,這是由于其與粘土礦物的交互作用使得土壤顆粒間具有一定的結(jié)構(gòu)強(qiáng)度。本文通過三軸剪切試驗(yàn)研究崩崗三個土層(紅土層、砂土層、碎屑層)的土體中含有不同量氧化鐵膠體時,各土層試樣的抗剪強(qiáng)度變化情況及發(fā)生這樣變化的原因。試驗(yàn)過程設(shè)置的四個氧化鐵含量梯度的試樣分別為空白試樣、去除1/3Fed試樣、去除2/3Fed試樣和完全去除Fed試樣,并從土體去除游離氧化鐵膠體前后理化性質(zhì)的改變、微觀電鏡掃描等方面分析引起土體抗剪強(qiáng)度的因素。經(jīng)過試驗(yàn)研究,主要結(jié)果如下:(1)經(jīng)過DCB法去除游離氧化鐵后,三個土層中的粘粒含量都出現(xiàn)明顯的增加,而大顆粒含量則有明顯的減少情況,其中紅土層變化最為明顯。這是由于DCB處理后,大顆粒吸附的氧化鐵與粘土礦物交互形成的團(tuán)聚體被破壞,將原先吸附在粗顆粒表面的粘粒釋放出來,成為粘粒的組成部分,使粘粒含量增加。(2)氧化鐵膠體的微觀膠結(jié)作用是土壤結(jié)構(gòu)強(qiáng)度的保證之一。由于針鐵礦與高嶺土之間生成了氫鍵和靜電引力,在SEM圖下,土壤中游離氧化鐵主要以"橋"或者"包膜"的形式與粘土礦物等顆粒之間形成聯(lián)結(jié)狀態(tài)并生成顆粒間引力,使之形成團(tuán)聚體顆粒。由于團(tuán)聚體會嵌入孔隙中,增大接觸面的滑動摩擦力,也使大孔隙被填成小孔隙,孔隙度減小,使結(jié)構(gòu)更加穩(wěn)定。而當(dāng)氧化鐵膠體被去除后,膠結(jié)氫鍵出現(xiàn)斷裂,導(dǎo)致氧化鐵膠體與粘土礦物的膠結(jié)氫鍵斷裂、顆粒間引力消失、聯(lián)結(jié)狀態(tài)被破壞,團(tuán)聚體結(jié)構(gòu)被破壞,結(jié)構(gòu)強(qiáng)度下降。(3)從總體上分析可以得出:試樣的抗剪強(qiáng)度為隨著含水率的增加而減小,而完全去除Fed試樣的抗剪強(qiáng)度卻是隨著含水率的增加,抗剪強(qiáng)度先增大后減小,說明了在不同含水率下,氧化鐵膠體可通過影響顆粒的形態(tài)特征、排列組合結(jié)構(gòu)、孔隙度等因素,使土壤的抗剪強(qiáng)度發(fā)生改變。而氧化鐵膠體主要是通過改變土體的粘聚力與內(nèi)摩擦角的大小而改變土壤的抗剪強(qiáng)度。在含水率一定時,三個土層試樣的粘聚力和內(nèi)摩擦角值隨試樣中含有去除氧化鐵膠體土樣比重的增大而呈減小的趨勢,但完全去除試樣中由于粘粒被完全的釋放,粘粒吸附水分能力增強(qiáng),毛細(xì)粘聚力增加,并且顆粒結(jié)構(gòu)一致孔隙度較小,易形成分子間的引力,使部分試樣在適宜的條件下粘聚力上升。(4)氧化鐵膠體與粘土礦物的膠結(jié)作用對崩崗?fù)馏w的結(jié)構(gòu)強(qiáng)度具有重大作用。由土體的偏應(yīng)力峰值變化情況表明:隨著試樣中氧化鐵膠體含量的減少,空白試樣、去除1/3Fed試樣、去除2/3Fed試樣、完全去除Fed試樣的抗剪強(qiáng)度值總體上呈下降的趨勢。但是下降趨勢并非都是逐漸下降,而是與游離氧化鐵膠體的發(fā)揮階段有關(guān),使其具有階段性和整體性的影響能力。另外,當(dāng)三個土層中游離氧化鐵被完全去除后,試樣的偏應(yīng)力都出現(xiàn)增大的現(xiàn)象。
[Abstract]:The free ferric oxide colloid contained in the toppling soil is one of the factors that influence the shear strength of the soil, which is due to the interaction between the soil and clay minerals, which makes the soil particles have a certain structural strength. In this paper, the shear strength of three soil layers (red soil layer, sand layer, clastic layer) is studied by triaxial shear test. When different amounts of ferric oxide colloid are found in the soil mass, the shear strength of each soil layer and the reason for the change are studied. The four samples with iron oxide content gradient were blank sample, 1/3Fed sample, 2/3Fed sample and Fed sample were removed, and the physical and chemical properties of free iron oxide colloid were changed before and after the removal of free iron oxide colloid. The factors that cause the shear strength of soil are analyzed by SEM. The main results are as follows: (1) after the removal of free iron oxide by DCB method, the clay content in the three soil layers increased obviously, while the large particle content decreased obviously, among which the clay layer changed most obviously. This is because after DCB treatment, the agglomerates formed by the interaction of iron oxide adsorbed by large particles with clay minerals are destroyed, and the clay particles previously adsorbed on the surface of coarse particles are released as part of the clay particles. The clay content was increased. (2) the microscopic cementation of ferric oxide colloid was one of the guarantee of soil structural strength. Due to the formation of hydrogen bonds and electrostatic force between goethite and kaolin, in SEM diagram, free iron oxide in the soil is mainly formed in the form of "bridge" or "coating" to form a connection state between clay minerals and other particles and form the gravitational force between them. To form agglomerate particles. Because the agglomeration experience is embedded in the pores and increases the sliding friction force of the contact surface, the macropores are filled into small pores, the porosity decreases, and the structure becomes more stable. However, when the iron oxide colloid is removed, the bonding hydrogen bond breaks, which leads to the breaking of the bonding hydrogen bond between the iron oxide colloid and the clay mineral, the disappearance of the gravitational force between the particles, the destruction of the bonding state, and the destruction of the structure of the aggregate. (3) from the overall analysis, it can be concluded that the shear strength of the specimen decreases with the increase of moisture content, while the shear strength of the sample with complete removal of Fed increases firstly and then decreases with the increase of moisture content. The results showed that the soil shear strength could be changed by influencing the morphology of the particles, the arrangement of the composite structure, the porosity and other factors under the different moisture content of ferric oxide colloid. The iron oxide colloid mainly changes the shear strength of soil by changing the cohesion of soil and the angle of internal friction. When the moisture content is constant, the cohesive force and the angle of internal friction of the three soil samples decrease with the increase of the specific gravity of the sample containing the removal of ferric oxide colloidal soil, but the complete removal of the sample is due to the complete release of the clay particles. The water adsorption ability of clay particles increases, the capillary cohesion increases, and the uniform porosity of particle structure is small, which makes it easy to form intermolecular gravity. The cohesion of some samples was increased under suitable conditions. (4) the cementation of ferric oxide colloid with clay minerals played an important role in the structural strength of the rockfall soil. The results show that with the decrease of the content of ferric oxide colloid in the sample, the shear strength of the blank sample, the 1/3Fed sample, the 2/3Fed sample, and the Fed sample is decreasing as a whole. However, the downward trend is not always decreasing gradually, but is related to the stage of free ferric oxide colloid, which makes it have the ability of stage and integrity. In addition, when the free iron oxide is removed completely in the three soil layers, the deflection stress of the sample increases.
【學(xué)位授予單位】：福建農(nóng)林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S157
本文編號：2148056
[Abstract]:The free ferric oxide colloid contained in the toppling soil is one of the factors that influence the shear strength of the soil, which is due to the interaction between the soil and clay minerals, which makes the soil particles have a certain structural strength. In this paper, the shear strength of three soil layers (red soil layer, sand layer, clastic layer) is studied by triaxial shear test. When different amounts of ferric oxide colloid are found in the soil mass, the shear strength of each soil layer and the reason for the change are studied. The four samples with iron oxide content gradient were blank sample, 1/3Fed sample, 2/3Fed sample and Fed sample were removed, and the physical and chemical properties of free iron oxide colloid were changed before and after the removal of free iron oxide colloid. The factors that cause the shear strength of soil are analyzed by SEM. The main results are as follows: (1) after the removal of free iron oxide by DCB method, the clay content in the three soil layers increased obviously, while the large particle content decreased obviously, among which the clay layer changed most obviously. This is because after DCB treatment, the agglomerates formed by the interaction of iron oxide adsorbed by large particles with clay minerals are destroyed, and the clay particles previously adsorbed on the surface of coarse particles are released as part of the clay particles. The clay content was increased. (2) the microscopic cementation of ferric oxide colloid was one of the guarantee of soil structural strength. Due to the formation of hydrogen bonds and electrostatic force between goethite and kaolin, in SEM diagram, free iron oxide in the soil is mainly formed in the form of "bridge" or "coating" to form a connection state between clay minerals and other particles and form the gravitational force between them. To form agglomerate particles. Because the agglomeration experience is embedded in the pores and increases the sliding friction force of the contact surface, the macropores are filled into small pores, the porosity decreases, and the structure becomes more stable. However, when the iron oxide colloid is removed, the bonding hydrogen bond breaks, which leads to the breaking of the bonding hydrogen bond between the iron oxide colloid and the clay mineral, the disappearance of the gravitational force between the particles, the destruction of the bonding state, and the destruction of the structure of the aggregate. (3) from the overall analysis, it can be concluded that the shear strength of the specimen decreases with the increase of moisture content, while the shear strength of the sample with complete removal of Fed increases firstly and then decreases with the increase of moisture content. The results showed that the soil shear strength could be changed by influencing the morphology of the particles, the arrangement of the composite structure, the porosity and other factors under the different moisture content of ferric oxide colloid. The iron oxide colloid mainly changes the shear strength of soil by changing the cohesion of soil and the angle of internal friction. When the moisture content is constant, the cohesive force and the angle of internal friction of the three soil samples decrease with the increase of the specific gravity of the sample containing the removal of ferric oxide colloidal soil, but the complete removal of the sample is due to the complete release of the clay particles. The water adsorption ability of clay particles increases, the capillary cohesion increases, and the uniform porosity of particle structure is small, which makes it easy to form intermolecular gravity. The cohesion of some samples was increased under suitable conditions. (4) the cementation of ferric oxide colloid with clay minerals played an important role in the structural strength of the rockfall soil. The results show that with the decrease of the content of ferric oxide colloid in the sample, the shear strength of the blank sample, the 1/3Fed sample, the 2/3Fed sample, and the Fed sample is decreasing as a whole. However, the downward trend is not always decreasing gradually, but is related to the stage of free ferric oxide colloid, which makes it have the ability of stage and integrity. In addition, when the free iron oxide is removed completely in the three soil layers, the deflection stress of the sample increases.
【學(xué)位授予單位】：福建農(nóng)林大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：S157
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