紫色土坡耕地埂坎土壤抗剪特征研究

发布时间：2018-04-11 20:34

本文选题：紫色土 + 抗剪强度　；参考：《重庆师范大学》2017年硕士论文

【摘要】：紫色土坡耕地是三峡库区水土流失防治的重点,埂坎是坡耕地水土保持的重要措施。土质埂坎占三峡库区现有坡耕地埂坎比例超过65%,控制坡耕地土壤侵蚀效果明显。埂坎稳定是其发挥水土保持作用的前提,抗剪强度是衡量土质埂坎稳定性的重要指标。本研究选择紫色土区典型坡耕地埂坎为研究对象,通过室内三轴不固结不排水试验(UU)研究了不同含水率和干密度、二者交互作用以及加筋对埂坎土壤抗剪特征的影响。主要结果如下:(1)相同干密度状况下,随着土壤含水率的增加,埂坎土壤黏聚力(c)先增后减,呈二次曲线变化,峰值出现在含水率11%左右。当含水率达到26%时,埂坎土壤黏聚力衰减速率较快,土体抗剪强度明显衰减;土壤内摩擦角(φ)随含水率的增加逐渐减小,符合一阶指数衰减规律。当含水率质量分数达到26%时,内摩擦角衰减趋势放缓;埂坎土壤极限主应力差(σ1-σ3)也表现为先增后减。(2)相同含水率状况下,随着干密度的增加,土壤黏聚力、内摩擦角和极限主应力差均有所增大,但增加的幅度各不相同。相对而言,含水率比干密度对土壤黏聚力、内摩擦角和极限主应力差的影响更大,但含水率和干密度的交互效应对土壤黏聚力、内摩擦角和极限主应力差的影响很小,基本可以忽略。(3)不同含水率和干密度下紫色土坡耕地埂坎土壤的应力-应变曲线特征有所不同,随含水率递增依次呈现应变软化型、硬化型和弱硬化型,而随干密度递增埂坎土壤的应力-应变曲线依次呈现硬化型、弱硬化型和应变软化型,且随着围压的递增更多呈现硬化型。(4)土壤黏聚力比土壤内摩擦角更容易受到加筋材料的影响,3种试验材料加筋土均体现出土壤黏聚力随着加筋含量的增加先增大后减小,土壤内摩擦角随加筋含量无明显变化。不同加筋材料类型处理下埂坎土壤黏聚力大小为:c麦壳c竹丝c稻秆c素土,极限主应力差在4种围压下均体现出(σ1-σ3)_(麦壳)(σ1-σ3)_(竹丝)(σ1-σ3)_(稻秆)(σ1-σ3)_(素土),不同加筋材料均能提升土壤抗剪强度,相比素土强度都有所增强,但各类加筋材料之间提升强度水平各不相同,其中麦壳加筋效果最好,其次是竹丝,最后是稻秆。3种加筋土均表现出土壤极限主应力差随着加筋含量的增加先增大后减小,出现了最优加筋含量,分别为麦壳0.8%、竹丝0.5%、稻秆0.3%。
[Abstract]:Purple soil slope farmland is the key point of soil erosion control in the three Gorges Reservoir area, and ridge ridge is an important measure for soil and water conservation of slope farmland.The proportion of soil ridge ridge in the existing sloping farmland in the three Gorges Reservoir area is more than 65, and the effect of controlling soil erosion on sloping land is obvious.The stability of ridge ridge is the premise of soil and water conservation, and the shear strength is an important index to measure the stability of ridge ridge.In this study, the typical sloping land ridge in purple soil area was selected as the research object, and the effects of different moisture content and dry density, interaction between them and reinforcement on soil shear resistance of ridge ridge were studied through the laboratory triaxial unconsolidated undrained test (UU).The main results were as follows: (1) under the same dry density, with the increase of soil moisture content, the soil cohesion increased first and then decreased, and the peak value appeared at about 11% of water content.When the moisture content is 26%, the cohesive strength of the soil decreases rapidly and the shear strength of the soil decreases obviously, and the friction angle (蠁) of the soil decreases with the increase of moisture content, which accords with the first order exponential attenuation law.When the mass fraction of water content reached 26, the attenuation trend of internal friction angle slowed down, and the limit principal stress difference (蟽 1- 蟽 3) of ridge ridge was increased first and then decreased. Under the same water content condition, with the increase of dry density, the cohesion of soil was increased.The angle of internal friction and the difference of ultimate principal stress are increased, but the range of increase is different.Comparatively speaking, moisture content has more influence on soil cohesion, internal friction angle and limit principal stress difference than dry density, but the interaction effect of water content and dry density has little effect on soil cohesion, internal friction angle and limit principal stress difference.The characteristics of stress-strain curve of ridge ridge soil in purple soil with different moisture content and dry density can be neglected. With increasing water content, the characteristics of stress-strain curve are in turn strain-softening type, hardening type and weak hardening type.With the increase of dry density, the stress-strain curve of the soil showed hardening type, weak hardening type and strain softening type.With the increasing of confining pressure, the soil cohesion is more likely to be affected by the reinforced material than the soil internal friction angle. All the three test materials show that the soil cohesion increases first and then decreases with the increase of the reinforcement content.The internal friction angle of soil did not change with the reinforcement content.The cohesive strength of the soil of different reinforced material types was: 1 / c wheat husk c bamboo silk c rice straw / c soil, and the soil cohesion was: 1 / c wheat husk c bamboo silk / rice straw / c soilHowever, the strength levels of all kinds of reinforced materials are different, among which wheat hull has the best reinforcement effect, followed by bamboo silk, and finally, the soil ultimate principal stress difference increases first and then decreases with the increase of reinforcement content, and finally, the soil ultimate principal stress difference increases with the increase of reinforcement content, and then decreases with the increase of reinforcement content.The results showed that the optimum gluten content was 0.8 for wheat husk, 0.5for bamboo silk and 0.3 for rice stalk.
【学位授予单位】：重庆师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：S157

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