本文選題：紫色土 + 抗剪強(qiáng)度��； 參考：《重慶師范大學(xué)》2017年碩士論文

【摘要】：紫色土坡耕地是三峽庫(kù)區(qū)水土流失防治的重點(diǎn),埂坎是坡耕地水土保持的重要措施。土質(zhì)埂坎占三峽庫(kù)區(qū)現(xiàn)有坡耕地埂坎比例超過(guò)65%,控制坡耕地土壤侵蝕效果明顯。埂坎穩(wěn)定是其發(fā)揮水土保持作用的前提,抗剪強(qiáng)度是衡量土質(zhì)埂坎穩(wěn)定性的重要指標(biāo)。本研究選擇紫色土區(qū)典型坡耕地埂坎為研究對(duì)象,通過(guò)室內(nèi)三軸不固結(jié)不排水試驗(yàn)(UU)研究了不同含水率和干密度、二者交互作用以及加筋對(duì)埂坎土壤抗剪特征的影響。主要結(jié)果如下:(1)相同干密度狀況下,隨著土壤含水率的增加,埂坎土壤黏聚力(c)先增后減,呈二次曲線變化,峰值出現(xiàn)在含水率11%左右。當(dāng)含水率達(dá)到26%時(shí),埂坎土壤黏聚力衰減速率較快,土體抗剪強(qiáng)度明顯衰減;土壤內(nèi)摩擦角(φ)隨含水率的增加逐漸減小,符合一階指數(shù)衰減規(guī)律。當(dāng)含水率質(zhì)量分?jǐn)?shù)達(dá)到26%時(shí),內(nèi)摩擦角衰減趨勢(shì)放緩;埂坎土壤極限主應(yīng)力差(σ1-σ3)也表現(xiàn)為先增后減。(2)相同含水率狀況下,隨著干密度的增加,土壤黏聚力、內(nèi)摩擦角和極限主應(yīng)力差均有所增大,但增加的幅度各不相同。相對(duì)而言,含水率比干密度對(duì)土壤黏聚力、內(nèi)摩擦角和極限主應(yīng)力差的影響更大,但含水率和干密度的交互效應(yīng)對(duì)土壤黏聚力、內(nèi)摩擦角和極限主應(yīng)力差的影響很小,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應(yīng)力-應(yīng)變曲線特征有所不同,隨含水率遞增依次呈現(xiàn)應(yīng)變軟化型、硬化型和弱硬化型,而隨干密度遞增埂坎土壤的應(yīng)力-應(yīng)變曲線依次呈現(xiàn)硬化型、弱硬化型和應(yīng)變軟化型,且隨著圍壓的遞增更多呈現(xiàn)硬化型。(4)土壤黏聚力比土壤內(nèi)摩擦角更容易受到加筋材料的影響,3種試驗(yàn)材料加筋土均體現(xiàn)出土壤黏聚力隨著加筋含量的增加先增大后減小,土壤內(nèi)摩擦角隨加筋含量無(wú)明顯變化。不同加筋材料類型處理下埂坎土壤黏聚力大小為:c麥殼c竹絲c稻稈c素土,極限主應(yīng)力差在4種圍壓下均體現(xiàn)出(σ1-σ3)_(麥殼)(σ1-σ3)_(竹絲)(σ1-σ3)_(稻稈)(σ1-σ3)_(素土),不同加筋材料均能提升土壤抗剪強(qiáng)度,相比素土強(qiáng)度都有所增強(qiáng),但各類加筋材料之間提升強(qiáng)度水平各不相同,其中麥殼加筋效果最好,其次是竹絲,最后是稻稈。3種加筋土均表現(xiàn)出土壤極限主應(yīng)力差隨著加筋含量的增加先增大后減小,出現(xiàn)了最優(yōu)加筋含量,分別為麥殼0.8%、竹絲0.5%、稻稈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.
【學(xué)位授予單位】：重慶師范大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：S157

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