本文選題：黃土 + 含水量　； 參考：《華北水利水電大學》2017年碩士論文

【摘要】：近些年來,西部黃土地區(qū)(如甘肅、陜西等地)滑坡等地質(zhì)災(zāi)害發(fā)生頻繁,對當?shù)厝藗兊纳拓敭a(chǎn)安全帶來了巨大的威脅,已成為制約當?shù)亟?jīng)濟發(fā)展的重要影響因素,因此分析滑坡的發(fā)生機理以及黃土力學特性的影響因素具有重要的理論與工程實際意義。本文以甘肅黑方臺黃土為對象,通過現(xiàn)場調(diào)查、室內(nèi)試驗,研究了含水量及含鹽量對黃土力學特性的影響規(guī)律。本文主要內(nèi)容如下:(1)通過對不同含水量原狀黃土的環(huán)剪試驗,研究了黃土在不同含水量狀態(tài)下的強度弱化規(guī)律,系統(tǒng)地分析了含水量對原狀黃土力學特性的影響,分析發(fā)現(xiàn):低含水量狀態(tài)下的原狀黃土呈應(yīng)變軟化特性,隨著含水量的升高,其對應(yīng)的應(yīng)變軟化特性逐漸減弱,剪應(yīng)力-應(yīng)變曲線逐漸向應(yīng)變硬化型轉(zhuǎn)變,在相同法向應(yīng)力作用下,土樣含水量越低,剪應(yīng)力峰值越高,剪應(yīng)力增長速度也越快,越快達到峰值;原狀黃土的抗剪強度隨著含水量的升高不斷降低,但降低幅度逐漸減小,說明水對低含水量的黃土抗剪強度軟化效應(yīng)比高含水量黃土更加明顯;隨著含水量的升高,原狀黃土的粘聚力逐漸下降,內(nèi)摩擦角也逐漸降低,但降低幅度是不相同的,相對于粘聚力來說,內(nèi)摩擦角隨含水量增大而產(chǎn)生的降幅較小,這表明含水量對粘聚力具有較大的靈敏性。(2)通過對不同含鹽量原狀黃土的環(huán)剪試驗,研究了黃土在不同含鹽量下的強度變化規(guī)律,系統(tǒng)地分析了含鹽量對原狀黃土力學特性的影響,分析發(fā)現(xiàn):在相同法向應(yīng)力作用下,土樣含鹽量越高,剪應(yīng)力峰值越高,剪應(yīng)力增長速度也越快,同一含鹽量狀態(tài)下,法向應(yīng)力越大,剪應(yīng)力峰值越大,剪應(yīng)力增大速度越快;隨著含鹽量的降低,原狀黃土的抗剪強度不斷降低,減小值隨法向應(yīng)力的增大而增大,此外鹽分降低對高含鹽量的黃土抗剪強度弱化作用比低含鹽量黃土更明顯;隨著含鹽量的降低,土體粘聚力和內(nèi)摩擦角均逐漸降低,但內(nèi)摩擦角降低幅度很小,這表明含鹽量對粘聚力具有較大的靈敏性。
[Abstract]:In recent years, geological disasters such as landslides in the loess region of western China (such as Gansu, Shaanxi and other places) have occurred frequently, which have brought a great threat to the safety of local people's lives and property, and have become an important influencing factor restricting the development of local economy. Therefore, it is of great theoretical and practical significance to analyze the occurrence mechanism of landslide and the influencing factors of loess mechanical properties. Taking Heifangtai loess in Gansu province as an example, the influence of water content and salt content on the mechanical properties of loess was studied by field investigation and laboratory tests. The main contents of this paper are as follows: (1) through the annular shear test of loess with different moisture content, the strength weakening law of loess under different water content is studied, and the influence of water content on the mechanical properties of undisturbed loess is systematically analyzed. It is found that under the condition of low water content, the undisturbed loess shows strain-softening characteristics. With the increase of water content, the corresponding strain-softening characteristic decreases gradually, and the shear stress-strain curve gradually changes to the strain-hardening type. Under the same normal stress, the lower the water content of soil sample, the higher the peak value of shear stress, the faster the growth rate of shear stress and the faster the peak value of shear stress, the shear strength of undisturbed loess decreases with the increase of water content, but the decreasing range decreases gradually. The results show that the softening effect of water on the shear strength of loess with low water content is more obvious than that of loess with high water content, and with the increase of water content, the cohesion and internal friction angle of undisturbed loess decrease gradually, but the decrease range is different. Relative to cohesion, the decrease of internal friction angle is smaller with the increase of water content, which indicates that water content has greater sensitivity to cohesion. In this paper, the strength variation law of loess under different salt content is studied, and the influence of salt content on the mechanical properties of undisturbed loess is systematically analyzed. It is found that under the same normal stress, the higher the salt content of soil sample is, the higher the peak value of shear stress is. Under the same salt content, the greater the normal stress, the greater the peak value of shear stress and the faster the increase of shear stress, and with the decrease of salt content, the shear strength of undisturbed loess decreases continuously. The decreasing value increases with the increase of normal stress, in addition, the weakening effect of salinity on the shear strength of loess with high salt content is more obvious than that of loess with low salt content, and with the decrease of salt content, the cohesive force and internal friction angle of soil gradually decrease. However, the reduction of internal friction angle is very small, which indicates that salt content is sensitive to cohesion.
【學位授予單位】：華北水利水電大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：S152

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