本文選題：膨脹土 + 動剪切模量�。� 參考：《華北水利水電大學》2016年碩士論文

【摘要】：膨脹土是一種特殊的黏性土,其黏粒成分主要為強親水性礦物蒙脫石,具有多裂隙性、超固結(jié)性、吸水膨脹軟化、失水干縮開裂,且反復變形的特性。盡管膨脹土的巖土工程災害和工程地質(zhì)災害已經(jīng)被人們所了解,但對其在動荷載作用下將會表現(xiàn)出的致災性和易損性還缺少全面和深入的了解。膨脹土因其顯著的脹縮性表現(xiàn)出非常差的工程特性,所以不難想象膨脹土在動荷載的作用下勢必很容易引起土體瞬間失穩(wěn)或土體疲勞破壞等異常的變形甚至產(chǎn)生工程病害,對地下工程及地表結(jié)構(gòu)產(chǎn)生損害,以致導致財產(chǎn)損失甚至對人民生命安全產(chǎn)生威脅。所以對膨脹土進行動力學研究是極其必要的,這有著非常重要的科學意義和實用價值。本文用GDS共振柱系統(tǒng),對不同自由膨脹率、含水率、干密度和圍壓下膨脹土的動剪切模量和阻尼比進行研究,并取得了一些結(jié)論。(1)原土與加入不同比例的膨潤土進行對比試驗后發(fā)現(xiàn),在小應變條件下,自由膨脹率越大,試樣的動剪模量也越大。自由膨脹率為110%的試樣的動剪切模量明顯高于自由膨脹率分別為85%和60%試樣的動剪切模量。試樣的動剪切模量隨著自由膨脹率的增大而增大,且增大的幅度明顯增加。但是當動剪應變增大到一定值時,這種增加的幅度變小了。而且自由膨脹率越大,試樣的阻尼比就越大。自由膨脹率為110%的試樣的阻尼比高于自由膨脹率分別為85%和60%試樣的阻尼比。(2)在應變條件為10-4-10-2下,當試樣含水率為20%、23%、26%時,隨著含水率的增大,試樣動剪切模量不斷減小,而且減小幅度明顯增加。同時試樣含水率越大,阻尼比越小。含水率為26%的試樣的阻尼比明顯小于含水率為23%和20%試樣的阻尼比。隨著含水率的增大,試樣阻尼比減小,而且減小的趨勢上升。隨著含水率的增大,含水率對膨脹土阻尼比的影響是逐漸增強的。(3)當應變?yōu)樾儠r,在試樣的干密度為1.45 g/cm3、1.57 g/cm3、1.69 g/cm3的條件下,干密度增大時,試樣的動剪切模量也隨之增大,而且增大的趨勢基本相同。當試樣干密度增大時,阻尼比也隨之增大。隨著干密度的增大,試樣的阻尼比也隨之增大,而且增大的趨勢基本相同。(4)在小應變下,固結(jié)圍壓為50 kPa、100 kPa、200 kPa,隨著圍壓的增大,試樣的動剪切模量也隨之增大,而且增大的趨勢呈上升狀態(tài)。但是當動剪應變增大到一定值時,這種趨勢又減弱了。當圍壓增大時,試樣阻尼比也隨之增大。(5)用雙曲線模型對1/G與γ進行擬合,把結(jié)果整理分析后看出,不同自由膨脹率、含水率、干密度和圍壓下,1/G與γ均成良好的直線關(guān)系。試驗點與直線有較好的擬合性,離散程度較小。說明雙曲線模型能夠很好地描述不同自由膨脹率、含水率、干密度和圍壓下膨脹土的動應力應變關(guān)系。
[Abstract]:Expansive soil is a kind of special clay. Its clay is mainly composed of strong hydrophilic mineral montmorillonite. It has the characteristics of multiple fissures, overconsolidation, swelling and softening of water absorption, dry shrinkage and cracking of lost water, and repeated deformation. Although the geotechnical engineering disasters and engineering geological disasters of expansive soil have been well known, there is still a lack of comprehensive and in-depth understanding of the disaster-causing and vulnerability of expansive soils under dynamic loads. Because of its remarkable dilatancy and shrinkage, expansive soil shows very poor engineering characteristics, so it is not difficult to imagine that expansive soil under the action of dynamic load will easily lead to transient instability of soil or abnormal deformation of soil such as fatigue failure of soil, and even produce engineering diseases. Damage to underground works and surface structures, resulting in property losses and even a threat to the safety of people. Therefore, it is extremely necessary to study the dynamics of expansive soil, which has very important scientific significance and practical value. In this paper, the dynamic shear modulus and damping ratio of expansive soil under different free expansion ratio, moisture content, dry density and confining pressure are studied by GDS resonance column system. Some conclusions have been obtained. (1) comparing the original soil with the bentonite with different proportion, it is found that under the condition of small strain, the larger the free expansion ratio is, the greater the dynamic shear modulus of the sample is. The dynamic shear modulus of the specimen with free expansion rate of 110% is significantly higher than that of the specimen with free expansion rate of 85% and 60%, respectively. The dynamic shear modulus of the specimen increases with the increase of the free expansion rate, and the amplitude of the increase is obviously increased. But when the dynamic shear strain increases to a certain value, the amplitude of this increase becomes smaller. Moreover, the larger the free expansion rate, the greater the damping ratio of the sample. The damping ratio of the specimen with 110% free expansion ratio is higher than that of the sample with free expansion rate of 85% and 60%, respectively. When the strain condition is 10-4-10-2, when the moisture content of the sample is 20% and 26cm, the dynamic shear modulus of the specimen decreases with the increase of the moisture content. And the decrease is obviously increased. At the same time, the higher the moisture content of the sample, the smaller the damping ratio. The damping ratio of the sample with water content of 26% is obviously lower than that of the sample with moisture content of 23% and 20%. With the increase of moisture content, the damping ratio of the sample decreases and the decreasing trend increases. With the increase of moisture content, the effect of moisture content on the damping ratio of expansive soil is gradually enhanced. When the strain is small, the dynamic shear modulus of the specimen increases when the dry density of the sample is 1.45 g / cm ~ (3) ~ (-1) g / cm ~ (3) and 1.57 g / cm ~ (3) C ~ (3 +) 1.69 g/cm3. And the trend of increase is basically the same. When the dry density of the sample increases, the damping ratio also increases. With the increase of dry density, the damping ratio of the sample increases, and the increasing trend is basically the same. 4) under small strain, the consolidation confining pressure is 50kPa100kPa100kPa200kPa. with the increase of confining pressure, the dynamic shear modulus of the sample increases. And the increasing trend is on the rise. But when the dynamic shear strain increases to a certain value, this trend weakens again. When the confining pressure increases, the damping ratio of the sample also increases. 5) the hyperbolic model is used to fit 1 / G and 緯. The results show that the free expansion ratio, moisture content, dry density and confining pressure of 1 / G and 緯 are all in good linear relationship. The test points fit well with the straight line, and the dispersion degree is small. The hyperbolic model can well describe the dynamic stress-strain relationship of expansive soil under different free expansion ratio, water content, dry density and confining pressure.
【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】：2016
【分類號】：TU443

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