【摘要】：四川盆地西部山區(qū)地處青藏高原東緣,是我國境內(nèi)地震災(zāi)害及地震造成的次生地質(zhì)災(zāi)害頻發(fā)地區(qū),隸屬于世界兩大主要地震帶之一的地中海-喜馬拉雅山地震帶系,該地區(qū)素來以地質(zhì)構(gòu)造復(fù)雜、地震頻發(fā)著稱。該地區(qū)廣泛分布一種特有的崩坡積混合土,且在自然條件下常處于非飽和狀態(tài)。本論文主要對川西非飽和混合土展開了動剪切模量和阻尼比分析。本論文完成的主要工作及獲得的主要成果與結(jié)論如下：首先,對取自五個不同滑坡點的崩坡積混合土進(jìn)行了常規(guī)物理力學(xué)性質(zhì)試驗,主要包括礦物成分分析、天然含水率、天然密度、土顆粒密度、土顆粒級配試驗、界限含水率試驗等。通過礦物成分、顆粒級配、液塑限等差異性比選選出了三種物性差異明顯、有代表性的三種混合土(文中所列3號土、4號土和5號土,其細(xì)粒成分分別以粘土、粉土和粉質(zhì)粘土為主)進(jìn)行動力特性試驗研究。其次,運(yùn)用動三軸儀,模擬地震荷載作用下小變形范圍內(nèi)的三種混合土的動變形特性,采用Hardin-Drnevich雙曲線模型、運(yùn)用數(shù)學(xué)軟件Mathematica擬合得到Gd/Gmax-yd和λ～yd等曲線。在擬合曲線的基礎(chǔ)上,研究了飽和度、細(xì)顆粒含量、干密度、循環(huán)振動次數(shù)、固結(jié)比和振動頻率等因素對川西混合土的動剪切模量和阻尼比的影響。尤其重點研究了飽和度和細(xì)顆粒含量的影響效果,發(fā)現(xiàn)隨著飽和度的增加,川西混合土的動剪切模量減小、阻尼比增大；隨著細(xì)顆粒含量最大粒徑的增大,混合土的動剪切模量和阻尼比均增大。還將試驗結(jié)果與文獻(xiàn)值進(jìn)行了比對。最后,對三種典型的川西混合土的動力特性試驗數(shù)據(jù)分別按飽和狀態(tài)和非飽和狀態(tài)分組匯總,擬合各組匯總數(shù)據(jù)獲得了三種土分別在飽和狀態(tài)和非飽和狀態(tài)下的動剪切模量比函數(shù)Gd/Gmax＝Gd/Gmax(yd)和阻尼比函數(shù)λ～λ(yd),給出了川西混合土的動剪切模量比和阻尼比的推薦值。該推薦值可作為該地區(qū)工程抗震設(shè)計和地震安全評估的參考值。
[Abstract]:The western mountainous area of Sichuan Basin is located in the eastern margin of the Qinghai-Xizang Plateau. It is a frequent area of earthquake disasters and secondary geological disasters caused by earthquakes in China. It belongs to the Mediterranean Himalayan seismic belt, one of the two major seismic zones in the world. The area has long been known for its complex geological structure and frequent earthquakes. A special sloping mixed soil is widely distributed in this area, and it is often in unsaturated state under natural conditions. In this paper, the dynamic shear modulus and damping ratio of unsaturated mixed soils in western Sichuan are analyzed. The main achievements and conclusions of this paper are as follows: firstly, the conventional physical and mechanical properties tests of caving mixed soil from five different landslide points are carried out, including mineral composition analysis, natural moisture content, and so on. Natural density, soil particle gradation test, limit moisture content test, etc. Through the difference of mineral composition, particle gradation and liquid plastic limit, three kinds of mixed soil were selected. The three kinds of mixed soil (soil No. 3, soil No. 4 and soil No. 5 listed in this paper) were composed of clay respectively. The dynamic characteristics of silt and silty clay are studied. Secondly, the dynamic deformation characteristics of three mixed soils in small deformation range under seismic load are simulated by using dynamic triaxial instrument. The Gd/Gmax-yd and 位 ~ yd curves are obtained by using Hardin-Drnevich hyperbolic model and mathematical software Mathematica. On the basis of fitting curves, the effects of saturation, fine particle content, dry density, cyclic vibration frequency, consolidation ratio and vibration frequency on the dynamic shear modulus and damping ratio of mixed soils in western Sichuan were studied. Especially, the effect of saturation and fine particle content is studied. It is found that with the increase of saturation, the dynamic shear modulus of mixed soil decreases and the damping ratio increases. The dynamic shear modulus and damping ratio of mixed soil increase with the increase of the maximum particle size of fine particle content. The experimental results were compared with those of the literature. Finally, the experimental data of dynamic characteristics of three typical mixed soils in western Sichuan are summarized according to the saturated state and unsaturated state, respectively. The dynamic shear modulus ratio function (Gd/Gmax=Gd/Gmax (yd) and damping ratio function 位 ~ 位 (yd), of three kinds of soils under saturated and unsaturated conditions were obtained by fitting the data collected in each group. The recommended values of dynamic shear modulus ratio and damping ratio of mixed soil in western Sichuan are given. The recommended values can be used as reference values for seismic design and seismic safety assessment of engineering in this area.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2015
【分類號】：TU411

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