【摘要】：黃土在我國分布范圍較廣,多見于地震多發(fā)的中西部地區(qū)。特殊的形成條件決定了其特殊的結構體系,并表現(xiàn)出特殊的工程性質。西安作為黃土地區(qū)的重要城市,隨著經濟的快速發(fā)展及城市規(guī)模的擴大,城市地下軌道交通建設成為必然需求。目前黃土地區(qū)地鐵車站、區(qū)間隧道等地下結構的抗震問題還未能深入研究,如何在地鐵地下結構地震反應分析和抗震設計中體現(xiàn)西安黃土地質條件,合理反映黃土的動力特性還處于空白�；谏鲜銮闆r,本研究采用土動力學方法,對西安非飽和黃土進行動力試驗研究,提供適合西安地鐵地下結構抗震分析的黃土動力特性參數(shù)。本文以西安市長安區(qū)的黃土作為研究對象,制成三種不同含水率的重塑試樣及天然含水率的原狀試樣,在不同固結壓力下進行動三軸試驗;分析了非飽和黃土的動應力~動應變關系、動模量、阻尼比及動強度的變化規(guī)律,并對重塑黃土與原狀黃土的試驗結果進行了對比分析。研究表明:重塑黃土動應力~動應變關系基本符合雙曲線關系,且受含水率影響較為明顯,含水率越小,曲線在彈性階段的斜率越大;隨著圍壓的升高,重塑黃土動應力~動應變關系曲線高度亦隨之升高。含水率及圍壓對重塑黃土的最大動模量有顯著影響,在相同圍壓下,含水率增大,最大動模量減小;相同含水率時,圍壓升高,最大動模量隨之增加。重塑黃土試樣的阻尼比主要分布在0.05~0.15范圍內,且隨含水率的變化不明顯,隨圍壓的升高有增大的趨勢。動強度試驗中以黃土試樣達到εdf=0.65%作為破壞標準,得到了重塑黃土在天然含水率下、不同破壞振次時的動抗剪強度指標。土質擾動對黃土動力特性參數(shù)有顯著影響,與重塑黃土相比,原狀黃土的各項動力特性參數(shù)及動強度指標均有不同程度提高。本文利用動三軸試驗得到了西安地區(qū)非飽和黃土的動模量、阻尼比及動強度等動力特性指標,為西安地鐵地下結構抗震研究及設計提供相關的土動力特性參數(shù)。同時,對于取樣條件相似的黃土,無需進行試驗,用經驗公式即可得到相應的動力特性參數(shù)。
[Abstract]:Loess is widely distributed in our country, and it is often seen in the quake-prone central and western regions. The special forming conditions determine its special structure system and show special engineering properties. Xi'an is an important city in loess area. With the rapid development of economy and the expansion of urban scale, the construction of urban underground rail transit becomes an inevitable demand. At present, the seismic problems of underground structures such as subway stations and interval tunnels in loess area have not been studied in depth. How to reflect the geological conditions of Xi'an loess in seismic response analysis and seismic design of underground structures in Xi'an? It is still blank to reflect the dynamic characteristics of loess reasonably. Based on the above situation, the dynamic test of Xi'an unsaturated loess is carried out by using soil dynamics method, and the loess dynamic characteristic parameters suitable for seismic analysis of underground structure of Xi'an subway are provided. In this paper, loess in Chang'an district of Xi'an city is taken as the research object. Three kinds of remolded samples with different moisture content and undisturbed samples of natural moisture content are made, and dynamic triaxial tests are carried out under different consolidation pressures. The dynamic stress-strain relation, dynamic modulus, damping ratio and dynamic strength of unsaturated loess are analyzed, and the experimental results of remolded loess and undisturbed loess are compared and analyzed. The results show that the dynamic stress-strain relationship of remolded loess accords with the hyperbolic relation basically, and it is obviously influenced by water content. The smaller the moisture content is, the bigger the slope of the curve is in the elastic stage. With the increase of confining pressure, the height of dynamic stress-strain curve of remolded loess increases. Water content and confining pressure have significant influence on the maximum dynamic modulus of remolded loess. Under the same confining pressure, the water content increases and the maximum dynamic modulus decreases, and the maximum dynamic modulus increases with the increase of confining pressure at the same water content. The damping ratio of remolded loess is mainly distributed in the range of 0.050.15, and the change of the damping ratio is not obvious with the water content, but it increases with the increase of confining pressure. In the dynamic strength test, the dynamic shear strength index of remolded loess under natural moisture content was obtained by taking the loess specimen to 蔚 df=0.65% as the failure criterion. Compared with remolded loess, the dynamic characteristic parameters and dynamic strength indexes of undisturbed loess are improved to some extent. In this paper, the dynamic characteristics of unsaturated loess in Xi'an are obtained by dynamic triaxial test, such as dynamic modulus, damping ratio and dynamic strength, which provide relevant soil dynamic characteristic parameters for seismic research and design of underground structure of Xi'an subway. At the same time, for loess with similar sampling conditions, the corresponding dynamic characteristic parameters can be obtained by empirical formula without the need of test.
【學位授予單位】：長安大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：TU444;TU411.8

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本文編號：2318029