非饱和黄土的动三轴试验研究
发布时间：2018-11-08 09:11
【摘要】：黄土在我国分布范围较广,多见于地震多发的中西部地区。特殊的形成条件决定了其特殊的结构体系,并表现出特殊的工程性质。西安作为黄土地区的重要城市,随着经济的快速发展及城市规模的扩大,城市地下轨道交通建设成为必然需求。目前黄土地区地铁车站、区间隧道等地下结构的抗震问题还未能深入研究,如何在地铁地下结构地震反应分析和抗震设计中体现西安黄土地质条件,合理反映黄土的动力特性还处于空白。基于上述情况,本研究采用土动力学方法,对西安非饱和黄土进行动力试验研究,提供适合西安地铁地下结构抗震分析的黄土动力特性参数。本文以西安市长安区的黄土作为研究对象,制成三种不同含水率的重塑试样及天然含水率的原状试样,在不同固结压力下进行动三轴试验;分析了非饱和黄土的动应力~动应变关系、动模量、阻尼比及动强度的变化规律,并对重塑黄土与原状黄土的试验结果进行了对比分析。研究表明:重塑黄土动应力~动应变关系基本符合双曲线关系,且受含水率影响较为明显,含水率越小,曲线在弹性阶段的斜率越大;随着围压的升高,重塑黄土动应力~动应变关系曲线高度亦随之升高。含水率及围压对重塑黄土的最大动模量有显著影响,在相同围压下,含水率增大,最大动模量减小;相同含水率时,围压升高,最大动模量随之增加。重塑黄土试样的阻尼比主要分布在0.05~0.15范围内,且随含水率的变化不明显,随围压的升高有增大的趋势。动强度试验中以黄土试样达到εdf=0.65%作为破坏标准,得到了重塑黄土在天然含水率下、不同破坏振次时的动抗剪强度指标。土质扰动对黄土动力特性参数有显著影响,与重塑黄土相比,原状黄土的各项动力特性参数及动强度指标均有不同程度提高。本文利用动三轴试验得到了西安地区非饱和黄土的动模量、阻尼比及动强度等动力特性指标,为西安地铁地下结构抗震研究及设计提供相关的土动力特性参数。同时,对于取样条件相似的黄土,无需进行试验,用经验公式即可得到相应的动力特性参数。
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU444;TU411.8
本文编号：2318029
[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.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU444;TU411.8
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