黄土EPS颗粒混合轻质土的性能研究

发布时间：2018-07-16 20:04

【摘要】：我国西北地域主要分布的是黄土,而黄土分布区域常见的一种地质灾害就是黄土发生滑坡。陕西泾阳南塬黄土塬区上洞穴及裂缝很发育,有时还能看到孤立的黄土柱,被称为黄土“喀斯特”地貌。而黄土塬上广泛分布的洞穴、裂缝能够引诱黄土发生滑坡,因此填充洞穴、裂缝对减少滑坡灾害的发生有很大的实际意义。本文以陕西省泾阳南塬地区的黄土斜坡为研究对象,提出了用黄土EPS颗粒混合轻质土来填充裂缝与洞穴的处治方法,通过流值测定实验、室内抗剪强度实验、三轴渗透试验以及基质吸力实验等对其流动性、强度以及渗透能力进行了研究,采用GeoStudio软件建模分析,得到填充材料的最优配合比,并为预防治理黄土滑坡提供理论依据,进而达到研究黄土“喀斯特”处治及其黄土斜坡稳定性研究的目的。研究成果主要如下:(1)混合轻质土的流动能力随着水泥、EPS颗粒掺入比的减小而上升,随着掺水比的减小而下降,并得到了黄土EPS颗粒混合轻质土的流动能力的预测计算公式。(2)无侧限抗压强度随着龄期的延长而不断变大,在养生初期增加较快,且与7-28天的养生龄期的关系可用对数函数来描述,随着养生时间的增加,无侧限抗压强度增加的速度慢慢减小;而且当掺水比变大、水泥掺入比变小以及EPS泡沫颗粒掺入比变大的时候,无侧限抗压强度的大小下降,反之,则上升;其与各掺入比的关系可用幂函数表示。(3)在围压相同的情况下,当掺水比变小或者水泥掺入比变大的时候,试件的应力-应变曲线会由应变硬化型朝着应变软化型的方向发生改变。随着围压的不断变大,所有配合比的试件的应力—应变的曲线关系都由应变软化型向应变硬化型转变,且其所对应的抗剪强度也随着不断变大。当围压为50-200kPa时,可用摩尔库伦理论来分析试件的抗剪强度指标;当围压大于等于300kPa时,摩尔库伦理论已不适用。(4)掺水比对抗剪强度指标c、φ的影响较之水泥或EPS颗粒掺入比的影响而言很小。当水泥掺入比变大或者EPS颗粒掺入比变小的时候,黏聚力c会变大。而内摩擦角φ则与之相反。(5)饱和渗透系数k的数量级大致为10-9~10-8(m/s),在围压作用下比无围压时要小,且随着围压的增大而减小,并与之呈幂函数关系;当水泥掺入比变小或者EPS颗粒掺入比变大的时候,饱和渗透系数k会变大,但受掺水比的影响较小。土水特征曲线(SWCC)几乎不受掺水比变化的影响。(6)利用有限元GeoStudio软件建模分析,得到了掺水比为70%,水泥掺入比为20%,EPS颗粒掺入比为3%的最优配合比。
[Abstract]:Loess is the main distribution of loess in northwest China, and a common geological hazard in loess distribution area is loess landslide. Caves and cracks are well developed in the loess plateau area of Jingyang, Shaanxi Province, and the isolated loess column can be seen sometimes, which is called "karst" landform of loess. However, cracks in widely distributed caves on the loess plateau can induce loess landslides, so filling caves and cracks are of great practical significance to reduce the occurrence of landslide disasters. In this paper, the loess slope in the south plateau area of Jingyang, Shaanxi Province is taken as the research object, and the treatment method of filling cracks and caves with the mixed lightweight soil of loess EPS particles is put forward. The flow value measurement experiment and the shear strength test are carried out in the laboratory. The fluidity, strength and permeability of the material were studied by triaxial permeation test and matrix suction test. The optimum mixture ratio of filling material was obtained by using GeoStudio software, and the theoretical basis was provided for preventing and controlling loess landslide. The purpose of this paper is to study the treatment of loess karst and the stability of loess slope. The main results are as follows: (1) the flow capacity of mixed light soil increases with the decrease of EPS particle ratio, and decreases with the decrease of water ratio. The formula for predicting the flow capacity of loess EPS granular mixed lightweight soil is obtained. (2) the unconfined compressive strength increases with the extension of age and increases rapidly in the early stage of health preservation. And the relationship with 7-28 days health age can be described by logarithmic function. With the increase of health time, the increasing speed of unconfined compressive strength decreases, and when the ratio of water to water increases, When cement blending ratio becomes smaller and EPS foam particle blending ratio becomes larger, the unconfined compressive strength decreases, whereas it rises, and its relationship with each ratio can be expressed by power function. (3) under the same confining pressure, The stress-strain curve of the specimen will change from strain hardening to strain softening when the ratio of water to cement decreases or the ratio of cement to cement becomes larger. With the increasing of confining pressure, the stress-strain curve changes from strain softening type to strain hardening type, and the corresponding shear strength increases with the increasing of confining pressure. When the confining pressure is 50 ~ 200 KPA, the shear strength index of the specimen can be analyzed by using the molar Coulomb theory, and when the confining pressure is greater than or equal to 300 KPA, The molar Coulomb theory is no longer applicable. (4) the influence of water ratio on shear strength c and 蠁 is smaller than that of cement or EPS particles. When the ratio of cement to cement or EPS particle is decreased, the cohesive force c will increase. The internal friction angle 蠁 is opposite. (5) the saturation permeability coefficient k is about 10 ~ (-9) ~ 10 ~ (-8) (m / s), which is smaller under confining pressure than that without confining pressure, and decreases with the increase of confining pressure, and has a power function relationship with it. When the ratio of cement and EPS particles increases, the saturation permeability coefficient k increases, but is less affected by water ratio. The soil-water characteristic curve (SWCC) is almost independent of the variation of water ratio. (6) the optimum mixing ratio of 70% water and 20% EPS particles is obtained by using the finite element software GeoStudio.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P642.22;TU444

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