基于吸应力特征曲线确定土体界限含水量方法的研究

发布时间：2018-06-17 21:09

本文选题：吸应力特征曲线 + 液限　；参考：《兰州理工大学》2017年硕士论文

【摘要】：目前在土工基本试验项目中,液塑限的测定方法未能统一,传统的液限和塑限的测定方法,如滚搓法、沉锥法等,由于受人为因素干扰较大,试验中土样的液塑限结果处于一个很宽的范围。液塑限以及由其计算得到的液性指数和塑性指数等是土力学中评价细粒土结合水含量、胶体粘粒含量以及对其进行工程分类等方面的主要物理指标。因此,准确测定土体的液塑限就具有重要的意义。吸力是非饱和土力学中的核心问题,可通过土-水特征曲线(soil-water Characteristic Curve,SWCC)直观的观察吸力的变化特征;近些年Lu等研究发现,吸应力特征曲线(Suction Stress Characteristic Curve,SSCC)是非饱和土重要的本构关系,能更确切的描述土中的吸力和应力状态。本文通过对吸应力特征曲线(SSCC)的研究发现,随着含水量的增加,根据土体中孔隙水的赋存状态和固-液相互作用机制,可以将土体吸应力特征曲线划分成不同阶段,且揭示了每个阶段的特征点与界限含水量之间内在联系。基于以上思路本文的工作如下:(1)对目前常用的几种测定土体液塑限的基本试验方法及其缺陷进行了分析和总结。(2)根据分析需要,制取不同的初始条件的土样,采用液塑限联合测定方法测定土体的液塑限,而后利用改装的非饱和土三轴仪测定不同初始条件下土样的土-水特征曲线(SWCC),同时分析了曲线在不同干密度、净围压的变化特征,根据前人的试验分析与自己试验对比确认试验的准确性。(3)采用RETC软件对试验得到的数据进行拟合,得出V-G模型的参数,并分析了参数的变化规律。据得到的试验数据,基于Lu提出的吸应力(s?)与含水量(w)之间的关系表达式,绘制吸应力特征曲线,并分析曲线在不同干密度、净围压时的变化。(4)将土体吸应力特征曲线划分成5个阶段,分析了各阶段特征点相应的含水量与土体界限含水量之间的对应关系,揭示了土体稠度状态和界限含水量的物理本质,详细论述了土体可塑阶段与液塑限之间的内在联系。作为对比引用了已有的土-水特征曲线试验数据进行分析,结果进一步表明了基于吸应力特征曲线确定细粒土液塑限的可行性。
[Abstract]:At present, in the basic geotechnical test items, the determination method of liquid plastic limit is not uniform. The traditional measuring methods of liquid limit and plastic limit, such as roll rubbing method, sinking cone method, etc., are greatly interfered by human factors. The results of liquid plastic limit of soil samples are in a wide range. The liquid-plastic limit and the calculated liquid and plastic indices are the main physical indexes in soil mechanics for evaluating the content of bound water colloidal clay and classifying it in engineering. Therefore, it is of great significance to accurately determine the liquid-plastic limit of soil. Suction is the core problem in unsaturated soil mechanics, and the variation of suction can be observed intuitively by soil-water characteristic curve SWCC.In recent years, Lu et al found that the absorption stress characteristic curve is an important constitutive relation of unsaturated soil. Can more accurately describe the soil suction and stress state. In this paper, it is found that with the increase of water content, the characteristic curve of absorbing stress can be divided into different stages according to the existing state of pore water in soil and the mechanism of solid-liquid interaction. The relationship between the characteristic points of each stage and the limit water content is revealed. Based on the above ideas, the work of this paper is as follows: (1) the basic test methods and their defects for measuring the soil fluid plastic limit are analyzed and summarized. (2) according to the needs of the analysis, soil samples with different initial conditions are prepared. The liquid plastic limit of soil was determined by the combined method of liquid and plastic limit, and then the soil water characteristic curve of soil sample under different initial conditions was measured by a modified unsaturated soil triaxial apparatus. The variation characteristics of the curve under different dry density and net confining pressure were analyzed. According to the accuracy of the test compared with our own test, we use RETC software to fit the test data, get the parameters of V-G model, and analyze the variation law of the parameters. According to the experimental data obtained, based on Lu's theory of absorptive stress The relationship between water content and water content (w), draw the characteristic curve of absorbing stress, and analyze the change of curve at different dry density and net confining pressure. 4) divide the characteristic curve of absorbing stress of soil into five stages. The relationship between the corresponding water content of each stage characteristic point and the limit water content of soil is analyzed, the physical essence of the soil consistency state and the limit water content is revealed, and the internal relation between the plastic stage of soil and the liquid plastic limit is discussed in detail. The experimental data of soil-water characteristic curves are compared and analyzed. The results show that it is feasible to determine the liquid-plastic limit of fine grained soil based on the characteristic curve of absorptive stress.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU43

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