本文選題：吸應力特征曲線 + 液限��； 參考：《蘭州理工大學》2017年碩士論文

【摘要】：目前在土工基本試驗項目中,液塑限的測定方法未能統(tǒng)一,傳統(tǒng)的液限和塑限的測定方法,如滾搓法、沉錐法等,由于受人為因素干擾較大,試驗中土樣的液塑限結果處于一個很寬的范圍。液塑限以及由其計算得到的液性指數(shù)和塑性指數(shù)等是土力學中評價細粒土結合水含量、膠體粘粒含量以及對其進行工程分類等方面的主要物理指標。因此,準確測定土體的液塑限就具有重要的意義。吸力是非飽和土力學中的核心問題,可通過土-水特征曲線(soil-water Characteristic Curve,SWCC)直觀的觀察吸力的變化特征;近些年Lu等研究發(fā)現(xiàn),吸應力特征曲線(Suction Stress Characteristic Curve,SSCC)是非飽和土重要的本構關系,能更確切的描述土中的吸力和應力狀態(tài)。本文通過對吸應力特征曲線(SSCC)的研究發(fā)現(xiàn),隨著含水量的增加,根據(jù)土體中孔隙水的賦存狀態(tài)和固-液相互作用機制,可以將土體吸應力特征曲線劃分成不同階段,且揭示了每個階段的特征點與界限含水量之間內在聯(lián)系。基于以上思路本文的工作如下:(1)對目前常用的幾種測定土體液塑限的基本試驗方法及其缺陷進行了分析和總結。(2)根據(jù)分析需要,制取不同的初始條件的土樣,采用液塑限聯(lián)合測定方法測定土體的液塑限,而后利用改裝的非飽和土三軸儀測定不同初始條件下土樣的土-水特征曲線(SWCC),同時分析了曲線在不同干密度、凈圍壓的變化特征,根據(jù)前人的試驗分析與自己試驗對比確認試驗的準確性。(3)采用RETC軟件對試驗得到的數(shù)據(jù)進行擬合,得出V-G模型的參數(shù),并分析了參數(shù)的變化規(guī)律。據(jù)得到的試驗數(shù)據(jù),基于Lu提出的吸應力(s?)與含水量(w)之間的關系表達式,繪制吸應力特征曲線,并分析曲線在不同干密度、凈圍壓時的變化。(4)將土體吸應力特征曲線劃分成5個階段,分析了各階段特征點相應的含水量與土體界限含水量之間的對應關系,揭示了土體稠度狀態(tài)和界限含水量的物理本質,詳細論述了土體可塑階段與液塑限之間的內在聯(lián)系。作為對比引用了已有的土-水特征曲線試驗數(shù)據(jù)進行分析,結果進一步表明了基于吸應力特征曲線確定細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.
【學位授予單位】：蘭州理工大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TU43

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