本文選題：軟土 + 雙尺度　； 參考：《浙江大學(xué)》2013年博士論文

【摘要】：土體力學(xué)行為的研究通常有宏觀尺度和微觀尺度兩條并行的研究主線。土體在宏觀尺度上表現(xiàn)的力學(xué)行為歸根結(jié)底是由其微觀尺度的顆粒與結(jié)構(gòu)的特性決定的。因此,宏觀尺度與微觀尺度相結(jié)合的研究,將微觀的物理試驗(yàn)與力學(xué)分析用于解釋土的宏觀力學(xué)特性具有很強(qiáng)的理論價(jià)值與實(shí)際意義�，F(xiàn)有的軟粘土流變固結(jié)研究中較少涉及軟土微觀特性和形態(tài)對軟土流變固結(jié)與變形的影響,然而軟土的礦物組成和微觀結(jié)構(gòu)的性質(zhì)對其流變固結(jié)有重要的影響。另外,當(dāng)前關(guān)于流變固結(jié)過程中考慮土體自身應(yīng)力歷史的研究并不多見,理論分析中應(yīng)當(dāng)考慮流變固結(jié)過程中土壓縮性與滲透性參數(shù)非線性變化的性質(zhì)。本文正是遵循這一思路,針對軟粘土的流變固結(jié)問題,分別在微觀與宏觀尺度上開展了試驗(yàn)與理論的研究,嘗試為這一經(jīng)典的土力學(xué)問題提出一些新的觀點(diǎn)和思路。文中主要的工作如下： (1)對寧波濱海粘土開展GDS先進(jìn)固結(jié)儀試驗(yàn),分析研究該類型粘土的非線性壓縮特性和再壓縮特性,對常用的幾種非線性壓縮模型進(jìn)行擬合分析,為非線性流變固結(jié)理論研究提供依據(jù)。對杭州粘土開展微觀尺度試驗(yàn),包括：①應(yīng)用X射線能譜分析測定粘土的元素組成；②采用X射線衍射分析方法對粘土材料進(jìn)行物相分析；③利用掃描電鏡與壓汞試驗(yàn)觀測不同壓力等級下經(jīng)固結(jié)和流變后粘土的微觀形貌特征,測定其孔隙分布規(guī)律及其變化,為微結(jié)構(gòu)力學(xué)模型的建立提供依據(jù)。 (2)在粘土微觀形態(tài)和結(jié)構(gòu)研究的基礎(chǔ)上,提出能描述荷載作用下土體微觀結(jié)構(gòu)變形特性的物理模型。對模型進(jìn)行力學(xué)分析,推導(dǎo)得到宏觀力學(xué)參量與微觀參數(shù)之間的關(guān)系,應(yīng)用非線性突變理論建立軟土的微結(jié)構(gòu)力學(xué)模型和本構(gòu)關(guān)系。模型中涉及土的孔隙分布、微結(jié)構(gòu)變形特性、粘彈性應(yīng)力應(yīng)變關(guān)系等,并采用室內(nèi)土工試驗(yàn)來驗(yàn)證其理論的正確性。 (3)建立考慮軟土應(yīng)力歷史的線性與非線性流變固結(jié)宏觀唯象模型,在此基礎(chǔ)上得到相應(yīng)的流變固結(jié)控制方程,采用半解析方法對其進(jìn)行求解。綜合考量地基土體的應(yīng)力歷史、外部荷載、土的壓縮性、流變性、滲透性、雙層地基土體相對厚度等因素,對考慮應(yīng)力歷史條件下的單層和雙層地基(帶軟弱下臥層)一維線性與非線性流變固結(jié)性狀進(jìn)行分析和研究。 (4)基于Leonards和Bjerrum的研究,分析了土體的老化現(xiàn)象及其發(fā)生的機(jī)理。針對準(zhǔn)先期固結(jié)應(yīng)力和“消失”的先期固結(jié)應(yīng)力兩種典型的老化土體的力學(xué)現(xiàn)象,開展了對應(yīng)的非線性流變固結(jié)問題理論研究工作。在四元件流變模型和實(shí)驗(yàn)數(shù)據(jù)擬合得到的參數(shù)模型的基礎(chǔ)上給出了控制方程,利用半解析方法對其求解后分析土體老化對固結(jié)性狀的影響。
[Abstract]:The study of soil mechanical behavior usually has two parallel main lines: macro scale and micro scale. The mechanical behavior of soil on macroscopic scale is determined by the characteristics of particle and structure in microscopic scale. Therefore, it is of great theoretical value and practical significance to apply the microscopic physical test and mechanical analysis to explain the macroscopic mechanical properties of soil in the study of macro scale and micro scale. In the present study of rheological consolidation of soft clay, the influence of microcosmic characteristics and morphology of soft clay on rheological consolidation and deformation of soft clay is seldom discussed. However, the mineral composition and microstructure of soft clay have an important effect on rheological consolidation of soft clay. In addition, there are few researches on the stress history of soil in rheological consolidation process, and the nonlinear variation of soil compressibility and permeability parameters should be considered in theoretical analysis. In this paper, the rheological consolidation of soft clay has been studied on the micro scale and macroscopic scale, and some new ideas and ideas have been put forward for this classical soil mechanics problem. The main work in this paper is as follows: In this paper, the GDS advanced consolidation instrument test is carried out on Ningbo coastal clay. The nonlinear compression characteristics and recompression characteristics of this type of clay are analyzed, and several commonly used nonlinear compression models are fitted and analyzed. It provides a basis for the study of nonlinear rheological consolidation theory. The microscale tests were carried out on the clay in Hangzhou, including the determination of the element composition of the clay by X-ray energy spectrum analysis. The phase analysis of the clay material was carried out by means of X-ray diffraction analysis. (3) scanning electron microscopy (SEM) and mercury injection test were used to observe the microstructure of clay after consolidation and rheology under different pressure levels, and the pore distribution and its changes were measured, which provided the basis for the establishment of microstructural mechanics model. 2) based on the study of the microstructure and structure of clay, a physical model which can describe the deformation characteristics of soil microstructure under load is proposed. The relationship between macroscopic and microscopic parameters is derived by mechanical analysis of the model, and the microstructural mechanics model and constitutive relation of soft soil are established by using nonlinear catastrophe theory. The pore distribution of soil, deformation characteristics of microstructure, viscoelastic stress-strain relationship and so on are involved in the model. Laboratory geotechnical tests are used to verify the correctness of the theory. 3) the macroscopic phenomenological model of linear and nonlinear rheological consolidation considering the stress history of soft soil is established, and the corresponding rheological consolidation control equation is obtained, and the semi-analytical method is used to solve it. The factors such as stress history, external load, compressibility, rheology, permeability, relative thickness of soil on double-layer foundation are comprehensively considered. The one-dimensional linear and nonlinear rheological consolidation behavior of single-layer and double-layer subgrade (with weak underlying layer) under the condition of stress history is analyzed and studied. (4) based on the research of Leonards and Bjerrum, the aging phenomenon of soil and its occurrence mechanism are analyzed. Aiming at the mechanical phenomena of two typical aging soils, the quasi-pre-consolidation stress and the "vanishing" pre-consolidation stress, the corresponding theoretical research on the nonlinear rheological consolidation problem was carried out. On the basis of the four-element rheological model and the parameter model fitted from the experimental data, the governing equation is given. The effect of soil aging on the consolidation behavior is analyzed by semi-analytical method.
【學(xué)位授予單位】：浙江大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2013
【分類號】：TU447

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