本文選題：軟黏土 + 流變性�。� 參考：《暨南大學(xué)》2015年博士論文

【摘要】：軟黏土廣泛分布在我國沿海、沿江等經(jīng)濟(jì)發(fā)達(dá)地區(qū),其具有含水率高、孔隙比大、壓縮性強(qiáng)、黏滯性等特點(diǎn),這使得在軟黏土地基上修筑結(jié)構(gòu)物時(shí),其沉降問題尤其是長期沉降問題就顯得尤為突出。軟黏土的變形過程與時(shí)間密切相關(guān),這既包括超靜孔隙水壓力消散、土體體積壓密的固結(jié)過程,還包括由于其黏滯特性所引起的蠕變變形,兩者互相影響,共同決定著土體的長期沉降。因此,如何基于土體變形的時(shí)間效應(yīng),建立起可以反映軟黏土蠕變特性的本構(gòu)模型并實(shí)現(xiàn)蠕變-固結(jié)的耦合作用,是工程界和學(xué)術(shù)界共同探討的熱點(diǎn)問題。本研究使用室內(nèi)試驗(yàn)、理論分析及數(shù)值模擬等方法對軟黏土的固結(jié)、蠕變特性及控制方程的建立進(jìn)行了綜合研究,主要研究內(nèi)容及成果如下:(1)開展了一維K0側(cè)限固結(jié)試驗(yàn)、三軸固結(jié)不排水剪切試驗(yàn)、三軸固結(jié)不排水蠕變試驗(yàn),分析了軟黏土變形的時(shí)效性特征和變形機(jī)理,并為進(jìn)一步彈黏塑性本構(gòu)模型的建立提供了試驗(yàn)基礎(chǔ)。試驗(yàn)成果表明:1)土體的次固結(jié)系數(shù)隨著加載時(shí)間的增長及預(yù)壓作用而減小;且次固結(jié)系數(shù)隨荷載的增加而增大,但其增加幅度依賴于土體的固結(jié)狀態(tài),次固結(jié)系數(shù)隨荷載變化曲線會在與pc有關(guān)的某一范圍處出現(xiàn)轉(zhuǎn)折點(diǎn)。次固結(jié)系數(shù)與壓縮指數(shù)之間呈較好的線性關(guān)系,其比值在0.028~0.049之間。2)當(dāng)上部荷載較小時(shí),土體的三軸固結(jié)不排水蠕變變形隨時(shí)間會逐漸減弱并最終趨于穩(wěn)定;而當(dāng)荷載達(dá)到一臨界強(qiáng)度時(shí),土體的蠕變變形會在加載一段時(shí)間后隨時(shí)間快速發(fā)展,土體發(fā)生剪切蠕變破壞。3)在應(yīng)變控制模式下,土體的不排水剪切強(qiáng)度會隨著剪切應(yīng)變速率的提高而增加,且其率相關(guān)性可以很好地用速率參數(shù)表征。(2)基于一維K0側(cè)限固結(jié)試驗(yàn)的成果,在Bjerrum等時(shí)間線理論的基礎(chǔ)上驗(yàn)證了將蠕變變形當(dāng)作與時(shí)間相關(guān)塑性變形這一假設(shè)的合理性,并分別從蠕變效應(yīng)及應(yīng)變率效應(yīng)兩個(gè)角度推導(dǎo)了一維K0側(cè)限條件下的非線性彈黏塑性模型,給出了模型參數(shù)的物理意義及獲取方法。將所建立的非線性彈黏塑性模型引入一維Terzaghi固結(jié)理論,建立了一維K0側(cè)限條件下的蠕變固結(jié)耦合控制方程,并通過Crank Nicolson有限差分格式對控制方程進(jìn)行了求解。通過對一維K0側(cè)限固結(jié)試驗(yàn)的模擬及與Imai和Leroueil的試驗(yàn)結(jié)果對比,驗(yàn)證了所建模型的合理性。計(jì)算結(jié)果表明,隨著土樣高度的增加、土體黏滯特性的增強(qiáng),本文模型與假設(shè)A計(jì)算所得的主固結(jié)完成時(shí)的變形量之間的差值也會越來越大。(3)基于改進(jìn)的GJY型K0固結(jié)儀開展了一維柔性等比側(cè)限固結(jié)試驗(yàn),分析了土體在允許一定側(cè)向變形時(shí)的壓縮特性,并將試驗(yàn)結(jié)果與K0側(cè)限條件下的成果進(jìn)行了對比分析。結(jié)果表明,柔性等比側(cè)限條件下的壓縮曲線、壓縮指數(shù)及次固結(jié)系數(shù)的發(fā)展規(guī)律均與K0側(cè)限條件下的一致,但由于側(cè)向變形的產(chǎn)生,其壓縮指數(shù)約為K0側(cè)限條件下的1.08~1.16倍,次固結(jié)系數(shù)約為K0側(cè)限條件下的1.1~1.3倍。在柔性等比側(cè)限固結(jié)試驗(yàn)的基礎(chǔ)上,根據(jù)達(dá)西定律、有效應(yīng)力原理及連續(xù)性原理推導(dǎo)出柔性等比側(cè)限條件下的一維固結(jié)方程,且與建立的非線性彈黏塑性模型進(jìn)行耦合,得到柔性等比側(cè)限條件下的蠕變固結(jié)耦合控制方程,并給出了模型參數(shù)的意義及確定方法。通過對柔性等比側(cè)限壓縮試驗(yàn)結(jié)果的模擬,驗(yàn)證了模型的合理性,且模擬結(jié)果表明,柔性等比側(cè)限條件下土樣厚度、次固結(jié)系數(shù)對主固結(jié)完成時(shí)應(yīng)變值的影響均較K0側(cè)限條件下的大,本文對單層地基在柔性等比側(cè)限條件下計(jì)算所得的主固結(jié)完成時(shí)的應(yīng)變值約為K0側(cè)限條件下的1.17倍。(4)為拓寬蠕變固結(jié)共同作用的路徑,本文還基于室內(nèi)蠕變試驗(yàn)成果建立了含分?jǐn)?shù)階導(dǎo)數(shù)的Merchant經(jīng)驗(yàn)?zāi)Ｐ?并對一維K0側(cè)限固結(jié)試驗(yàn)及三軸固結(jié)不排水蠕變試驗(yàn)成果進(jìn)行了擬合,給出了模型參數(shù)的取值范圍。該模型可以回避蠕變固結(jié)相互作用的復(fù)雜機(jī)理,從宏觀上預(yù)測實(shí)際工程的長期變形。計(jì)算結(jié)果表明,與傳統(tǒng)的Merchant模型相比,分?jǐn)?shù)階導(dǎo)數(shù)Merchant模型能更好地描述軟黏土的蠕變變形,尤其是對于模擬試驗(yàn)曲線拐點(diǎn)處的變形具有明顯優(yōu)勢,且能更好地反映土體變形隨時(shí)間發(fā)展的非線性化程度。模型參數(shù)分析表明,在各級荷載作用下階數(shù)α的變化范圍最小,而黏滯性系數(shù)η1的變化范圍最大,但從精度上總的來說可以滿足工程計(jì)算的要求。(5)基于Perzyna過應(yīng)力理論,引入?yún)⒖济娴母拍罱⒘艘话銘?yīng)力條件下的三維非線性彈黏塑性模型,并考慮了初始各向異性的影響。通過將所建立的本構(gòu)模型引入至Biot固結(jié)理論,實(shí)現(xiàn)了三維條件下的蠕變固結(jié)耦合,并推導(dǎo)出了應(yīng)力增量及增量形式的雅克比矩陣的表達(dá)式,編制了Abaqus有限元軟件中的UMAT子程序,對軟基上堆載問題進(jìn)行了模擬。計(jì)算結(jié)果表明,由于土體的蠕變作用,即使外荷載保持不變,當(dāng)排水條件較差時(shí),孔隙水壓力隨時(shí)間也會有一定幅度的增加,并對地基的變形和長期變形產(chǎn)生實(shí)際影響。
[Abstract]:Soft clay is widely distributed in the coastal areas of China, along the river and other economically developed areas. It has the characteristics of high water content, large pore ratio, strong compressibility, viscosity and so on. This makes the settlement problem especially the long-term settlement especially when the structure is built on the soft clay foundation. The deformation process of soft clay is closely related to the time, which is not only closely related to the time of the soft clay. The consolidation process including the dissipation of excess pore water pressure and the consolidation process of soil volume compaction, including the creep deformation caused by its viscosity, both influence each other and determine the long-term settlement of soil. Therefore, based on the time effect of soil deformation, the constitutive model which can reflect the creep properties of soft clay is established and the creep is realized. The coupling effect of consolidation is a hot issue in the engineering and academic circles. This study uses laboratory tests, theoretical analysis and numerical simulation to study the consolidation of soft clay, the creep properties and the establishment of the control equation. The main research contents and results are as follows: (1) one dimension K0 side limit consolidation test and three axis are carried out. The consolidation undrained shear test, the three axis consolidation undrained creep test, analyzed the aging characteristics and deformation mechanism of the soft clay deformation, and provided an experimental basis for the establishment of further elastoplastic constitutive model. The test results showed that the secondary consolidation coefficient of soil decreased with the increase of loading time and preloading, and secondary consolidation. The coefficient increases with the increase of load, but its increase depends on the consolidation state of the soil. The secondary consolidation coefficient appears to be a turning point at a certain range related to the PC. The coefficient of secondary consolidation has a good linear relationship with the compression index, and its ratio is.2 between 0.028~ 0.049) when the upper load is smaller, the soil mass is lower. The undrained creep deformation of three axis will gradually weaken with time and eventually tends to stability, and when the load reaches a critical strength, the creep deformation of the soil will develop quickly after loading for a period of time, and the soil has shear creep failure.3). Under the strain control mode, the undrained shear strength of soil will change with the shear strain. The rate correlation can be increased and its rate correlation can be well characterized by rate parameters. (2) based on the results of one dimensional K0 side limit consolidation test, the rationality of the creep deformation as a time dependent plastic deformation hypothesis is verified on the basis of the Bjerrum equal time line theory, and the creep and strain rate effects are from the angle of creep and strain rate respectively. The nonlinear elastic viscoplastic model of one dimension K0 side limit is derived, the physical meaning and the method of obtaining the model parameters are given. The nonlinear elastic viscoplastic model is introduced into the one-dimensional Terzaghi consolidation theory, and the coupling control equation of the creep consolidation under the one dimension K0 side limit is established, and the finite difference scheme of the Crank Nicolson is adopted. Through the simulation of the one-dimensional K0 side limit consolidation test and the comparison with the experimental results of Imai and Leroueil, the rationality of the model is verified. The calculation results show that the viscosity of the soil increases with the increase of the height of the soil sample, and the deformation amount of the model and the false A are calculated by the model and the false A. The difference between them is also getting bigger and bigger. (3) based on the improved GJY K0 consolidation instrument, a one-dimensional flexible equal side limit consolidation test is carried out. The compression characteristics of the soil in a certain lateral deformation are analyzed, and the experimental results are compared with the results under the K0 side limit. The development law of the compression index and the secondary consolidation coefficient are all consistent with the K0 side limit, but because of the lateral deformation, the compression index is about 1.08~1.16 times of the K0 side limit and the secondary consolidation coefficient is about 1.1~1.3 times of the K0 side limit. On the basis of the flexible equal side limit consolidation test, the effective stress principle is based on Darcy's law. And the continuity principle is used to derive the one-dimensional consolidation equation under the flexible equivalent side limit condition, and coupled with the nonlinear elastoviscoplastic model established, the coupling control equation of the creep consolidation under the flexible isometric side limit is obtained, and the significance and the determination method of the model parameters are given. The model is proved to be reasonable, and the simulation results show that the influence of the soil sample thickness and the secondary consolidation coefficient on the strain value at the completion of the main consolidation is larger than that under the K0 side limit condition. In this paper, the strain value of the single layer foundation under the flexible equivalent side limit condition is about K0 side limit under the condition of the main consolidation. 1.17 times. (4) in order to widen the path of the common action of creep consolidation, based on the laboratory creep test results, the Merchant empirical model with fractional derivative is established, and the one-dimensional K0 side limit consolidation test and the three axis consolidation undrained creep test results are fitted, and the range of the model parameters is given. This model can avoid vermicular creep. The complex mechanism of the consolidation interaction is used to predict the long-term deformation of the actual project from the macroscopic point of view. The calculation results show that the fractional derivative Merchant model can better describe the creep deformation of the soft clay compared with the traditional Merchant model, especially for the deformation at the turning point of the simulated test curve, and it can be better reflected. The nonlinear degree of soil deformation developed with time. The model parameter analysis shows that the variation range of the order number alpha is the least, and the viscosity coefficient ETA 1 has the largest variation range, but it can meet the requirements of engineering calculation in general. (5) based on the theory of Perzyna over stress, the concept of reference surface is introduced. The three-dimensional nonlinear elastic viscoplastic model under the general stress condition and the effect of initial anisotropy are taken into account. By introducing the established constitutive model to the Biot consolidation theory, the coupling of creep consolidation under three dimensional conditions is realized, and the expression of the Jacobi matrix of stress increment and incremental form is derived, and the finite Abaqus is drawn up. The UMAT subroutine in the meta software is used to simulate the loading problem on the soft foundation. The calculation results show that the pore water pressure increases with time, and the deformation and long-term deformation of the foundation can be influenced by the creep of the soil.

【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TU447

【參考文獻(xiàn)】

相關(guān)期刊論文 前10條

1 陳建峰,秦建慶,石振明,沈明榮;砂井地基沉降的二維有限元分析(一)——三維問題轉(zhuǎn)換為二維平面應(yīng)變問題[J];四川建筑科學(xué)研究;2003年03期

2 柳文濤;曹得占;李惠;趙傳海;;深圳海相沉積軟土蠕變特性的試驗(yàn)研究[J];工業(yè)建筑;2011年07期

3 陳波;胡云世;張效忠;田芳;王寶峰;;上海軟黏土壓縮特性的試驗(yàn)研究[J];工程勘察;2014年09期

4 蔣明鏡;劉靜德;尹振宇;;Consolidation and Creep Behaviors of Two Typical Marine Clays in China[J];China Ocean Engineering;2014年05期

5 周宏偉;王春萍;段志強(qiáng);張淼;劉建鋒;;基于分?jǐn)?shù)階導(dǎo)數(shù)的鹽巖流變本構(gòu)模型[J];中國科學(xué):物理學(xué) 力學(xué) 天文學(xué);2012年03期

6 姜晨光;宋艷萍;胡聞;陳江渝;祝付玲;何躍平;夏正興;;太湖第四紀(jì)沉積區(qū)土體荷載響應(yīng)的效應(yīng)綜合特征[J];江南大學(xué)學(xué)報(bào)(自然科學(xué)版);2012年01期

7 王志玲，張印杰;剪切速率對擊實(shí)粘土強(qiáng)度特性影響的試驗(yàn)研究[J];人民黃河;1996年05期

8 徐志英;;考慮到土骨架蠕變的三向固}P理娭[J];水利學(xué)報(bào);1964年04期

9 趙維炳,陳永輝,龔友平;平面應(yīng)變有限元分析中砂井的處理方法[J];水利學(xué)報(bào);1998年06期

10 陳宗基;固結(jié)及次時(shí)間效應(yīng)的單向問題[J];土木工程學(xué)報(bào);1958年01期

相關(guān)博士學(xué)位論文 前4條

1 楊愛武;結(jié)構(gòu)性吹填軟土流變特性及其本構(gòu)模型研究[D];天津大學(xué);2011年

2 張超杰;結(jié)構(gòu)性軟土一維彈粘塑性固結(jié)性狀研究[D];浙江大學(xué);2003年

3 劉用海;寧波軟土工程特性及其本構(gòu)模型應(yīng)用研究[D];浙江大學(xué);2008年

4 但漢波;天然軟粘土的流變特性[D];浙江大學(xué);2009年

相關(guān)碩士學(xué)位論文 前1條

1 朱鴻鵠;軟土固結(jié)—蠕變耦合效應(yīng)的試驗(yàn)研究及有限元分析[D];暨南大學(xué);2005年

，

本文編號：1775200