發(fā)布時(shí)間：2018-03-03 09:51

  本文選題：黃土　切入點(diǎn)：三軸蠕變?cè)囼?yàn)　出處：《西北農(nóng)林科技大學(xué)》2015年碩士論文　論文類型：學(xué)位論文

【摘要】：隨著西部大開(kāi)發(fā)的進(jìn)行,被廣泛作為基礎(chǔ)工程建設(shè)的建筑材料、建筑環(huán)境和載體的黃土,其變形、強(qiáng)度與穩(wěn)定性隨時(shí)間變化的流變問(wèn)題變得很明顯。實(shí)踐證明,許多工程的破壞與失穩(wěn)問(wèn)題,如自然邊坡和人工邊坡的破壞與失穩(wěn)、基坑開(kāi)挖臨空面的緩慢側(cè)向位移、地基以及路基的緩慢豎向位移、土石壩的變形與失穩(wěn)、隧道施工及運(yùn)營(yíng)時(shí)的地表沉降和變形等問(wèn)題,在大多數(shù)情況下并不是在開(kāi)挖后形成或者工程完工后立即發(fā)生的,而是其中土體的應(yīng)力和變形隨著時(shí)間的推移不斷地調(diào)整、變化和發(fā)展導(dǎo)致的。因此,仍需進(jìn)一步全面深入研究黃土的蠕變特性,以期更加豐富和完善黃土蠕變理論,為具體實(shí)際工程的設(shè)計(jì)、施工與穩(wěn)定性分析提供一定的指導(dǎo)作用,對(duì)保證黃土高原地區(qū)建筑體的長(zhǎng)期安全和正常使用等方面,具有重要的理論和實(shí)踐意義�；趯�(duì)前人黃土三軸蠕變特性研究成果的總結(jié)與思考,本文將進(jìn)一步利用SR-6型三聯(lián)式三軸蠕變儀對(duì)陜西省涇陽(yáng)縣某邊坡Q3黃土原狀樣和重塑樣進(jìn)行三軸固結(jié)排水蠕變?cè)囼?yàn)研究,著重探討含水率、圍壓、偏應(yīng)力水平、應(yīng)力路徑、初始主應(yīng)力角以及其耦合作用對(duì)蠕變特性的影響,并對(duì)試驗(yàn)結(jié)果進(jìn)行整理分析,建立適合該地區(qū)黃土的蠕變模型,本文主要研究成果如下:(1)該地區(qū)黃土具有明顯的蠕變特性,重塑樣呈非線性衰減蠕變特性,而原狀樣呈線性衰減蠕變特性。土樣蠕變變形量的大小受偏應(yīng)力水平、圍壓以及含水率的影響顯著,土樣在高偏應(yīng)力水平、小圍壓、大含水率的條件下蠕變現(xiàn)象明顯且蠕應(yīng)變較大。(2)不同應(yīng)力路徑下重塑黃土的蠕變規(guī)律一致,而在各級(jí)偏應(yīng)力水平下,蠕變變形量差別明顯。過(guò)量加載后卸載試樣的蠕變變形值最大,分級(jí)加載試樣的蠕變變形次之,分別加載試樣的蠕變變形最小。(3)由于分級(jí)荷載的非線性累積后效影響,使得Boltzmann線性疊加法和陳氏法兩種方法處理實(shí)測(cè)數(shù)據(jù)所得結(jié)果有所差別,針對(duì)分級(jí)加載非線性蠕變應(yīng)盡可能使用陳氏法來(lái)處理數(shù)據(jù)。基于數(shù)理統(tǒng)計(jì)的方法,依據(jù)試驗(yàn)資料建立了適合描述該地區(qū)90%壓實(shí)度重塑黃土在20%~65%偏應(yīng)力水平下非線性衰減蠕變特性的兩種經(jīng)驗(yàn)蠕變模型,二者各具優(yōu)點(diǎn),在實(shí)際應(yīng)用中應(yīng)綜合考慮,以期達(dá)到互相驗(yàn)證的效果。(4)利用分級(jí)增量循環(huán)加載方式對(duì)原狀黃土粘彈塑性基本規(guī)律的分析可知,加載時(shí)原狀土樣所產(chǎn)生的蠕應(yīng)變由瞬時(shí)彈性變形、瞬時(shí)塑性變形、粘彈性變形和粘塑性變形四部分組成。卸載后,原狀土樣產(chǎn)生衰減粘彈性回彈變形,回彈量隨著卸荷量的減小,圍壓的增大,含水率的增大而減小。但由于該地區(qū)原狀黃土膠結(jié)強(qiáng)度較弱以及內(nèi)部存在不均勻大孔隙,在較低的應(yīng)力水平下便表現(xiàn)出較強(qiáng)的塑性變形特性,回彈變形不明顯,蠕變過(guò)程中的粘彈性變形在蠕應(yīng)變中所占比重較小。加卸荷應(yīng)力歷史對(duì)黃土的蠕變變形具有累積效應(yīng),將會(huì)加大土體的蠕變變形。依據(jù)試驗(yàn)資料建立了可以較好地描述該地區(qū)原狀黃土的三軸線性衰減蠕變特性粘彈塑性9元件蠕變模型,物理意義明確,且模型參數(shù)可由Origin軟件擬合得到。(5)不同初始主應(yīng)力角的原狀土樣蠕變規(guī)律一致,當(dāng)軸向偏應(yīng)力較小時(shí),初始主應(yīng)力角對(duì)土體的蠕變特性有一定的影響,任意時(shí)刻,軸向蠕變變形隨著初始主應(yīng)力角的增大而增大,由于該地區(qū)黃土的結(jié)構(gòu)性不明顯,總體差別不大。隨著軸向偏應(yīng)力的增大,致使土樣的原生結(jié)構(gòu)被壓壞,土樣本身不再具有結(jié)構(gòu)各向異性,對(duì)于不同初始主應(yīng)力角的土樣,其蠕變變形差別減小,且其大小關(guān)系沒(méi)有一定的規(guī)律性。
[Abstract]:With the great development of Western China, is widely used as a basis for the construction of the building materials, construction environment and the carrier of loess, its deformation, rheological strength and stability with the change of time become apparent. In practice, many engineering damage and instability problems, such as natural slope and artificial slope failure and instability the excavation of free face, slow lateral displacement, foundation and subgrade slow vertical displacement, deformation of embankment dam and instability, the problem of ground tunnel construction and operation of the settlement and deformation, in most cases is not formed after excavation occurs immediately or after the completion of the project, but the soil stress and deformation with the passage of time is adjusted continuously, the change and development of the cause. Therefore, still need further in-depth study on creep characteristics of loess, in order to enrich and perfect the Loess creep theory for The specific design of practical engineering, the analysis provides some guidance for construction and stability, to ensure the Loess Plateau building long-term safety and normal use, which has important theoretical and practical significance. The summary and thinking of the previous Huang Tusan axial creep characteristics based on research results, this paper will further make use of the three axis creep instrument type SR-6 the triple type experiment on consolidation creep three axis to Jingyang County of Shaanxi province Q3 loess slope undisturbed and remolded samples, focusing on the moisture content, confining pressure and deviatoric stress level, stress path, the initial principal stress angle and the coupling effects on creep properties, and the test results are sorted analysis of creep model is established for the loess area, the main results are as follows: (1) the area of loess has obvious creep properties, the rebuilding is nonlinear creep and attenuation characteristics of undisturbed A kind of linear attenuation creep characteristics. The amount of creep deformation is affected by the deviatoric stress level, confining pressure and the influence of moisture content significantly, soil samples under high deviatoric stress level, low confining pressure, creep phenomenon of high moisture conditions and the creep strain significantly larger. (2) under different stress paths consistent heavy plastic loess creep law, and at all levels of deviatoric stress, creep deformation is obviously different. Excessive loading unloading creep deformation value of the specimen, the deformation of the specimen creep loading times, respectively. The minimum creep loading deformation of the specimen (3) due to the cumulative load after effect of nonlinear classification, the Boltzmann linear superposition method and Chen's method two methods of processing the measured data the results vary, according to the classification of load nonlinear creep should as far as possible to use Chen's method to process the data. Based on mathematical statistic method, on the basis of the experimental data was established. He described the area 90% degree of compaction loess in 20%~65% should be two kinds of partial empirical creep model nonlinear stress attenuation creep characteristics, two have their own advantages, should be considered in practical application, in order to verify the effect of each other. (4) analysis by using multi-step incremental cycling loading method on undisturbed loess viscoelastic plastic the basic rule that generated undisturbed loading creep strain by instantaneous instantaneous elastic deformation, plastic deformation, visco elastic and visco plastic deformation of four parts. After unloading, undisturbed attenuation of viscoelastic rebound deformation, the springback decreases with unloading confining pressure increases, the increase of the water content decreases. But because the area of loess and weak cementation strength within the inhomogeneous pore, at low stress level will show the characteristics of strong plastic deformation, the springback deformation is not obvious, creep Viscoelasticity deformation in the process of a smaller proportion in the creep strain. Loading and unloading of loess creep deformation history has a cumulative effect, will increase the creep deformation of soil. According to the test data set up can be used to describe the three axis linear loess attenuation creep characteristics of visco elastic plastic element 9 creep model, clear physical meaning, and the model parameters can be obtained by using the Origin software. (5) different initial principal stress consistent undisturbed creep force angle, axial deviatoric stress is small, the initial principal stress to a certain extent, the creep characteristics of angle on the soil at any time, the axial creep deformation increase with the initial angle of principal stress, because the area of structural loess is not obvious, is not very different. With the increase of axial deviatoric stress, resulting in the primary structure of soil samples were crushed, the soil itself is no longer with the structure To the opposite sex, the creep deformation of soil samples with different initial main stress angles is reduced, and the relation between their size and size is not regular.

【學(xué)位授予單位】：西北農(nóng)林科技大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：TU411

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本文編號(hào)：1560527