本文選題：擋土墻　切入點(diǎn)：土壓力　出處：《北京建筑大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

【摘要】：大量的模型試驗和現(xiàn)場實測數(shù)據(jù)均表明,擋土墻后土壓力沿墻高呈非線性分布,并非經(jīng)典土壓力給出的線性分布假設(shè)。眾多巖土工作者已經(jīng)對土壓力非線性分布現(xiàn)象達(dá)成了共識,并且提出了很多理論來解釋這種現(xiàn)象。其中最著名的是卡崗在經(jīng)典庫倫理論的基礎(chǔ)上提出的以水平條形單元為研究對象的水平層分析法。但是這種方法給出的只是墻后土壓力拋物線形狀的分布,更不能解釋土壓力中間狀態(tài)和土體破壞的機(jī)理。更多的模型和實測數(shù)據(jù)也揭示了墻后土壓力沿墻高的非線性分布呈現(xiàn)“R”形或者周期性波動的特點(diǎn),這是現(xiàn)有的土壓力計算理論無法的解釋的。本文試圖聯(lián)系內(nèi)變量梯度理論,利用內(nèi)變量梯度理論在解釋應(yīng)變局部化、應(yīng)力應(yīng)變空間周期分布方面的顯著優(yōu)勢,為土壓力分布的研究提供一個新的思路。本文利用梯度理論研究了土壓力沿墻高分布周期性波動分布現(xiàn)象,取得了如下主要成果:土體作為典型的散體材料,不同于一般的連續(xù)介質(zhì)材料,在力學(xué)行為方面往往表現(xiàn)出非局部特性。經(jīng)典的土壓力理論是建立在傳統(tǒng)彈塑性力學(xué)基礎(chǔ)上,將土作為連續(xù)介質(zhì)進(jìn)行的研究,具有一定得局限性,不能解釋土壓力沿墻高周期性波動分布現(xiàn)象。(1)在經(jīng)典Mohr-Coulomb破壞準(zhǔn)則的基礎(chǔ)上,考慮了一點(diǎn)的應(yīng)力狀態(tài)與相鄰點(diǎn)的應(yīng)變梯度的關(guān)系,用周圍點(diǎn)的應(yīng)力平均值來代替一點(diǎn)的應(yīng)力值。引入應(yīng)力張量第一不變量(靜水壓力)的二階梯度項,利用平面應(yīng)變假設(shè),得到了擋土墻水平土壓力沿墻高分布的解析解,結(jié)果表明該模型能較好的描述擋土墻后土壓力沿墻高的周期性分布;(2)進(jìn)一步討論了內(nèi)稟長度影響主動土壓力分布的規(guī)律。作為表征材料內(nèi)部尺寸而被引入的內(nèi)稟長度,既保證了量綱平衡,也使得土體結(jié)構(gòu)的自我組織和耗散、顆粒之間的長程相互作用的影響被引入到破壞準(zhǔn)則中。墻后土體隨著深度增加會越來越密實,內(nèi)稟尺寸也會越來越大,土壓力周期和波動都會隨之增大;(3)在已經(jīng)得到的內(nèi)變量梯度模型的基礎(chǔ)上,進(jìn)一步考慮到土的應(yīng)力應(yīng)變關(guān)系的下降段,聯(lián)系側(cè)向應(yīng)力-應(yīng)變和土壓力-位移的類似關(guān)系,將擋土墻的位移量引入到方程中去,得到了墻后土壓力隨擋土墻位移變化的分布變化;(4)在研究了平動模式下,擋土墻位移與墻后土體應(yīng)力應(yīng)變關(guān)系后,繼續(xù)考慮擋土墻繞墻底轉(zhuǎn)動(RB模式)和繞墻頂轉(zhuǎn)動(RT模式)兩種最基本的轉(zhuǎn)動模式。利用轉(zhuǎn)動參數(shù)定量地描述了擋土墻的轉(zhuǎn)動狀態(tài),并將參數(shù)引入到內(nèi)變量梯度模型中得到了墻后土壓力在不同轉(zhuǎn)動狀態(tài)下的土壓力分布。內(nèi)變量梯度解聯(lián)系了位移模式與層間等效內(nèi)摩擦角的關(guān)系,能很好的描述擋土墻在轉(zhuǎn)動狀態(tài)下墻后土壓力從主動極限狀態(tài)到被動土壓力狀態(tài)或者過極限破壞狀態(tài)整個過程的變化情況利用改進(jìn)的土壓力計算模型,將彈塑分區(qū)的概念引入到計算模型中去,進(jìn)一步明確墻后土體破裂面形狀和彈塑性分區(qū)形狀,求出彈性區(qū)高度。內(nèi)變量梯度模型中控制系數(shù)的確定吸收了廣大學(xué)者在墻后土體彈塑性分區(qū)的成果,利用彈塑分區(qū)界點(diǎn)處土壓力連續(xù)光滑作為邊界條件。本文也借鑒了前輩學(xué)者在墻后土體彈塑性分區(qū)、土體軟弱下降段、內(nèi)摩擦角逐步發(fā)揮等概念和理論,是對傳統(tǒng)土壓力的繼承和發(fā)展。
[Abstract]:A large number of model experiments and field data show that the earth pressure retaining wall along wall height distribution is nonlinear, the linear distribution assumption is not the classical earth pressure is given. Many geotechnical workers have reached a consensus on the earth pressure distribution of nonlinear phenomena, and put forward many theories to explain this phenomenon. The most famous is the post card based on the classical theory of Kulun on the horizontal bar unit as the research object of the horizontal layer analysis method. But this method gives only the earth pressure behind parabolic shape distribution mechanism not to destroy the earth pressure and explain the intermediate state of soil. More features of the model and field data also reveals the wall earth pressure along the nonlinear the wall height distribution showed the "R" - shaped or cyclical fluctuations, this is not the explanation theory to calculate the earth pressure existing. This article attempts to contact the internal variable Gradient theory, using the theory of variable gradient of strain localization in the interpretation, should be a significant advantage in periodic stress space, provide a new way to study the distribution of earth pressure of earth pressure along wall height distribution of the periodic fluctuation of distribution gradient theory in this paper, the main results are as follows: soil as a typical granular material, different from the continuous medium materials, in mechanical behavior often exhibit non local characteristics. Classical earth pressure theories are based on the traditional elastic-plastic mechanics on the basis of research on the soil as a continuous medium, has certain limitations, cannot explain the earth pressure along the wall of high cycle the fluctuation of distribution. (1) based on the classical Mohr-Coulomb criterion, considering the point of relationship between strain gradient stress and adjacent points, stress points around the mean value generation For a little stress value. The stress tensor invariants (hydrostatic pressure) of the two step, using the plane strain hypothesis analysis of retaining wall horizontal earth pressure distribution along the wall of the solution is obtained. The results show that the model can describe the soil pressure on retaining wall along the periodic distribution of the high walls; (2) further discusses the intrinsic length effect of active earth pressure distribution. The intrinsic length was introduced as an internal size characterization of materials, both to ensure the dimensional balance, but also the structure of the self organization and dissipation, influence between particles and Cheng Xiang interaction is introduced into the failure criterion. After the wall with the increase of the depth of soil will be more dense, the intrinsic size will be more and more, the earth pressure cycle and fluctuation will increase; (3) based on variable gradient model has been on the further consideration of soil stress strain Descending system, lateral contact stress and strain should be similar between the earth pressure and the displacement of the retaining wall, the displacement is introduced into the equation to get the wall soil pressure distribution with change of retaining wall displacement; (4) in the study of translational mode, the stress-strain relation of retaining wall displacement and after the wall, continue to consider retaining wall rotation around the bottom of the wall (RB) and rotation around the top of the wall (RT) of two kinds of the most basic rotation mode. Using the rotation parameters quantitatively describe the rotation state of the retaining wall, and the parameter into the internal variables in the gradient model of the earth pressure on the wall different rotation soil pressure under the condition of variable gradient distribution. Solutions between friction angle and interlayer equivalent displacement model, which can well describe the retaining wall in the rotating wall earth pressure from the active limit state to the passive earth pressure state or ultimate failure The calculation model of soil pressure improved the whole process of using state changes, will play the concept of plastic partition into the calculation model to further clarify the soil behind the wall rupture shape and elastic-plastic shape, calculate the height of the elastic zone. The absorption of the majority of scholars in the wall after the soil elastic-plastic results confirm the control the coefficient of internal variable gradient model, using elastic-plastic soil pressure at the partition point is continuous and smooth as boundary conditions. This paper also draws scholars behind the wall soil elastoplastic soil soft partition, descent stage, internal friction angle gradually play the concept and theory, is the inheritance and development of traditional earth pressure.

【學(xué)位授予單位】：北京建筑大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2017
【分類號】：TU476.4;TU432

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