【摘要】：在眾多類型的支擋結(jié)構(gòu)中,支護(hù)樁因側(cè)向抗力大、施工方便、對周邊地質(zhì)體擾動相對較小等優(yōu)點(diǎn),被廣泛應(yīng)用于各類邊坡治理、基坑支護(hù)工程中。支護(hù)樁是一種水平方向不連續(xù)的支擋結(jié)構(gòu),這種不連續(xù)的目的一方面在于合理利用土體的自承能力;另一方面使其可以有較深的嵌固段,從而將荷載傳遞至相對穩(wěn)定的深部地層中。當(dāng)支護(hù)樁存在臨空段時,如何確保樁間臨空土體的穩(wěn)定性成為工程技術(shù)人員需要解決的問題。國內(nèi)外學(xué)者針對支護(hù)樁等非連續(xù)擋土系統(tǒng)開展了卓有成效的研究,但關(guān)于樁間臨空土體局部破壞現(xiàn)象的研究尚不充分,對樁間臨空土體局部破壞機(jī)理及影響因素的認(rèn)識并不全面,而且缺乏便于工程應(yīng)用的樁間臨空土體穩(wěn)定性分析方法。本文采用理論分析、數(shù)值模擬和振動臺模型試驗(yàn)手段對相鄰兩支護(hù)樁間臨空土體破壞機(jī)理和穩(wěn)定性分析方法展開研究,主要內(nèi)容及成果包括:①從工程案例和模型試驗(yàn)現(xiàn)象入手,歸納出樁間臨空土體的三種破壞模式,并對每種破壞模式的誘發(fā)因素、形成機(jī)制、識別特征、工程應(yīng)對措施進(jìn)行論述,為系統(tǒng)研究樁間臨空土體破壞規(guī)律和機(jī)理、有針對性地建立樁間臨空土體穩(wěn)定性分析方法奠定基礎(chǔ)。②基于力學(xué)分析方法獲得土體中支護(hù)應(yīng)力場的空間分布規(guī)律;根據(jù)支護(hù)作用的發(fā)生機(jī)制和支護(hù)應(yīng)力場的不均勻特性,將被支護(hù)土體分為“直接約束區(qū)”和“間接約束區(qū)”兩部分,從應(yīng)力擴(kuò)散和土拱效應(yīng)的角度研究了“間接約束區(qū)”土體的力學(xué)特征;提出樁間臨空土體潛在局部破壞區(qū)域的界定方法。③在綜合考慮土體應(yīng)變局部化特性和剪切帶擴(kuò)展機(jī)理的基礎(chǔ)上,分析了樁間三維滑動土楔的形成機(jī)制,建立了一種空間滑動楔形體模型;提出樁間臨空土體穩(wěn)定性評價(jià)指標(biāo)體系與相應(yīng)的判據(jù);針對樁間臨空土體滑塌失穩(wěn)破壞模式,基于能量平衡原理和極限分析上限定理提出一種能夠考慮地震作用的樁間臨空土體穩(wěn)定性分析方法;采用三維有限差分法結(jié)合強(qiáng)度折減法獲得了樁間臨空土體穩(wěn)定性系數(shù)數(shù)值解。④采用單一變量法研究了樁間臨空面幾何尺寸、被支護(hù)土體強(qiáng)度參數(shù)以及地震作用對樁間臨空土體穩(wěn)定性的影響;對理論計(jì)算結(jié)果和數(shù)值模擬結(jié)果進(jìn)行了詳細(xì)對比,明確了兩種方法的適用范圍。研究發(fā)現(xiàn),樁間臨空土體穩(wěn)定性系數(shù)隨著土體黏聚力、內(nèi)摩擦角的增大而增大;隨著樁間臨空面寬度的增大而降低,但下降的趨勢逐漸變緩;隨著臨空面高度的增大而降低,且降低的趨勢逐漸減緩。當(dāng)臨空面高寬比位于4/1~1/1區(qū)間時,三維理論分析方法得到的臨空土體穩(wěn)定性系數(shù)隨樁間臨空面幾何尺寸、被支護(hù)土體強(qiáng)度參數(shù)的變化規(guī)律與三維有限差分法數(shù)值模擬結(jié)果基本保持一致,且略偏于安全。⑤采用擬靜力法研究了水平地震作用與豎向地震作用對樁間臨空土體穩(wěn)定性的影響。研究發(fā)現(xiàn),水平地震作用與豎向地震作用均會降低樁間臨空土體的穩(wěn)定性;同時考慮水平地震作用與豎向地震作用時求得的樁間臨空土體地震穩(wěn)定性系數(shù)小于單獨(dú)考慮水平地震作用或豎向地震作用時求得的地震穩(wěn)定性系數(shù);不論是樁間臨空面寬度增大或是臨空面高度增大,樁間臨空土體地震屈服加速度系數(shù)均有所降低。⑥考慮到擬靜力法將地震過程用施加在滑動土楔上的慣性力來表征,存在高估或低估地震作用的可能,進(jìn)一步采用小型精密地震模擬振動臺系統(tǒng)和自行開發(fā)的剛性邊界支護(hù)樁模型試驗(yàn)裝置開展了共計(jì)40組破壞性試驗(yàn),探究了樁間臨空土體動力破壞特征,以及臨空面高度、臨空面寬度、土體強(qiáng)度參數(shù)、地震波峰值加速度、加載波形等因素對樁間臨空土體動力破壞性狀的影響,并將試驗(yàn)結(jié)果與理論分析結(jié)果進(jìn)行了對比。
[Abstract]:In many types of retaining structures, retaining piles are widely used in slope treatment because of their large lateral resistance, convenient construction and relatively small disturbance to surrounding geological bodies. On the other hand, it can have a deeper embedded section, so that the load can be transferred to a relatively stable deep stratum. How to ensure the stability of the empty soil between piles becomes a problem that engineers and technicians need to solve. However, the research on the local failure of the soil between piles is still insufficient. The understanding of the mechanism and influencing factors of the local failure of the soil between piles is incomplete, and the stability analysis method of the soil between piles is lacking. In this paper, theoretical analysis, numerical simulation and shaking table model test methods are used. The failure mechanism and stability analysis method of the aerial soil between adjacent two supporting piles are studied. The main contents and achievements include: (1) Starting with engineering cases and model test phenomena, three failure modes of the aerial soil between piles are summarized, and the inducing factors of each failure mode, forming mechanism, identifying characteristics and engineering countermeasures are discussed. In order to systematically study the failure law and mechanism of the soil near the empty between piles, the stability analysis method of the soil near the empty between piles is established. The soil mass is divided into two parts: the direct restraint zone and the indirect restraint zone. The mechanical characteristics of the soil mass in the indirect restraint zone are studied from the point of stress diffusion and soil arching effect. On the basis of the analysis of the formation mechanism of the three-dimensional sliding soil wedge between piles, a spatial sliding wedge model is established, and the evaluation index system and corresponding criteria for the stability of the soil in the air between piles are proposed. In this paper, the stability analysis method of the soil between piles is used, and the numerical solution of the stability coefficient of the soil between piles is obtained by using the three-dimensional finite difference method and the strength reduction method. It is found that the coefficient of stability increases with the increase of soil cohesion and internal friction angle, decreases with the increase of the width of the free surface between piles, but the decreasing trend gradually slows down with the increase of the height of the free surface between piles. When the ratio of height to width is in the range of 4/1~1/1, the stability coefficient of the soil near the empty surface obtained by the three-dimensional theoretical analysis method is in accordance with the geometric size of the empty surface between piles, and the variation law of the strength parameters of the retained soil is basically consistent with the numerical simulation results of the three-dimensional finite difference method, and is slightly safe. Quasi-static method is used to study the influence of horizontal and vertical seismic action on the stability of the soil near the pile space.It is found that both horizontal and vertical seismic action can reduce the stability of the soil near the pile space. The qualitative coefficient is smaller than the seismic stability coefficient obtained when the horizontal or vertical seismic action is considered alone; the seismic yield acceleration coefficient of the empty soil between piles decreases with the increase of the width of the empty surface or the height of the empty surface. Inertia force indicates that there is the possibility of overestimating or underestimating earthquake action. A total of 40 groups of destructive tests were carried out by using a small precision shaking table system and a self-developed rigid boundary supporting pile model test device. The characteristics of dynamic failure of the soil near the pile, as well as the height, width and width of the soil near the pile, were investigated. The influence of strength parameters, peak acceleration of seismic wave, loading waveform and other factors on the dynamic destructive behavior of aerial soil between piles is studied. The experimental results are compared with the theoretical results.
【學(xué)位授予單位】：重慶大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TU473.1

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