本文選題：拉拔試驗　切入點：筋-土界面特性　出處：《暨南大學(xué)》2014年碩士論文　論文類型：學(xué)位論文

【摘要】：軟基上筑堤最棘手的問題便是軟基處理和工期的矛盾，實踐證明，土工織物加筋墊層聯(lián)合豎向排水體處置軟基路堤是行之有效的措施。開展筋-土界面特性研究是進(jìn)行加筋結(jié)構(gòu)設(shè)計、變形與穩(wěn)定性分析的前期基礎(chǔ)性工作，其中界面強(qiáng)度參數(shù)是最關(guān)鍵的技術(shù)指標(biāo)。合理的計算方法及工程實踐有賴于對加筋機(jī)理的認(rèn)識，加筋墊層處置軟基路堤的機(jī)理仍需進(jìn)一步研究。傳統(tǒng)極限平衡法存在明顯的不合理性及保守性，考慮加筋機(jī)理的改進(jìn)模型亟待提出。本文通過開展大量的室內(nèi)試驗和數(shù)值模擬工作研究了砂土強(qiáng)度特性、砂-筋界面特性以及軟基上加筋路堤的加筋機(jī)理，并結(jié)合相關(guān)機(jī)理建立了改進(jìn)的整體穩(wěn)定計算模型，主要研究內(nèi)容和成果如下： （1）砂土強(qiáng)度特性及筋土界面特性研究。利用常規(guī)直剪試驗研究了填筑密度、剪切速率對砂土強(qiáng)度特性的影響。利用拉拔試驗重點研究了拉拔速率對筋-土界面特性的影響規(guī)律和機(jī)理，對比了不同填料界面、筋材類型的加筋效果，討論了內(nèi)摩擦參數(shù)的選取。結(jié)果表明：密度越大，砂土應(yīng)變軟化現(xiàn)象越明顯，而剪切速率對砂土強(qiáng)度特性基本無影響。砂-筋界面應(yīng)力應(yīng)變關(guān)系呈硬化型。界面特性受拉拔速率和法向應(yīng)力的共同影響，其中拉拔速率的影響比較顯著，與試驗方法、填料性質(zhì)和筋材類型等因素有關(guān)。試驗結(jié)果同時表明，試驗速率影響的是嵌鎖、咬合、粘結(jié)作用，對摩擦作用基本無影響。與砂土試驗結(jié)果相比，可知雖然砂-筋界面摩擦角小于填料本身摩擦角，但當(dāng)存在較大界面“似黏聚力”時，界面抗剪強(qiáng)度在一定法向應(yīng)力下可高于砂土。所以，進(jìn)行加筋設(shè)計時須根據(jù)界面“似黏聚力”大小合理選擇內(nèi)摩擦參數(shù)。 （2）基于筋-土界面特性的軟基上加筋路堤變形與穩(wěn)定性分析。采用有限元法對一典型軟基路堤填筑過程進(jìn)行了彈塑性固結(jié)分析，從應(yīng)力應(yīng)變場、筋材拉力和穩(wěn)定性等角度考察了軟基路堤填筑的變形發(fā)展規(guī)律和加筋墊層加固軟基路堤的作用機(jī)理，，并對比了考慮大變形效應(yīng)的計算結(jié)果，探討了界面強(qiáng)度、填筑速度和考慮間接影響帶機(jī)理對計算結(jié)果的影響。結(jié)果表明：加筋能有效約束地基軟土的剪切變形進(jìn)而約束路堤側(cè)向變形，并提高其在固結(jié)階段水平位移的“回籠”能力，能有效降低填筑階段的路堤中心沉降量（但在降低最終沉降量方面不明顯），并使最大豎向位移擴(kuò)展至路堤中心。由于筋-土界面剪應(yīng)力的存在，填筑階段淺層地基土的超靜孔壓較無筋路堤明顯上升，但隨著固結(jié)逐步趨于一致。加筋后路堤的安全系數(shù)有明顯提升，破壞模式發(fā)生改變，改變特征與筋材抗拉強(qiáng)度、界面強(qiáng)度以及地質(zhì)條件等因素有關(guān)�？紤]大變形特征后得到中心軸處沉降和坡腳水平位移較小變形結(jié)果均有明顯降低。界面強(qiáng)度對界面剪應(yīng)力水平和穩(wěn)定性有影響，但對加筋路堤的總變形場及筋材拉力基本無影響。填筑速度對無筋路堤有顯著影響，而加筋路堤則可快速填至預(yù)定高度�？紤]間接影響帶機(jī)理后筋材拉力及界面剪應(yīng)力水平大幅度降低，路堤穩(wěn)定性得到提高。 （3）基于極限平衡條件的軟基上加筋路堤的穩(wěn)定性分析。在傳統(tǒng)分析方法的基礎(chǔ)上結(jié)合間接影響帶機(jī)理建立了改進(jìn)的加筋路堤整體穩(wěn)定計算模型，對軟基上加筋路堤進(jìn)行了不同計算方法下的穩(wěn)定性分析。結(jié)果表明：基于間接影響帶機(jī)理的強(qiáng)度折減法和簡化Bishop法可以體現(xiàn)加筋的作用。強(qiáng)度折減法與簡化Bishop法有很好的一致性，而瑞典條分法的結(jié)果與之有明顯差距，安全系數(shù)偏低且滑弧可信度不高。強(qiáng)度折減法與簡化Bishop法更適合分析加筋對穩(wěn)定性的貢獻(xiàn)。
[Abstract]:On the soft foundation of embankment and the most difficult question is contradiction, soft foundation treatment and construction of practice has proved that the geotextile reinforced cushion with vertical drainage body disposal of embankment on soft ground are effective measures. To carry out the research on reinforcement soil interface properties is the design of the reinforced structure, pre deformation and stability analysis of the foundation work among them, the interface strength parameters are the key index. The calculation method is reasonable and practical depends on the understanding of the mechanism of reinforcement, mechanism of geosynthetic reinforced embankment on soft foundation disposal still needs further study. The traditional limit equilibrium method is not reasonable and conservative obviously, to put forward the improvement model considering the reinforcement mechanism this paper studies the strength characteristics of sand. Through laboratory experiment and numerical simulation of a lot of work, the mechanism of reinforced sand bars and the interface properties of reinforced embankment on soft foundation, and the establishment of the related mechanism The main contents and results of the improved overall stability calculation model are as follows:
(1) study on interfacial properties of strength characteristics of reinforced soil and sand. Using the conventional direct shear test on the filling density, the effects of shear rate on the strength characteristics of sand. The influence law and mechanism of drawing speed on the interface characteristics of reinforced soil pull-out test was used to compare different fillers on interface, the effect of reinforcement reinforcement type the discussion on how to select the internal friction parameters. The results show that the density and sand strain softening phenomenon is more obvious, and the shear rate on the strength characteristics of sand - sand bars. No effect interface stress-strain relationship is hardening. Interface characteristics by drawing rate and method to the common effect of stress, the effect of drawing the rate is significant, and the test method, the property of filling and reinforcement type and other factors. The experimental results also showed that the test rate is on the impact of interlocking, occlusion, bonding, this has no effect on the friction between the base and the sand. Compared with the soil test results, although the sand bar interface friction angle is less than the friction angle of filler itself, but when there is a "quasi cohesion interface", strength in a certain normal stress can be higher than that of the sand soil interface shear. Therefore, reinforcement design should be selected according to the interface "quasi cohesion" size the internal friction parameters.
(2) reinforced embankment on soft foundation reinforcement soil interface properties on the deformation and stability analysis. Based on the analysis of elastoplastic consolidation of a typical soft embankment process by finite element method, the stress and strain field, reinforcement tension and stability of the perspective of the mechanism of deformation of soft soil foundation development law embankment and reinforced by soft base embankment, and compared the calculation results considering large deformation, discusses the interface strength, filling speed and considering the indirect effect mechanism of effect on the calculation results. The results show that the reinforcement can constrain the lateral deformation of embankment and shear deformation of soft soil foundation and effective constraints, and increase in the consolidation stage of horizontal displacement of the "return" of ability, can effectively reduce the filling stage of the embankment settlement center (but the decrease in the final settlement is not obvious), and the maximum vertical displacement of embankment by the extended to the center. In the reinforcement soil interface shear stress exists during construction of the shallow layer soil pore pressure of reinforced embankment increased significantly, but with the gradual consolidation tended to be the same. Reinforced embankment safety coefficient is improved obviously, the failure mode changed, change characteristics and tensile strength of reinforcement, the strength and the interface geological conditions and other factors. Considering the large deformation characteristics obtained after the center shaft settlement and horizontal displacement of small slope deformation results were obviously decreased. The interfacial strength of shear stress level and influence on the stability of the interface, but the total deformation and reinforcement tension of reinforced embankment has no effect. The construction speed has a significant influence on gluten free the embankment and reinforced embankment can be quickly filled to a predetermined height. After the mechanism of reinforcement tension and interface shear stress level is greatly reduced considering indirect effects, improves the stability of the embankment.
(3) the stability analysis of soft foundation of limit equilibrium conditions of the reinforced embankment. Based on the traditional analysis method based on the combination of indirect effect mechanism of calculation model of the overall stability of reinforced embankment on soft foundation improvement of reinforced embankment is analyzed on the stability of the different calculation methods. The results show that the indirect effect of strength reduction mechanism and simplified Bishop method can reflect the reinforcement effect. Based on the strength reduction method and simplified Bishop method are in good agreement, and the Swedish slice method results have obvious difference with the safety coefficient is low and the reliability is not high. The sliding arc strength reduction method and simplified Bishop method more suitable for the analysis of contribution of reinforcement to stability.

【學(xué)位授予單位】：暨南大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2014
【分類號】：U416.1

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