【摘要】：膨脹土作為世界范圍內(nèi)廣泛分布的特殊土,對相關(guān)地區(qū)的工程建設(shè)造成了極大破壞和影響,一直是巖土工程領(lǐng)域研究的難題之一。淺層失穩(wěn)破壞是發(fā)生在鐵路、公路、水利等工程中最普遍最頻繁的膨脹土邊坡破壞現(xiàn)象,但目前對淺層失穩(wěn)破壞機理缺乏足夠的認識,傳統(tǒng)的極限平衡穩(wěn)定性分析方法不能如實反映和解釋膨脹土邊坡此類破壞的真實性狀,也制約了工程建設(shè)中如何采取合理有效的處理措施以解決由于其特殊性質(zhì)帶來的工程問題。因此,深入研究膨脹土邊坡的淺層失穩(wěn)破壞機理,并在此基礎(chǔ)上探討相應的工程措施是保障工程設(shè)計安全和經(jīng)濟性的關(guān)鍵。 本文結(jié)合南水北調(diào)中線工程的膨脹土邊坡穩(wěn)定問題,針對膨脹土最本質(zhì)的工程特性——膨脹性開展深入研究,通過大型靜力物理模型試驗,研究壓實膨脹土邊坡在沒有裂隙、超固結(jié)性、干濕循環(huán)等因素的影響下,由于水分入滲引起的邊坡膨脹變形和滑動的發(fā)生發(fā)展破壞全過程。在“濕度應力場”理論基礎(chǔ)上,提出一種非飽和滲流場-膨脹變形場-應力場的多場耦合數(shù)值分析方法,結(jié)合模型試驗和數(shù)值分析成果,闡述了膨脹土邊坡淺層失穩(wěn)的破壞機理。在此基礎(chǔ)上,從加筋土的筋—土作用機理出發(fā),研究土工格柵對膨脹土膨脹變形的約束效果,及其對邊坡淺層穩(wěn)定的改善作用,為確定合理的膨脹土工程處理措施提供理論依據(jù)。通過本文的研究,得到的主要結(jié)論如下： (1)針對膨脹土邊坡極為普遍的淺層失穩(wěn)破壞形式,采用大型物理模型試驗(6m×2m×2.8m),并結(jié)合濕度場-膨脹變形場-應力場的耦合數(shù)值模擬分析,揭示出膨脹土邊坡淺層失穩(wěn)的本質(zhì)在于膨脹土的膨脹性。由膨脹變形控制的膨脹土邊坡淺層漸進性失穩(wěn)破壞機理可闡述如下：膨脹土邊坡在受到外部水力邊界作用時,首先導致邊坡內(nèi)含水量場發(fā)生時空不均勻分布,繼而引起土體的不均勻膨脹變形,應力應變場發(fā)生重分布,在非飽和-飽和浸潤交界區(qū)域形成剪應力集中區(qū),產(chǎn)生局部剪切破壞,并逐漸向邊坡深部擴展,最終形成多重剪切面,邊坡發(fā)生漸進性失穩(wěn)破壞。 (2)針對膨脹土邊坡穩(wěn)定性分析,在“濕度應力場”理論基礎(chǔ)上,提出一種結(jié)合非飽和-飽和滲流場、膨脹變形場、應力場多場耦合作用的有限元數(shù)值分析方法,通過對模型試驗的仿真模擬,證明這種多場耦合分析模型和方法可以真實反映膨脹土邊坡的淺層漸進性失穩(wěn)過程,為深入理解邊坡淺層穩(wěn)定性的破壞機理提供了有用的分析手段。 (3)基于溫度膨脹和濕度膨脹的相似性,采用熱—固耦合有限元數(shù)值分析方法,根據(jù)室內(nèi)膨脹土無荷及有荷膨脹試驗成果,反演得到不同含水率、干密度和荷載作用下的膨脹系數(shù)變化規(guī)律。結(jié)果表明：膨脹系數(shù)受含水率、干密度、荷載等因素的綜合影響,在低荷載條件下含水率和膨脹系數(shù)近似符合線性關(guān)系。因此,在多場耦合數(shù)值計算中采用低荷載條件下對應的含水率—膨脹系數(shù)(飽和度—膨脹系數(shù))關(guān)系來反映邊坡不同部位濕度變化引起的膨脹系數(shù)的變化規(guī)律。 (4)采用大尺寸膨脹模型試驗,系統(tǒng)研究了鋪設(shè)土工格柵后膨脹土的吸濕膨脹變形發(fā)展規(guī)律,獲得了不同格柵參數(shù)(強度、類型、鋪設(shè)層數(shù)和方式等)對膨脹變形的影響規(guī)律,對土工格柵抑制膨脹變形的可行性進行了評價。 (5)通過大型物理模型試驗,對土工格柵處理膨脹土邊坡淺層穩(wěn)定的效果進行了研究,為膨脹土工程處理措施提供了基本的試驗依據(jù)。
[Abstract]:As a kind of special soil widely distributed in the world, expansive soil has caused great damage and influence to the engineering construction in the relevant area, and has been one of the difficult problems in the field of geotechnical engineering. The failure of the shallow-layer instability is the most common and most frequent expansive soil slope failure in the railway, highway, water conservancy, etc., but it is not enough to know the mechanism of the failure of the shallow layer. The traditional limit equilibrium stability analysis method can not faithfully reflect and explain the authenticity of such failure of the expansive soil slope, and also restrict the reasonable and effective treatment measures in the project construction to solve the engineering problems caused by the special properties. Therefore, the mechanism of shallow failure and failure of expansive soil slope is studied deeply, and the key to the safety and economy of engineering design is discussed. In this paper, the stability of expansive soil slope in the middle-line project of the South-to-North Water Transfer Project is discussed, and the most essential engineering property _ expansion of expansive soil is studied. Through the large-scale static physical model test, the slope of the compacted expansive soil is studied in the absence of cracks and supersolid. Under the influence of the factors such as the junction property, the dry-wet cycle and the like, the expansion and deformation of the side slope caused by the infiltration of water and the development of the sliding are destroyed. On the basis of the 鈥渉umidity stress field鈥，

本文編號：2316932